SimTX Wiki - User contributions [en]

SimTX Transmitter

2026-10-25T11:44:38Z

Clanker: Mark as the legacy Java client and point to the SimTX app

{{Documentation navigation}}

This page describes the legacy Java client. The SimTX app is the recommended client; start with [[Getting Started]] and the [[SimTX Guide]].

'''SimTX Transmitter''' is the operator client of the SimTX radio simulation platform. It lets a user configure a virtual radio station (callsign, location, transmitter, antenna) and transmit audio or data signals into a shared simulated radio spectrum hosted by a SimTX server. Receivers connected to the same server can tune to the transmission and hear it, subject to simulated antenna performance, propagation conditions and noise.

== Start with one task ==
New to SimTX? Follow [[Getting Started]] for downloading, account sign-in, and an audio-file transmission. No knowledge of antenna formulas or Lua is required.

The basic path is '''audio source → transmitter → simulated radio path → receiver'''. The transmitter app controls the station. A separate receiver lets a listener choose a frequency and hear the result. Both use the same server.

For a control you cannot identify, use [[Transmitter Interface]]. For a term you do not recognize, use [[Radio terms]].

All transmissions are simulated; no physical radio equipment is required.

== Overview ==
A transmitter session works as follows:

# The operator starts the application and signs in to a SimTX account, then selects an official server.
# The station is configured: callsign, geographic location, frequency, power, modulation, transmission source and antenna.
# The operator presses '''Start TX'''. The server admits, queues or rejects the session depending on its session limits.
# While the session runs, the Radio Deck shows live measured values: forward and reflected power, SWR, ALC, amplifier temperature and audio buffer level.
# The session ends when the source finishes, the operator stops it, or the server ends it.

== Main topics ==
* [[Getting Started]]: installation, connecting to a server, first transmission
* [[Transmitter Interface]]: reference for every control in the application window
* [[Modulation Modes]]: supported modes and their bandwidths
* [[Transmission Sources]]: audio files and URLs, microphone, white noise, PipeWire, GNU Radio IQ
* [[Lua extensions]]: modulation modes, audio add-ons, tools, themes, and libraries
* [[Extension catalog]]: shared extensions and complete station presets
* [[Radio Presets]]: built-in transmitter characteristics, from clean lab exciters to overdriven CB rigs
* [[Advanced Transmitter Settings]]: the fifteen fine-tuning parameters
* [[Station Configuration]]: callsign, location and saving station presets
* [[Antenna System]]: how antennas behave and are configured, with a page per antenna type
* [[Antenna Calculations]]: resonant lengths, SWR, gain and loss arithmetic
* [[SWR and Transmitter Protection]]: what happens when the antenna is mismatched
* [[Power Amplifier Behaviour]]: heating, power foldback and permanent damage
* [[Sessions and Queueing]]: admission, queue positions, rejections and kicks
* [[Propagation Basics]]: what determines whether a signal is heard at a distance

== What SimTX simulates ==
From the operator's point of view the simulation covers:
* Transmitter imperfections: compression, distortion, carrier leakage, hum, phase noise and more, selectable through [[Radio Presets]] or tuned individually.
* Realistic antennas: each antenna type has a genuine radiation pattern, feedpoint impedance and SWR that change with frequency, size, height and orientation. Custom antennas can be imported as NEC decks, see [[NEC File Import]].
* Amplifier thermodynamics: sustained transmission heats the finals, reduces output power and can permanently damage the amplifier, see [[Power Amplifier Behaviour]].
* Radio propagation between stations, including ionospheric effects, time of day and distance, see [[Propagation Basics]].

[[Category:SimTX]]

Propagation Basics

2026-10-25T11:44:30Z

Clanker: Remove the storm Doppler drift claim; add VHF, UHF and satellites

{{Documentation navigation}}

SimTX simulates realistic radio propagation between stations, including the ionosphere, time of day, season, solar and geomagnetic activity, ground quality and receiver noise. This page explains, from the operator's point of view, what determines whether a transmission is heard at a given distance.

== Check reception in a useful order ==
# First verify the transmitted audio with '''Listen to Own TX'''. That monitor is before propagation.
# On the receiver, confirm the same server, frequency, mode, and suitable bandwidth.
# Check the distance and direction between the two simulated stations.
# Try a frequency appropriate to the time of day and path, then retune the antenna.
# Compare reception before increasing power.

For nearby reception, the ground path matters. For many longer HF paths, the ionosphere must return the signal toward Earth. A station can therefore be heard far away but missed at an intermediate distance. The sections below explain this without requiring a propagation calculation.

== Two ways a signal travels ==
* '''Groundwave''': the signal follows the ground outward from the antenna. It dominates short range (out to a few tens of kilometers on all bands, farther on lower frequencies) and favours '''vertically polarized''' antennas and good ground (sea water is best). Groundwave range shrinks quickly as frequency rises; on the higher HF bands it is essentially local.
* '''Skywave''': the signal refracts off the ionosphere and returns to Earth hundreds to thousands of kilometers away. This is how HF covers distance. Multiple hops extend the range further at the cost of extra loss.

Between the end of groundwave and the first skywave return there can be a '''skip zone''' where the station is inaudible even though it is heard both closer and farther away.

== The frequency window: LUF and MUF ==
For any skywave path at any moment there is a usable frequency window:
* Above the '''maximum usable frequency (MUF)''' the ionosphere no longer bends the signal back; it escapes into space.
* Below the '''lowest usable frequency (LUF)''' absorption in the lower ionosphere eats the signal.
The window moves constantly:
* The MUF rises with solar activity and during daytime, and is generally higher on paths toward the equator than at high latitudes.
* The LUF rises during daylight (absorption is a daytime phenomenon) and drops at night, when very low frequencies open up.
* Frequencies just below the MUF usually propagate best; deep inside the window absorption grows toward the low end.

Rules of thumb that follow directly:
* '''Low bands (below about 5 MHz)''': night-time and short-to-medium range in daytime. Daytime long-distance work is largely absorbed.
* '''Middle bands (5 to 12 MHz)''': can be workable day and night, depending on the path. The default 4625 kHz is 4.625 MHz and belongs to the lower-frequency example above.
* '''High bands (above about 14 MHz)''': daytime and high solar activity; they close at night.
* Around dawn and dusk (the grey line), low and middle band paths along the terminator are enhanced.

== Short range via the ionosphere: NVIS ==
Coverage from roughly 50 to 500 km needs radiation that goes almost straight up and reflects back down (near-vertical incidence skywave). It requires a frequency comfortably below the vertical MUF (typically 2 to 8 MHz depending on conditions) and a '''high-angle antenna''': a low dipole, inverted-V or loop. This is the regime where "worse" antennas outperform beams.

== Long range ==
Distances beyond about 1000 km leave the antenna at '''low elevation angles'''. What helps: a low takeoff antenna (Yagi, vertical, high dipole), a frequency near the path MUF, and daylight positioning appropriate to the band. Multi-hop paths add loss per hop, so more power or better antennas are needed as distance grows.

== VHF, UHF and satellites ==
Above about 30 MHz the ionosphere rarely returns signals, so range depends on the line of sight.
* Hills and mountains block or diffract the signal. SimTX uses a 150 m terrain map, so a station behind a ridge hears less than one on top of it.
* Antenna height and a clear horizon matter more than power.
* Satellites are heard only while above the horizon. Their signal shifts in frequency during a pass (Doppler), most on the higher bands; see [[SimTX Guide/Satellites|Satellites]].

== Noise at the receiver ==
Whether a signal is readable depends on how far it sits above the receiving station's noise floor:
* '''Atmospheric noise''' dominates the low bands and is much stronger at night and in disturbed conditions.
* '''Man-made noise''' depends on the receiver environment; a city location can be tens of decibels noisier than a quiet rural one.
* Noise grows with receiver bandwidth: narrow modes hear deeper.

== Mode sensitivity ==
Approximate signal-to-noise ratios needed for readable copy, from most to least sensitive:
{| class="wikitable"
! Mode !! Approximate required SNR
|-
| CW || around 0 dB
|-
| SSB (USB/LSB) || about 6 dB
|-
| AM || 8 to 10 dB
|-
| NFM / WFM || about 12 dB
|}
The spread matters: a path hopeless for FM can still carry CW comfortably. Narrow modes are the best probes of marginal propagation.

== Disturbances and fading ==
* Geomagnetic storms raise absorption, depress the MUF and destabilize high-latitude paths.
* Even on quiet days skywave signals fade continuously (multipath fading); deep fades of many decibels are normal and average out over time.
* Sporadic E can open surprising mid-range paths on high frequencies, mainly in local summer.

== Checklist: will I be heard at distance X? ==
# Under about 50 km: almost any setup works; vertical polarization helps most.
# 50 to 500 km: use a low band frequency below the day's vertical MUF and a high-angle antenna (NVIS).
# 500 to 3000 km: pick a band whose window is open for the time of day (lower at night, higher by day); a dipole at good height works.
# Beyond 3000 km: choose a frequency near the path MUF, use a low-takeoff antenna aimed at the target, and prefer sensitive modes.
# Always compare the required SNR of the mode with realistic noise at the receiving end; when in doubt, drop to a narrower mode rather than raising power.

[[Category:SimTX]]

SimTX API/Station endpoints

2026-10-25T11:44:19Z

Clanker: Station lists carry deck digests only; removed decks are not kept; rig values use the game ranges

{{SimTX API navigation}}
The '''station endpoints''' of the [[SimTX API/Account service|account service]] create, read, edit and delete an account's persistent [[SimTX API/Stations|stations]], launch [[SimTX API/Satellites|satellites]] and deorbit them. A station belongs to the account, not to a game server; game sessions attach to it with a station-bound [[SimTX API/Game tickets|game ticket]].

All endpoints take a bearer credential (an access credential or a personal credential) on <code><nowiki>https://auth.simtx.net</nowiki></code>. Service credentials are refused with <code>403 account_credential_required</code>.

== Endpoints ==
{| class="wikitable"
! Method and path !! Scope !! Result
|-
| <code>GET /api/v1/stations</code> || Any || <code>200 {"stations": [Station]}</code>: your stations
|-
| <code>POST /api/v1/stations</code> || <code>station.manage</code> || <code>201 Station</code>: create a ground station
|-
| <code>GET /api/v1/stations/{id}</code> || Any || <code>200 Station</code>
|-
| <code>PATCH /api/v1/stations/{id}</code> || <code>station.manage</code> || <code>200 Station</code>
|-
| <code>DELETE /api/v1/stations/{id}</code> || <code>station.manage</code> || <code>204</code>
|-
| <code>POST /api/v1/stations/{id}/antennas</code> || <code>station.manage</code> || <code>201 Station</code> (ground stations only)
|-
| <code>PATCH</code>, <code>DELETE /api/v1/stations/{id}/antennas/{antennaId}</code> || <code>station.manage</code> || <code>200 Station</code>
|-
| <code>POST /api/v1/stations/{id}/rigs</code> || <code>station.manage</code> || <code>201 Station</code> (ground stations only)
|-
| <code>PATCH</code>, <code>DELETE /api/v1/stations/{id}/rigs/{rigId}</code> || <code>station.manage</code> || <code>200 Station</code>
|-
| <code>POST /api/v1/satellites</code> || <code>station.manage</code> || <code>201 Station</code>: launch a satellite
|-
| <code>POST /api/v1/stations/{id}/deorbit/preview</code> || Any || <code>200 Deorbit</code>: what a burn now would do
|-
| <code>POST /api/v1/stations/{id}/deorbit</code> || <code>station.manage</code> || <code>200 Station</code>: fire the deorbit burn
|-
| <code>GET /api/v1/satellites</code> || None (public) || <code>200 {"satellites": [SatelliteCatalogEntry]}</code>; see [[SimTX API/Public endpoints#Public satellites|Public endpoints]]
|}

"Any" means any account credential, without a particular scope. A write with a credential whose scope lacks <code>station.manage</code> is refused with <code>403 scope_required</code> and <code>fieldErrors.scope = "station.manage"</code>; sign the user in again with the wider scope. An account without the permission gets <code>403 permission_denied</code>. Rate limits: 240 reads and 120 writes per minute per IP address.

== The Station object ==
<syntaxhighlight lang="json">
{
"stationId": "3f2504e0-4f89-41d3-9a0c-0305e82c3301",
"ownerAccountId": "0f8e2c4a-1b3d-4e5f-8a9b-0c1d2e3f4a5b",
"ownerHandle": "n0call",
"kind": "GROUND",
"state": "ACTIVE",
"name": "Home",
"callsign": "N0CALL",
"visibility": "UNLISTED",
"revision": 3,
"limits": { "maxSessions": 16, "maxTransmitters": 4, "maxReceivers": 16 },
"location": { "latitudeDeg": 47.4979, "longitudeDeg": 19.0402, "altitudeMeters": 120.0 },
"antennas": [
{
"antennaId": "9b2c1e47-2f0a-4c55-8d1e-6a7b8c9d0e1f",
"name": "40 m dipole", "ordinal": 0, "revision": 1,
"type": "DIPOLE", "heightMeters": 10.0, "azimuthDeg": 90.0,
"feedlineLossDb": 1.0, "wireLengthMeters": 0.0, "mount": "FIXED"
}
],
"rigs": [
{
"rigId": "c41d7a52-0e3b-4f6a-9c8d-1b2a3c4d5e6f",
"name": "100 W transceiver", "revision": 1,
"paMaxWatts": 100.0, "noiseFigureDb": 6.0,
"tx": { "carrierLeakDb": 55.0, "oppositeSidebandSuppressionDb": 50.0 }
}
],
"createdAt": "2026-10-24T12:00:00Z",
"updatedAt": "2026-10-24T12:30:00Z"
}
</syntaxhighlight>

{| class="wikitable"
! Field !! Type !! Description
|-
| <code>stationId</code> || string (UUID) || Never changes.
|-
| <code>ownerAccountId</code>, <code>ownerHandle</code> || string || The owning account.
|-
| <code>kind</code> || string || <code>GROUND</code> or <code>SATELLITE</code>.
|-
| <code>state</code> || string || <code>ACTIVE</code>, <code>DEORBITING</code> or <code>DEORBITED</code>. Ground stations are always <code>ACTIVE</code>.
|-
| <code>name</code>, <code>callsign</code> || string || 1 to 64 characters each.
|-
| <code>visibility</code> || string || <code>PUBLIC</code> or <code>UNLISTED</code>. See [[SimTX API/Stations#Visibility|Visibility]].
|-
| <code>revision</code> || integer || Increases with every edit of the station.
|-
| <code>limits</code> || object || <code>maxSessions</code>, <code>maxTransmitters</code>, <code>maxReceivers</code>, each 0 to 10,000, clamped to the owner's <code>game.station_sessions.N</code>.
|-
| <code>location</code> || object || Ground stations: <code>latitudeDeg</code> (−90 to 90), <code>longitudeDeg</code> (−180 to 180), <code>altitudeMeters</code> (−500 to 10,000).
|-
| <code>orbit</code>, <code>attitude</code> || object || Satellites. See [[#Orbit and attitude|Orbit and attitude]].
|-
| <code>deorbit</code> || object || Satellites whose deorbit burn has fired. See [[#Deorbiting|Deorbiting]].
|-
| <code>antennas</code> || array || 1 to 8 antennas (satellites: 1 to 4). See [[#Antennas and rigs|Antennas and rigs]].
|-
| <code>rigs</code> || array || 0 to 8 rigs.
|-
| <code>createdAt</code>, <code>updatedAt</code>, <code>launchedAt</code>, <code>deorbitedAt</code> || string || Timestamps; <code>launchedAt</code> and <code>deorbitedAt</code> for satellites.
|}

=== Antennas and rigs ===
An '''antenna''' has <code>antennaId</code>, <code>name</code> (at most 64 characters), <code>ordinal</code> (its position; the first antenna is the default for tickets), <code>revision</code>, and the fields of the game protocol's [[SimTX API/Data types#AntennaConfig|AntennaConfig]] in camelCase:

{| class="wikitable"
! Field !! Description
|-
| <code>type</code> || An [[SimTX API/Data types#Antenna types|antenna type]] name.
|-
| <code>heightMeters</code> || ≥ 0. Default 10 for ground stations, 0 for satellites.
|-
| <code>azimuthDeg</code> || −360 to 360.
|-
| <code>feedlineLossDb</code> || ≥ 0. Default 1 for ground stations, 0 for satellites.
|-
| <code>wireLengthMeters</code> || ≥ 0. 0 sizes the template for the operating frequency.
|-
| <code>necDeck</code> || Optional NEC-2 deck, at most 262,144 bytes; replaces the template. Satellite decks must not contain a <code>GN</code> card. Responses add <code>necDeckSha256</code>, the hex SHA-256 of the deck. Station lists carry only <code>necDeckSha256</code>; read the station for the deck text. A removed antenna, a deleted station and a reentered satellite keep no deck.
|-
| <code>mount</code> || <code>FIXED</code> (default), <code>AZ</code> or <code>AZEL</code>.
|-
| <code>pointing</code> || Steerable mounts only: <code>mode</code> (<code>FIXED</code> or <code>TRACK</code>), <code>azimuthDeg</code> (−360 to 360), <code>elevationDeg</code> (−90 to 90), <code>targetStationId</code> (required for <code>TRACK</code>), <code>azimuthRateDegPerSec</code> and <code>elevationRateDegPerSec</code> (0 to 360; 0 = default). A <code>FIXED</code> mount stores no pointing. See [[SimTX API/Tracking and pointing]].
|}

A '''rig''' is a saved radio profile: <code>rigId</code>, <code>name</code>, <code>revision</code>, <code>paMaxWatts</code> (0 to 10,000,000; default 100), <code>noiseFigureDb</code> (0 to 100; default 6), and <code>tx</code>, an object with the fifteen [[SimTX API/Data types#TxImperfections|transmitter imperfection]] values in camelCase (<code>finalDriveDb</code>, <code>paHeadroomDb</code>, <code>audioCompressionDb</code>, <code>paSoftness</code>, <code>paAmPmDeg</code>, <code>carrierLeakDb</code>, <code>oppositeSidebandSuppressionDb</code>, <code>frequencyOffsetHz</code>, <code>mainsHumDb</code>, <code>mainsHumHz</code>, <code>amModulationIndex</code>, <code>paSupplySagDb</code>, <code>txNoiseFloorDb</code>, <code>oscillatorPhaseNoiseDb</code>, <code>cwKeyRiseMs</code>). Values left out take the generic HF preset. Each value must lie in the range the game accepts (see [[SimTX API/Data types#TxImperfections|TxImperfections]]); other values are refused with <code>400 station_invalid</code>.

=== Orbit and attitude ===
<code>orbit</code> holds the mean elements of the [[SimTX API/Satellites#Orbit model|simtx-j2-v1]] model: <code>model</code> (<code>simtx-j2-v1</code>), <code>epoch</code> (read-only), <code>semiMajorAxisKm</code>, <code>eccentricity</code>, <code>inclinationDeg</code>, <code>raanDeg</code>, <code>argumentOfPerigeeDeg</code>, <code>meanAnomalyDeg</code>.

<code>attitude</code> has a <code>mode</code> of <code>NADIR</code>, <code>INERTIAL</code> or <code>SPIN</code> and the fields of that mode: <code>yawDeg</code>; <code>rightAscensionDeg</code>, <code>declinationDeg</code> (−90 to 90), <code>rollDeg</code>; or <code>spinAxis</code> (<code>NADIR</code>, <code>ORBIT_NORMAL</code>, <code>VELOCITY</code>), <code>spinRateRpm</code> (0 to 60), <code>spinPhaseDeg</code>. See [[SimTX API/Satellites#Attitude|Attitude]].

== Listing stations ==
<code>GET /api/v1/stations</code> returns the account's stations, ground and satellite, including deorbited satellites that have not been deleted.

<syntaxhighlight lang="bash">
curl -s https://auth.simtx.net/api/v1/stations -H "Authorization: Bearer $SIMTX_TOKEN"
</syntaxhighlight>

Antennas in the list carry <code>necDeckSha256</code> but no <code>necDeck</code>; <code>GET /api/v1/stations/{id}</code> returns the deck text.

== Creating a ground station ==
<code>POST /api/v1/stations</code>

<syntaxhighlight lang="json">
{
"name": "Home",
"callsign": "N0CALL",
"visibility": "UNLISTED",
"location": { "latitudeDeg": 47.4979, "longitudeDeg": 19.0402, "altitudeMeters": 120.0 },
"antennas": [ { "name": "40 m dipole", "type": "DIPOLE", "heightMeters": 10.0, "azimuthDeg": 90.0 } ],
"rigs": [ { "name": "100 W transceiver", "paMaxWatts": 100.0, "noiseFigureDb": 6.0 } ]
}
</syntaxhighlight>

<code>name</code>, <code>callsign</code>, <code>location</code> and at least one antenna are required. <code>visibility</code> defaults to <code>UNLISTED</code>, <code>limits</code> to 16 sessions, 4 transmitters and 16 receivers before clamping. A ground station is often a real address: clients should keep the UNLISTED default unless the user chooses otherwise.

== Reading, editing and deleting ==
* <code>GET /api/v1/stations/{id}</code> returns one station. Another account's station is <code>404 station_not_found</code>.
* <code>PATCH /api/v1/stations/{id}</code> takes any of <code>name</code>, <code>callsign</code>, <code>visibility</code>, <code>limits</code> and, for ground stations, <code>location</code>. Omitted fields keep their values. There is no cooldown on location changes.
* <code>DELETE /api/v1/stations/{id}</code> deletes a ground station, or a satellite that has reentered (<code>DEORBITED</code>). An active or deorbiting satellite is refused with <code>409 satellite_active</code>.

Every edit increases the station's <code>revision</code>. Sessions bound to the station either continue with the new values or end; see [[SimTX API/Stations#Edits while sessions run|Edits while sessions run]].

=== Antennas and rigs ===
Ground stations only; a launched satellite is sealed.
* <code>POST /api/v1/stations/{id}/antennas</code> adds an antenna (at most 8). <code>PATCH .../antennas/{antennaId}</code> changes one; omitted fields keep their values. <code>DELETE .../antennas/{antennaId}</code> removes one; the last antenna cannot be removed (<code>409 last_antenna</code>).
* <code>POST /api/v1/stations/{id}/rigs</code> adds a rig (at most 8). <code>PATCH .../rigs/{rigId}</code> changes one; a <code>tx</code> object replaces the stored imperfection values as a whole. <code>DELETE .../rigs/{rigId}</code> removes one.

Each returns the whole station.

== Launching a satellite ==
<code>POST /api/v1/satellites</code>

<syntaxhighlight lang="json">
{
"name": "SimSat-1",
"callsign": "SSAT1",
"visibility": "PUBLIC",
"orbit": {
"model": "simtx-j2-v1",
"semiMajorAxisKm": 6921.0, "eccentricity": 0.001, "inclinationDeg": 97.6,
"raanDeg": 120.0, "argumentOfPerigeeDeg": 90.0, "meanAnomalyDeg": 10.0
},
"attitude": { "mode": "NADIR", "yawDeg": 0.0 },
"antennas": [ { "name": "70 cm turnstile", "type": "TURNSTILE" } ],
"rigs": [ { "name": "Beacon", "paMaxWatts": 2.0, "noiseFigureDb": 2.0 } ]
}
</syntaxhighlight>

* <code>name</code>, <code>callsign</code>, <code>orbit</code> and 1 to 4 antennas are required; up to 8 rigs.
* The orbit is sent without <code>epoch</code>. The account service sets the epoch to the launch instant and interprets the elements at that instant.
* The orbit must pass [[SimTX API/Satellites#Validation|validation]]: model <code>simtx-j2-v1</code>, perigee at least 200 km and apogee at most 40,000 km above the 6,371 km sphere, 0 ≤ ''e'' < 1, 0 ≤ ''i'' ≤ 180°, finite angles, spin rate 0 to 60 rpm.
* Satellite antennas are modelled in free space; their NEC decks must not contain a <code>GN</code> card.
* After launch the satellite is '''sealed''': only <code>name</code>, <code>callsign</code>, <code>visibility</code> and <code>limits</code> can change. Changes to the orbit, attitude, antennas or rigs are refused with <code>409 station_sealed</code>.

== Deorbiting ==
* <code>POST /api/v1/stations/{id}/deorbit/preview</code> returns the <code>Deorbit</code> object that a burn fired now would produce, without changing anything. It needs no particular scope. Use it to show the user when and where the satellite would reenter before they confirm.
* <code>POST /api/v1/stations/{id}/deorbit</code> fires the burn and returns the station, now <code>DEORBITING</code>, with its <code>orbit</code> replaced by the post-burn elements (epoch = burn time) and <code>deorbit</code> set. The burn is irreversible.

<syntaxhighlight lang="json">
{
"burnAt": "2026-10-24T12:00:00Z",
"reentryAt": "2026-10-24T12:29:00Z",
"reentryLocation": { "latitudeDeg": -12.3, "longitudeDeg": 101.7, "altitudeMeters": 80000.0 },
"deltaVMps": 189.0,
"orbit": {
"model": "simtx-j2-v1", "epoch": "2026-10-24T12:00:00Z",
"semiMajorAxisKm": 6596.0, "eccentricity": 0.0493, "inclinationDeg": 97.6,
"raanDeg": 120.4, "argumentOfPerigeeDeg": 270.0, "meanAnomalyDeg": 180.0
}
}
</syntaxhighlight>

{| class="wikitable"
! Field !! Description
|-
| <code>burnAt</code> || When the burn fires (or fired).
|-
| <code>reentryAt</code> || The first time after the burn that the height drops below 80 km. Sessions on the satellite end then, and it becomes <code>DEORBITED</code>.
|-
| <code>reentryLocation</code> || The sub-satellite point at <code>reentryAt</code>; <code>altitudeMeters</code> is the 80 km interface.
|-
| <code>deltaVMps</code> || Velocity change of the burn, m/s.
|-
| <code>orbit</code> || The exact post-burn elements (epoch = <code>burnAt</code>) that the service stores, or would store. Draw the fall from them; do not re-plan the burn.
|}

The values in the example are illustrative. Deorbiting a satellite that is already deorbiting is refused with <code>409 already_deorbiting</code>, one that has reentered with <code>409 station_inactive</code>, and a ground station with <code>400 station_invalid</code>. See [[SimTX API/Satellites#Deorbit|Deorbit]].

== Quotas ==
The number of stations an account may own is capped by numeric capabilities of the account: <code>game.owned_stations.N</code> for all active stations, ground and satellite, and <code>game.owned_satellites.N</code> for active satellites. Deorbiting satellites count until they reenter. <code>game.station_sessions.N</code> caps a station's session limits. Defaults: members 100, 25 and 16; supporters 500, 100 and 64. There are no cooldowns. A creation over a quota is refused with <code>409 station_quota_exceeded</code>, with <code>fieldErrors.capability</code> and <code>fieldErrors.limit</code>.

== Errors ==
{| class="wikitable"
! HTTP !! <code>code</code> !! Meaning
|-
| 400 || <code>station_invalid</code> || A field is invalid; <code>message</code> and <code>fieldErrors</code> name it.
|-
| 403 || <code>scope_required</code> || The credential's scope lacks <code>station.manage</code>.
|-
| 403 || <code>permission_denied</code> || The account lacks <code>station.manage</code>.
|-
| 403 || <code>account_credential_required</code> || A service credential was used.
|-
| 404 || <code>station_not_found</code> || Unknown station, or not yours.
|-
| 409 || <code>station_sealed</code> || The change would modify a launched satellite.
|-
| 409 || <code>station_inactive</code> || The satellite has reentered.
|-
| 409 || <code>last_antenna</code> || A station keeps at least one antenna.
|-
| 409 || <code>station_quota_exceeded</code> || <code>fieldErrors</code> name the capability and its limit.
|-
| 409 || <code>satellite_active</code> || Delete refused; deorbit the satellite and wait for its reentry first.
|-
| 409 || <code>already_deorbiting</code> || The burn has already fired.
|-
| 413 || <code>request_too_large</code> || The body is over 2 MiB.
|}

{{SimTX API navbox}}
[[Category:SimTX API]]
[[Category:SimTX API account service]]

Main Page

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__NOTOC__
<div style="border:1px solid #a2a9b1; border-top:4px solid #36c; padding:1em 1.4em; margin-bottom:1.2em;">
<span style="font-size:180%;">SimTX Wiki</span>

'''SimTX is a shared radio simulation.''' You set up virtual stations, transmit audio and listen with an SDR program. Distance, antennas and radio conditions change what listeners hear.

</div>

== Getting started ==
'''[[Getting Started]]''': install the app, sign in, create a station, transmit and listen.

== User guides ==
* '''[[SimTX Guide/Transmitting|Transmitting]]''' and '''[[SimTX Guide/Receiving|Receiving]]''': the Transmit and Receive tabs.
* '''[[SimTX Guide/Stations|Stations]]''': your stations, antennas and radios.
* '''[[SimTX Guide/Satellites|Satellites]]''': launch a satellite, follow its passes and deorbit it.
* '''[[SimTX Guide/Rotators and tracking|Rotators and tracking]]''': turn an antenna or follow a satellite.
* '''[[SimTX Guide/Map and coverage|Map and coverage]]''': the globe, station lists and coverage maps.
* '''[[SimTX Guide/Catalog and add-ons|Catalog and add-ons]]''', '''[[SimTX Guide/Health|Health]]''', '''[[SimTX Guide/Settings and shortcuts|Settings and shortcuts]]''' and '''[[SimTX Guide/Troubleshooting|Troubleshooting]]'''.
All guides are listed on [[SimTX Guide]].

== For developers ==
The [[SimTX API]] reference documents the account service and the game protocol, message by message. Start with the [[SimTX API/Quick start|quick start]].

== Learn in order ==
# '''[[SimTX Guide/Transmitting|Find your way around]]''': the Transmit tab's controls and meters. The Java transmitter's window is described on [[Transmitter Interface]].
# '''[[Transmission Sources|Choose what to send]]''': play a file, use a microphone, or send a stream.
# '''[[Antenna System|Change frequency and coverage]]''': choose and adjust an antenna, then learn [[Propagation Basics|why reception changes]].
# '''[[Lua extensions|Add features]]''': install modes, audio processors, tools, and themes without writing code.
# '''[[How to receive|Receive]]''': listen with any [[wikipedia:Software-defined_radio|SDR]] program.

[[File:SimTX Transmitter desktop app.png|thumb|center|850px|alt=SimTX desktop app window on the Stations tab: a globe of Europe and Africa with Demo hilltop, an orange TX beam at 300°, a blue RX beam at 180°, dashed lines to satellites, orbit rings, and the station's details in the sidebar.|The SimTX desktop app on the Stations tab, with a station on air, its beam headings and the satellites in view.]]

== Find a specific answer ==
* '''Nothing happens or no sound?''' See [[SimTX Guide/Troubleshooting|Troubleshooting]], or [[Troubleshooting]] for the Java transmitter.
* '''Which radio mode should I choose?''' See [[Modulation Modes]].
* '''How do I save or share my station setup?''' See [[SimTX Guide/Stations|Stations]] and [[Extension catalog]]. For the Java transmitter, see [[Station Configuration]].
* '''What do SWR, bandwidth, and IQ mean?''' See [[Radio terms]].
* '''Looking for formulas or the Lua API?''' See the [[Documentation|documentation index]].

== Community and other ways to use SimTX ==
* [[:Category:Radio Stations|Community radio stations]]: stations described by their operators.
* [[Guide to setting up sdr console with simtx|SDR Console]], [[DATV RX Tutorial|digital television reception]], [[DATV TX Tutorial|digital television transmission]], [[How to receive]] and [[DRM TX tutorial|DRM transmission]]: additional community guides.
* [[Getting Started#1. Install the app|Download the desktop app]]
* [https://simtx.net/downloads Download the Java transmitter]
* [https://simtx.net SimTX website]
* [https://discord.gg/BxtpFJAs6c SimTX Discord]

SimTX Guide/Troubleshooting

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{{SimTX Guide navigation}}
Problems in the SimTX desktop app, with the messages the app shows and what to do.

== Signing in ==
{| class="wikitable"
! Message !! What to do
|-
| ''Device authorization expired; try again.'' || Press '''Sign in''' again and approve the device in the browser within the time shown.
|-
| ''Couldn't check sign-in'' || Check your internet connection and try again.
|-
| ''Sign in again to create and edit stations.'' || Press '''Sign in''' and approve the device again.
|-
| ''Sign in to transmit from a station'' || Transmitting needs a SimTX account. Press '''Sign in'''.
|}

== Connecting ==
[[File:SimTX Guide Troubleshooting connection details.png|thumb|center|342px|alt=Connection details for SimTX Demo marked Good: latency 38 ms, jitter 4 ms, download and upload rates, server replies steady, TX buffer at server 1340 ms, no reconnects, and Disconnect and Change server buttons.|Connection details for a good link to the server.]]
{| class="wikitable"
! Message !! What to do
|-
| ''No servers online'' || No server is running at the moment. Press '''Retry''' later.
|-
| ''Couldn't load the server list'' || Check your internet connection and press '''Retry'''.
|-
| ''Couldn't connect to'' a server || Choose another server, or try again later.
|-
| ''Not connected to a server'' || Press '''Connect''' in the top right of the window.
|}

The connection strip in the top right shows the link quality: '''Good''', '''Fair''', '''Unstable''', '''Poor''', '''Not responding''' or '''Offline'''. Select it to see why:
{| class="wikitable"
! Item !! Trouble when
|-
| '''Server replies''' || The server has been silent for a while.
|-
| '''TX buffer at server''' || Below about 300 ms; listeners may hear gaps.
|-
| '''RX dropouts (1 min)''' || Your receive bridges lost data.
|-
| '''Reconnects (1 min)''' || The connection dropped and came back.
|-
| '''Jitter''' || Above about 80 ms.
|-
| '''Latency''' || Above a second.
|}

'''Settings''', '''Connection''', '''Reconnect automatically''' reconnects after a drop.

== Before Start TX ==
Messages beside '''Start TX''' block the start until fixed. Most have a button that fixes them.
{| class="wikitable"
! Message !! Fix
|-
| ''Create a station to transmit from'' || '''Create''' opens the station editor. See [[SimTX Guide/Stations|Stations]].
|-
| ''Choose a station to transmit from'' || Choose one under '''Transmit from'''.
|-
| ''No frequency'' || Enter a '''Frequency'''.
|-
| ''Power must be above 0 W'' || Enter a '''Power (W)'''.
|-
| ''Power is above'' the radio's ''cap'' || '''Use cap''' sets the power to the radio's power cap.
|-
| ''No audio file chosen'' || Press '''Choose…''' under '''Source'''.
|-
| ''No input device selected'' || Choose an '''Input device'''.
|-
| ''GNU Radio IQ port is invalid'' || Enter a port from 1 to 65535.
|-
| ''High SWR'' || Warning: only part of the power reaches the antenna. '''Change antenna''', or adjust its length in the station editor.
|-
| ''No input devices detected'' || Warning: connect a microphone or audio interface. On macOS, allow SimTX under System Settings, Privacy and Security, Microphone.
|-
| ''The tracked satellite no longer exists'' || Warning: choose another target under '''Track a satellite'''.
|}

== Before Start RX ==
{| class="wikitable"
! Message !! Fix
|-
| ''No callsign'' || Enter a '''Callsign''' for ad-hoc listening.
|-
| ''Receive location is invalid'' || '''Pick on map''', or enter the latitude and longitude.
|-
| ''Choose one of your stations'' or ''Choose a public station'' || Choose the station under '''Where you listen'''.
|-
| ''No center frequency'', ''Sample rate must be above 0'' || Fill in '''Tuning'''.
|-
| ''rtl_tcp port must be 1 to 65535'' || Enter a valid '''rtl_tcp port'''.
|-
| ''Listen address must be an IP like 127.0.0.1 or 0.0.0.0'' || Correct the '''Listen address'''.
|-
| ''Bridge is reachable from your network, so anyone there can retune it'' || Warning: '''Local only''' sets the address to 127.0.0.1.
|}

== Session messages ==
The '''Sessions''' list shows each transmission's state and message. [[SimTX Guide/Transmitting#Sessions|Transmitting]] lists the states.
{| class="wikitable"
! Message !! Meaning
|-
| '''Queued''' || All transmitter slots are taken. Leave it; it starts when a slot is free.
|-
| ''Rejected:'' and a reason || The server refused the start. The reason says why, for example ''Only the station's owner can transmit through it''.
|-
| ''Failed: TX idle timeout'' || The audio source sent nothing for 15 seconds. Check the file or input device.
|-
| ''Failed: connection error'' || The connection to the server broke. Start the transmission again.
|-
| ''Reconnecting TX…'' || The app is restoring the session after a drop.
|-
| ''Reconnect failed:'' and a reason || The session couldn't be restored. Start it again.
|-
| ''Kicked:'' and a reason || The server ended the session, for example a moderator, a deleted station or a satellite reentry.
|}

A banner across the top of the window shows notices from the server. A banner starting with ''Banned:'' means your address is banned; the text gives the reason.

== Nothing heard ==
On the receiving side:
# Check that the bridge is '''Running''' in the '''Bridges''' list.
# Check that your SDR program is connected to the address and port shown under '''Bridge'''.
# Check that the signal is inside the band: the '''Center frequency''' plus or minus half the '''Sample rate'''.
# Set the SDR program's mode and bandwidth to match the transmission.
# Consider propagation: distance, band and time of day decide whether a signal gets through. See [[Propagation Basics]].
# For a directional antenna, check where it points. See [[SimTX Guide/Rotators and tracking|Rotators and tracking]].
# For a satellite, check that a pass is in progress and that '''Correct Doppler''' is ticked. A satellite low on the horizon can be hidden by hills.

On the transmitting side:
# Check that the session is '''Running''', not '''Queued''' or '''Paused'''.
# Press '''Listen to own TX''' to check the audio.
# Check the radio deck: '''BUF/s''' above zero, '''SWR/:1''' low and '''FWD/W''' near the power you set.
# Check that the listener is on the same server.

== Catalog ==
{| class="wikitable"
! Message !! What to do
|-
| ''Connect to a server to browse the catalog.'' || Connect, then open the '''Catalog''' tab again.
|-
| ''No answer from the server.'' || Press '''Retry'''.
|-
| ''The server didn't send the files in 10 s.'' || Press '''Retry'''.
|-
| ''No answer from the server in 20 s; check the catalog before trying again.'' || Refresh the catalog to see whether the upload arrived before publishing again.
|-
| ''Publishing requires catalog.publish'' || Your account doesn't have permission to publish.
|}

== See also ==
* [[How to receive]]
* [[SWR and Transmitter Protection]]
* [[Power Amplifier Behaviour]]

[[Category:SimTX Guide]]

SimTX Guide/Settings and shortcuts

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{{SimTX Guide navigation}}
The '''Settings''' tab has a section list on the left.

== General ==
[[File:SimTX Guide Settings general.png|thumb|center|800px|alt=Settings with the section list on the left and General open: Theme, Map quality, the Help items Getting started guide, What's new, Hints and Guides, and the Keyboard shortcut list.|Settings, General, with the theme, map quality, help items and keyboard shortcuts.]]
{| class="wikitable"
! Setting !! What it does
|-
| '''Theme''' || '''Match system''', '''Dark''', '''Light''', or a theme from an extension.
|-
| '''Map quality''' || '''Auto''', '''Full''' or '''Light'''. See [[SimTX Guide/Map and coverage#Map quality|Map and coverage]].
|-
| '''Window title bar''' || Windows and Linux: '''SimTX (custom)''' or '''Window manager (native)'''.
|}

'''Help''':
{| class="wikitable"
! Item !! What it does
|-
| '''Getting started guide''' || '''Show again''' restarts the in-app guide to connecting, choosing a station and going on air.
|-
| '''What's new''' || '''Show''' opens the What's new sheet with the latest features.
|-
| '''Hints''' || '''Reset hints''' shows the short tips on new controls again.
|-
| '''Guides''' || '''Open guides''' opens these wiki guides in your browser.
|}

'''Keyboard''' lists the shortcuts (see below).

== Audio ==
'''Override wire sample rate''' replaces the automatic audio rate sent to the server with one you choose: 44.1k, 48k, 96k, 192k, 384k or a value in Hz. A higher rate uses more upload bandwidth and can cause gaps on a slow link.

== Connection ==
* '''Server''' shows the server you are connected to, with '''Disconnect''' and '''Change…''' (or '''Connect…''').
* '''Reconnect automatically''' reconnects after the connection drops.
* '''Account''' shows whether you are signed in, with '''Sign out''' or '''Sign in…'''.

== Push-to-talk ==
'''Mode''' is '''Toggle''' or '''Hold to talk'''. '''Key''' and '''Mouse button''' bind the push-to-talk control: press '''Bind''', then the key or button. '''Clear''' removes a binding. See [[SimTX Guide/Transmitting#Push-to-talk|Transmitting]].

== Discord ==
'''Show activity in Discord''' shows what you are doing in your Discord status. '''Text''' sets the lines shown '''While transmitting''' and '''While idle''', with tokens such as <code>{callsign}</code> and <code>{freq_mhz}</code>; '''Format tokens''' lists them all. '''Images''' sets the image keys. Press '''Save''' to keep your changes.

== Extensions and Developer ==
'''Extensions''' manages installed audio add-ons and actions; '''Developer''' holds your own packages. See [[SimTX Guide/Catalog and add-ons|Catalog and add-ons]].

== Command palette ==
[[File:SimTX Guide Settings command palette.png|thumb|center|600px|alt=Command palette with the query antenna and results such as Transmit antenna, Aim the transmit antenna on the map and Track satellite, with key hints along the bottom.|The command palette searching for antenna.]]
The command palette runs any command in the app by name.
# Press Ctrl+K (⌘K on macOS).
# Type part of a command, for example ''antenna'' or ''coverage''.
# Use the arrow keys to choose and Enter to run.

Some commands open a list or ask for a value; Backspace goes back. Typing a frequency such as <code>14.230</code> or a power such as <code>100 W</code> offers to set it. Esc closes the palette.

== Keyboard shortcuts ==
{| class="wikitable"
! Action !! Windows and Linux !! macOS
|-
| Command palette || Ctrl+K || ⌘K
|-
| Start TX or RX (the visible tab) || Ctrl+Enter || ⌘↵
|-
| Set TX frequency || Ctrl+Shift+F || ⌘⇧F
|-
| Set TX power || Ctrl+Shift+W || ⌘⇧W
|-
| Set modulation || Ctrl+Shift+M || ⌘⇧M
|-
| Listen to own TX || Ctrl+Shift+L || ⌘⇧L
|-
| Run an action || Ctrl+Shift+A || ⌘⇧A
|-
| New station || Ctrl+Shift+T || ⌘⇧T
|-
| Transmit tab || Ctrl+1 || ⌘1
|-
| Receive tab || Ctrl+2 || ⌘2
|-
| Stations tab || Ctrl+3 || ⌘3
|-
| Catalog tab || Ctrl+4 || ⌘4
|-
| Health tab || Ctrl+5 || ⌘5
|-
| Settings || Ctrl+, || ⌘,
|}

[[Category:SimTX Guide]]

SimTX Guide/Health

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{{SimTX Guide navigation}}
The '''Health''' tab shows the load and state of the server you are connected to.

== The header ==
The header shows the server's name, when the report was last updated, and a status: '''Healthy''', '''Attention''' or '''Degraded'''. '''Auto-refresh''' updates the report every 5 seconds; '''Refresh''' updates it now.

Problems show as warnings below the header:
* ''The server is not accepting new connections.''
* ''System CPU at'' a percentage of 90 or more.
* ''Server memory is nearly full.''

== Overview ==
[[File:SimTX Guide Health.png|thumb|center|800px|alt=Server health for SimTX Demo marked Healthy, with uptime, clients, transmitters, receiver groups and sim time, CPU and heap bars, work queues, and tables of six transmitters and four receivers.|The Health tab for a healthy server, with its overview, resources, work queues and live sessions.]]
{| class="wikitable"
! Figure !! Meaning
|-
| '''Uptime''' || How long the server has been running.
|-
| '''Clients''' || Connected programs, with the number of stations in use.
|-
| '''Transmitters''' || Transmissions on the air.
|-
| '''Receiver groups''' || Groups of receivers that share processing.
|-
| '''Sim time''' || The simulation clock, in UTC.
|}

== Resources and work queues ==
'''Resources''' shows the server's CPU, the machine's CPU, memory, threads, open files and load average. '''Work queues''' shows how many session tasks, receiver DSP jobs and propagation jobs are running and waiting. Waiting jobs, overruns and '''Stalls''' above zero mean the server is falling behind.

== Transmitters and receivers ==
{| class="wikitable"
! Table !! Columns
|-
| '''Transmitters''' || '''Callsign''', '''Frequency''', '''Mode''', '''Rate''', '''Buffer''' (audio waiting at the server), '''Last data''' and '''Connected'''.
|-
| '''Receivers''' || '''Callsign''', '''Center''', '''Rate''', '''Queue''', '''Dropped''', '''Group''' and '''Connected'''.
|}

A short '''Buffer''' or a '''Last data''' time of a second or more means that transmitter's audio is not arriving fast enough. A full '''Queue''' or rising '''Dropped''' count means that receiver isn't reading its samples fast enough.

[[Category:SimTX Guide]]

SimTX Guide/Catalog and add-ons

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{{SimTX Guide navigation}}
The '''Catalog''' tab lists the extensions and presets that SimTX users share on the server. Extensions written in Lua add modulations, audio add-ons, actions, themes and libraries to the app.

== Browse the catalog ==
[[File:SimTX Guide Catalog browse.png|thumb|center|800px|alt=Catalog tab with search, the All, Extensions and Presets filters, the Newest sort, a list of entries, and CW Beacon selected with Install, author DEMO2, version, revision, size, package ID, and the contents of init.lua.|The Catalog with a modulation selected, showing its details and its init.lua.]]
* Search by name, author or tag.
* Filter by '''All''', '''Extensions''' or '''Presets''', and sort by '''Newest''', '''Name''', '''Author''' or '''Largest'''.
* A tick marks what you have installed; '''Update''' marks an installed entry with a newer revision.

Select an entry to see its author, version, revision, size, package ID and requirements. '''Preview''' shows a preset's settings or a theme. '''Files''' lists its files; manifests can be shown as a '''Table''' or as '''Source'''.

== Install an extension ==
# Select the extension.
# Press '''Install''', or '''Update''' when a newer revision is available.

[[Lua extensions]] describes how installed extensions appear in the app.

== Use a preset ==
* '''Apply to Transmit''' or '''Apply to Receive''' loads the preset's settings.
* '''Save to my presets''' adds it to the '''Presets''' menu.

== Publish an extension ==
# Press '''Publish…'''.
# Press '''Choose folder…''' and choose the extension's folder.
# Enter a '''Name''', a one-line '''Description''' and up to 12 '''Tags''', separated by commas.
# Press '''Publish'''.

If the server refuses the upload, the dialog shows why and stays open. Publishing needs a sign-in with permission to publish. To take your entry down, select it and press '''Remove publication…'''.

== Audio add-ons ==
Audio add-ons process your transmit audio before it is sent.
# Press '''Add-ons''' in the status bar at the bottom of the window.
# Switch each add-on on or off, drag rows to change the order, and open an add-on's options with its options button.

The order applies the next time you press '''Start TX'''. '''Manage extensions…''' opens '''Settings''', '''Extensions'''.

== Actions ==
Actions are tools added by extensions.
# Press '''Actions''' in the status bar, or open the command palette (Ctrl+K or ⌘K) and type the action's name.
# Press '''Run''', or '''Run…''' for an action with settings, adjust them and press '''Run'''.

Ctrl+Shift+A (⌘⇧A) also runs an action.

== Manage extensions ==
'''Settings''', '''Extensions''' lists installed audio add-ons and actions.
* '''Reload''' loads changed extensions again.
* '''Open folder''' opens the extensions folder.
* '''Install examples''' installs the example extensions.

Problems loading an extension show at the top of this section.

== Write a package ==
[[File:SimTX Guide Catalog package editor.png|thumb|center|800px|alt=New package form with Name Band Notes, Version 1.0.0, ID org.example.bandnotes, Entry file init.lua, a description, Types with Action selected, a dependency on example.shared-math with Compatible (^) 1.0.0, and Create package.|A new package in Settings, Developer, with its details and one dependency.]]
'''Settings''', '''Developer''' is a workspace for your own packages.
# Press '''New package…'''.
# Under '''Details''', enter the '''Name''', '''Version''', '''ID''' (like <code>com.example.mypack</code>), '''Entry file''' and '''Description''', and choose the '''Types'''.
# Add '''Dependencies''' with a version rule: '''Compatible (^)''', '''Patch updates (~)''', '''At least (>=)''', '''Exactly''' or '''Any version'''. Library packages also list '''Exports'''.
# Press '''Create package'''.
# Add and edit files in the file list. '''Save''' writes a file; '''Revert''' drops your changes.
# In '''Settings''', '''Extensions''', press '''Reload''' to try it.

'''Local packages''' lists your packages with '''Edit''' and '''Delete…'''. [[Creating Lua extensions]] explains how to write one, and [[Lua extension manifest]] describes the details fields.

[[Category:SimTX Guide]]

SimTX Guide/Map and coverage

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{{SimTX Guide navigation}}
The '''Stations''' tab shows a globe with the stations and satellites on the server, and a station list beside it.

== Station lists ==
[[File:SimTX Guide Map World list.png|thumb|center|389px|alt=World list with a search field, the filters All, Ground, Satellites and On air, four public stations such as Demo harbour club on 14.2650 MHz USB, and ad-hoc sessions such as DEMO10 on 5.3570 MHz FT8.|The World list with public stations and ad-hoc sessions, each showing what it is running.]]
{| class="wikitable"
! List !! Shows
|-
| '''Mine''' || Your ground stations and satellites, with '''New station''' and '''Launch satellite'''.
|-
| '''World''' || '''Public stations''', '''Ad-hoc''' sessions and satellites '''In orbit'''.
|}

In '''World''', search by callsign, owner or frequency, and filter by '''All''', '''Ground''', '''Satellites''' or '''On air'''. Each row shows what is running, for example ''2 on air'' or ''RX'', and for satellites the next pass. Select a row or a marker to open the station's details; '''Show on globe''' moves the globe to it.

== The globe ==
Drag to turn the globe and scroll to zoom.
{| class="wikitable"
! Marker or line !! Meaning
|-
| '''Your station''' || One of your stations.
|-
| '''On air''' || A station with a transmission running.
|-
| '''Listening''' || A station with a receiver running.
|-
| '''Satellite''' || A satellite at its current position.
|-
| '''New satellite''' || The satellite you are designing.
|-
| '''Your RX''' || Your ad-hoc receive location.
|-
| Dashed line from a station || A satellite above that station's horizon.
|-
| Line along a heading || A rotator antenna's heading; see [[SimTX Guide/Rotators and tracking#The beam line|Rotators and tracking]].
|}

The legend in the lower left also shows the simulation time in UTC. Day and night shading follows that clock. Selecting a satellite draws its ground track.

{| class="wikitable"
! Button !! What it does
|-
| '''Refresh''' || Reloads the station list.
|-
| '''Coverage''' || Shows the coverage of your Transmit station (see below).
|-
| '''Orbits''' || Shows or hides the orbit rings of all satellites.
|-
| Fit button || Zooms out to show all stations.
|}

== Coverage maps ==
[[File:SimTX Guide Map coverage.webp|thumb|center|800px|alt=Stations tab with green coverage shading on the globe, a Coverage legend reading Demo hilltop, Roof Yagi at 300°, 14.225 MHz, 100 W with an S1 to S9 scale, and the Coverage map panel with From, Antenna, Heading, Frequency, Power and Update.|A coverage map for the Yagi at Demo hilltop, with the coverage panel and the signal strength legend.]]
A coverage map shades the parts of the world where your Transmit station can be heard right now. Brighter shading means a stronger signal.
# In the '''Transmit''' tab, choose a ground station under '''Transmit from''' and set the frequency, power and mode.
# In the '''Stations''' tab, press '''Coverage'''. The button reads '''Computing…''' until the map arrives.
# Press '''Hide coverage''' to remove it.

The map uses the station's location and antenna, the rotator heading, the power up to the radio's cap, the frequency, mode and bandwidth, and the current propagation conditions. It is approximate. After changing any of these, press '''Hide coverage''' and '''Coverage''' again. Coverage maps work for ground stations only.

== Passes and satellites ==
Pass predictions are in a satellite's details; see [[SimTX Guide/Satellites#Passes|Satellites]].

== Map quality ==
[[File:SimTX Guide Map quality.png|thumb|center|800px|alt=Settings rows Theme set to Dark and Map quality set to Auto, with the note Auto uses Full on this computer.|The Map quality setting in Settings, General.]]
'''Settings''', '''General''', '''Map quality''' sets how much the globe draws.
{| class="wikitable"
! Setting !! Globe
|-
| '''Auto''' || Chooses Full or Light for this computer.
|-
| '''Full''' || Atmosphere, terrain, sharp detail and smooth camera flights.
|-
| '''Light''' || A simpler globe that stays smooth on slow computers.
|}

[[Category:SimTX Guide]]

SimTX Guide/Rotators and tracking

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{{SimTX Guide navigation}}
A '''rotator''' turns an antenna on a ground station. '''Tracking''' follows a satellite with the rotator and corrects its Doppler shift.

== Mounts ==
Set the '''Mount''' of each antenna in the station editor.
{| class="wikitable"
! Mount !! Turns !! Rate
|-
| '''Fixed''' || Not at all ||
|-
| '''Azimuth rotator''' || Around the horizon || 3° per second
|-
| '''Az-El rotator''' || Around the horizon and up to the zenith || 6° per second in azimuth, 4° per second in elevation
|}

'''Parks at azimuth''' (and '''Elevation''' on an Az-El rotator) is the stored heading, where the antenna points when a session starts.

== Turn an antenna by hand ==
[[File:SimTX Guide Rotators aim on map.png|thumb|center|660px|alt=Globe over Europe with an Aim Roof Yagi card reading 32°, 2,657 km with Cancel and Done, the current heading line labelled 300°, and a dashed line from Demo hilltop toward the northeast.|Aim on map: a dashed line runs from the station to the pointer, and the card shows its heading and distance.]]
[[File:SimTX Guide Rotators by hand.png|thumb|center|606px|alt=Rotator control with a compass dial, Azimuth 220, the Aim on map and Use stored heading links, and the line Turning to 220°, about 25 s.|The Rotator dial turning a beam antenna by hand to 220°.]]
The '''Rotator''' control is in the '''Station''' section of the '''Transmit''' and '''Receive''' tabs when the antenna has a rotator.
* Drag the dial, or type the '''Azimuth''' and, on an Az-El rotator, the '''Elevation'''. The arrow keys turn the dial 1°, Shift and an arrow 10°.
* '''Aim on map''': the app switches to the '''Stations''' tab. Click the globe or a station; the antenna points toward it, level with the horizon. Press '''Done''' to keep it.
* '''Use stored heading''' turns back to the stored heading.

On the dial, the needle is where the antenna points and the dot on the rim is the stored heading. The line below says what the rotator is doing, for example ''Turning to 285°, about 40 s.''

Off the air, the heading is where the next session starts. On the air, the rotator turns at once. The stored heading only changes in the station editor.

== Follow a satellite ==
[[File:SimTX Guide Rotators follow.png|thumb|center|606px|alt=Track a satellite set to AstroLink, Correct Doppler ticked, In view now, sets 13:32 UTC, and the Rotator switched from By hand to Follow AstroLink, with the satellite's azimuth and elevation.|The rotator following AstroLink, with Correct Doppler ticked.]]
# Under '''Track a satellite''', choose the satellite.
# The '''Rotator''' control switches to '''Follow''' and the satellite's name. '''Correct Doppler''' is ticked.

The antenna follows the satellite while it is above the horizon and waits where it will rise. '''By hand''' stops following. Choose '''Off''' under '''Track a satellite''' to stop tracking. On a '''Fixed''' antenna, tracking only corrects Doppler.

== How the rotator moves ==
* Each axis turns at its own rate, so a turn takes as long as the slower axis needs. A half turn on an azimuth rotator takes a minute.
* The stop is at north: azimuth runs from 0° to 360° and never crosses north, so 350° to 10° goes the long way round.
* A fast satellite passing overhead can outrun the rotator for a while near its highest point.

== The beam line ==
[[File:SimTX Guide Rotators beam line.webp|thumb|center|800px|alt=Globe of Europe and North Africa with an orange line from Demo hilltop labelled TX 300°, a blue line labelled RX 180°, 25° up, and dashed lines to satellites in view.|Beam lines from Demo hilltop: TX at 300° and RX at 180°, 25° up.]]
The globe in the '''Stations''' tab draws a line from the station along each rotator antenna's heading, with the heading as its label. It moves as the rotator turns. While you aim on the map, a dashed line runs from the station to the pointer.

== The heading on every band ==
The heading counts for HF skywave and ground wave, VHF and UHF paths, satellite links and the noise the antenna picks up. A beam pointed away from the other station can be weaker than a wire antenna.

[[Category:SimTX Guide]]

SimTX Guide/Satellites

2026-10-24T20:48:33Z

Clanker: Add screenshots of the SimTX desktop app

{{SimTX Guide navigation}}
A '''satellite''' is a station in orbit that you design and launch. It has antennas and radios like a ground station. At launch it is '''sealed''': its orbit, antennas, radios and attitude can't be changed, only its name, callsign and visibility. To change anything else, deorbit it and launch a new one.

== Launch a satellite ==
# In the '''Stations''' tab, select '''Mine''' and press '''Launch satellite'''. The globe shows the orbit as you design it.
# '''Orbit''': choose a preset and adjust it (see below). Press '''Next: Payload'''.
# '''Payload''': set the antennas, radios, attitude, name, callsign and visibility. Press '''Next: Launch'''.
# '''Launch''': check the summary, tick '''Sealed after launch''' and press '''Launch satellite'''.

The new satellite's details open after the launch.

=== Orbit presets ===
[[File:SimTX Guide Satellites orbit step.webp|thumb|center|800px|alt=Launch a satellite, Orbit step: preset cards Space station, Sun-synchronous, Geostationary and Custom, the More orbits link, altitude and inclination sliders at 420 km and 51.6°, the starting point, and orbit time, speed, footprint radius and max Doppler; the globe shows the new orbit.|The Orbit step of Launch a satellite with the Space station preset, and the planned orbit on the globe.]]
{| class="wikitable"
! Preset !! Orbit
|-
| '''Space station''' || Low orbit at 420 km and 51.6° that passes over most of the world.
|-
| '''Sun-synchronous''' || Crosses each place at the same local time every day.
|-
| '''Geostationary''' || Stays over one longitude, about 35,800 km up.
|-
| '''Custom''' || Set altitude, shape and tilt yourself.
|-
| '''Polar''' || Passes over both poles and sees the whole Earth each day.
|-
| '''Equatorial''' || Stays over the tropics with frequent passes near the equator.
|-
| '''Molniya''' || Long, high loops that hang over high latitudes for hours.
|}

'''Polar''', '''Equatorial''' and '''Molniya''' are under '''More orbits'''. Editing a value that a preset fixes switches to '''Custom'''.

=== Orbit controls ===
{| class="wikitable"
! Control !! Meaning
|-
| '''Circular''', '''Elliptical''' || One altitude, or a '''Lowest point''' and '''Highest point''' with the highest point over the '''North''' or '''South'''.
|-
| '''Altitude''' || 200 to 40,000 km. Higher orbits are slower, see more of the Earth and stay in view longer, but the signal is weaker.
|-
| '''Inclination''' || The tilt against the equator: 0° stays over the equator, 90° crosses the poles, above 90° runs against the Earth's rotation. The track reaches north and south to the latitude of the inclination. Sun-synchronous sets it for you.
|-
| '''Parked over longitude''' || Geostationary: where the satellite stays. From a given place it is always in view or never.
|-
| '''Highest point over longitude''' || Molniya: where its high point hangs.
|-
| '''Starting point''' || Where the first orbit begins, '''Northbound''' or '''Southbound'''. '''Pick on globe''' or '''Over my station…''' places it.
|-
| '''Orbital elements''' || The orbit as numbers, for typing exact values. '''Back to guided controls''' returns to the controls.
|}

Beside the form, '''Orbit takes''', '''Speed''', '''Footprint radius''', '''Max Doppler''', '''Coverage''' and the passes per day over each of your ground stations update as you design. A warning appears if the orbit can't be flown.

=== Payload ===
[[File:SimTX Guide Satellites payload step.png|thumb|center|777px|alt=Payload step with a Turnstile antenna, a 5 W radio with a link check of -105 dBm, the attitude options Earth-pointing, Spinning and Fixed in space, a Yaw field, and Back and Next: Launch buttons.|The Payload step with one antenna, one radio with its link check, and the attitude choices.]]
{| class="wikitable"
! Section !! Contents
|-
| '''Antennas''' || One to four antennas, fixed to the body. '''Rotation on the body''' turns an antenna on the body.
|-
| '''Radios''' || Up to eight radios, each with a '''Power cap'''. Small satellites run 1 to 10 W. '''Link check''' estimates the signal at a ground station at 30° elevation on 437.8 MHz.
|-
| '''Attitude''' || '''Earth-pointing''' keeps one face down, with a '''Yaw''' angle. '''Spinning''' spins at a '''Spin rate''' around an axis chosen under '''Spins around'''. '''Fixed in space''' holds one direction among the stars.
|-
| '''Name and visibility''' || '''Name''', '''Callsign''', and '''Public''' or '''Unlisted'''. An unlisted satellite can only be used by you, but others still hear it transmit.
|}

== Satellite details ==
Select a satellite in the '''Stations''' tab.
* '''Right now''': altitude, speed, the point below it, footprint radius and orbit time.
* '''On this station''': sessions running on it.
* '''Passes''' and '''Doppler now'''.
* '''Edit''' changes the name, callsign and visibility.

== Passes ==
[[File:SimTX Guide Satellites passes.png|thumb|center|380px|alt=Passes panel seen from Demo hilltop listing six passes with time, highest elevation and direction; the 46° pass is selected, with its sky plot and its rise, highest, set, duration and Doppler figures.|Passes of Nightjar-1 over Demo hilltop, with the sky plot of the selected pass.]]
A '''pass''' runs from AOS, when the satellite rises above your horizon, to LOS, when it sets. Its '''elevation''' is its height above the horizon, from 0° to 90° overhead. High passes are longer and stronger than low ones.

# Select the satellite in the '''Stations''' tab.
# Under '''Passes''', choose one of your ground stations in '''Seen from'''.
# Select a pass in the list to see its sky plot and when it '''Rises''', is '''Highest''' and '''Sets''', how long it '''Lasts''' and its '''Doppler''' range.

For a geostationary satellite the panel says whether it is always in view and where to point. Times are UTC simulation time, as in the map legend.

The next pass also shows in the '''Mine''' list, under '''Satellites over this station''' in a ground station's details, and under '''Track a satellite''' in the Transmit and Receive tabs.

Hills and mountains around a station can hide a satellite that is low in the sky, so the start and end of a pass, or a whole low pass, may be silent.

== Doppler ==
A satellite's signal arrives higher in frequency while it comes toward you and lower while it moves away, by several kilohertz on 70 cm. '''Doppler now''' in the satellite's details shows the shift for a frequency you enter.

To correct it:
# In the '''Transmit''' or '''Receive''' tab, choose a satellite under '''Track a satellite'''.
# Leave '''Correct Doppler''' ticked.

On receive, the tuning follows the shift. On transmit, the signal is shifted so it arrives on frequency at the satellite.

== Transmit from or receive at a satellite ==
Choose the satellite in '''Transmit from''' or '''Receive at'''.
* Transmitting from it sends a downlink from the satellite's position in orbit.
* Receiving at it hears the uplink, the signals that reach the satellite.

The tracking control is then '''Doppler-correct toward''' one of your ground stations: transmissions arrive on frequency there, and signals from there are received on frequency.

== Deorbit ==
[[File:SimTX Guide Satellites deorbit.webp|thumb|center|800px|alt=Satellite details with a Deorbit Nightjar-1 card: reentry in 29 min over 79.0° N, 100.4° E, a 179 m/s retrograde burn, one session ending at reentry, Cancel and Fire deorbit burn; the globe shows a red dashed path to a Reentry 05:59 UTC marker.|The deorbit confirmation for Nightjar-1, with the falling path and the reentry point on the globe.]]
A deorbit is a retrograde burn that brings the satellite down.
# In the satellite's details, press '''Deorbit…'''. The globe shows where it will fall.
# Check when and where it reenters, the burn and the sessions that will end.
# Press '''Fire deorbit burn'''. The burn can't be undone.

The satellite is then '''Deorbiting'''. It keeps working until it reaches 80 km and burns up; the '''Reentry''' panel counts down to that moment. Its sessions then end and it leaves the map.

[[Category:SimTX Guide]]

SimTX Guide/Stations

2026-10-24T20:48:32Z

Clanker: Add screenshots of the SimTX desktop app

{{SimTX Guide navigation}}
A '''station''' is the place you transmit and receive from. It is saved to your account and works on every server. A ground station has a name, a callsign, a location, one to eight antennas and up to eight radios. Several transmissions and receivers can use one station at the same time. Satellites are stations in orbit; see [[SimTX Guide/Satellites|Satellites]].

You manage stations in the '''Stations''' tab. '''Mine''' lists your ground stations and satellites; select one to see its details. [[SimTX Guide/Map and coverage|Map and coverage]] describes the globe and the lists.

== Create a station ==
[[File:SimTX Guide Stations pick on globe.webp|thumb|center|770px|alt=Globe over central Europe with a Place the station card showing 48.1990° N, 15.8554° E with Cancel and Done, and a new pin east of Demo hilltop.|Pick on globe: the new station's pin, its coordinates and the Done button.]]
# In the '''Stations''' tab, select '''Mine''' and press '''New station'''. The station editor opens with the sections '''Basics''', '''Location''', '''Antennas''' and '''Radios'''.
# Under '''Basics''', enter a '''Name''' and your '''Callsign''', and choose '''Public''' or '''Unlisted'''.
# Under '''Location''', press '''Pick on globe''', click the globe where the station stands and press '''Done'''. You can also drag the pin or type the '''Latitude''' and '''Longitude'''.
# Under '''Antennas''', set up the dipole the station starts with, or choose another type.
# Under '''Radios''', check the radio the station starts with.
# Press '''Create station'''.

=== Altitude ===
When you place the station, the app fills in '''Altitude''' with the ground height at that spot, in metres above sea level. If you type your own altitude, the app keeps it; '''Use ground height''' goes back to the ground height. If the lookup fails, enter the altitude by hand. Antenna height is set on each antenna.

== Antennas ==
[[File:SimTX Guide Stations antenna mount.png|thumb|center|663px|alt=Antenna card for Sat X-Yagi with type Crossed Yagi, driven element length, height, feedline loss, Mount set to Az-El rotator, Parks at azimuth 180, Elevation 25, and an SWR check at 435 MHz.|A crossed Yagi on an Az-El rotator that parks at 180° azimuth and 25° elevation.]]
[[File:SimTX Guide Stations antenna gallery.png|thumb|center|663px|alt=Add an antenna panel with cards for Dipole, Inverted-V, Vertical, Full-wave loop, Longwire, Beverage, EFHW 49:1, Yagi 3-el, Yagi 5-el, Crossed Yagi, Helix, Monopole, Turnstile and NEC deck.|The antenna gallery, grouped as Wire, Beam, Whip and turnstile, and Your own model.]]
'''Add antenna''' opens the antenna gallery, grouped as '''Wire''', '''Beam''' and '''Whip and turnstile'''. '''NEC deck''' under '''Your own model''' imports a wire model; see [[NEC File Import]].

{| class="wikitable"
! Field !! Meaning
|-
| '''Name''' || The name shown in the Transmit and Receive tabs.
|-
| '''Type''' || The antenna type. Changing it resets the length.
|-
| Length || The main dimension. Its label depends on the type.
|-
| '''Height''' || Height above the ground, in metres.
|-
| '''Feedline loss''' || Loss of the cable to the radio, in dB.
|-
| '''Mount''' || '''Fixed''', '''Azimuth rotator''' or '''Az-El rotator'''.
|-
| '''Points toward''' || On a '''Fixed''' mount, the direction of a directional antenna, in degrees from north.
|-
| '''Parks at azimuth''', '''Elevation''' || On a rotator, where the antenna points when a session starts. '''Elevation''' is only on an Az-El rotator.
|-
| '''Check SWR at''' || The antenna's SWR at a frequency you choose.
|}

'''Import NEC deck…''' replaces the built-in model with your own and '''Use built-in''' goes back. '''Remove''' deletes the antenna; a station keeps at least one. See [[Antenna System]] for choosing and tuning, and [[SimTX Guide/Rotators and tracking|Rotators and tracking]] for rotators.

== Radios ==
[[File:SimTX Guide Stations radios.png|thumb|center|698px|alt=Radios section with HF transceiver expanded: Based on, Name, Power cap 100 W with 5, 10, 100 and 400 W shortcuts, Noise figure 8 dB and Transmitter imperfections, followed by a second radio, Portable 10 W.|A radio opened in the station editor, with its power cap and noise figure.]]
A '''radio''' is a saved transmitter and receiver profile. '''Add radio''' adds one; '''Based on''' fills in typical values for a radio model.
{| class="wikitable"
! Field !! Meaning
|-
| '''Name''' || The name shown in the Transmit and Receive tabs.
|-
| '''Power cap''' || The most power a transmission on this radio can use, in watts.
|-
| '''Noise figure''' || The receiver noise figure, in dB.
|-
| '''Transmitter imperfections''' || How the transmitter sounds. See [[Advanced Transmitter Settings]].
|}

* The first radio is the station's default. The Transmit and Receive tabs show it as ''<name> (default)''.
* A transmission can't exceed the power cap or your account's power limit, whichever is lower.
* Without a radio, sessions use a generic HF transceiver and your account's power limit.

== Public and unlisted ==
{| class="wikitable"
! Visibility !! Meaning
|-
| '''Public''' || Shown on the map, and anyone signed in can receive from it.
|-
| '''Unlisted''' || Hidden from the map and usable only by you.
|}

Only you can transmit through your stations.

== Transmit and receive ==
* '''Transmit from here''' in a station's details opens the '''Transmit''' tab with the station chosen. See [[SimTX Guide/Transmitting|Transmitting]].
* '''Receive here''' opens the '''Receive''' tab with the station chosen. It also works on other people's public stations. See [[SimTX Guide/Receiving|Receiving]].

== Edit a station ==
[[File:SimTX Guide Stations editor.webp|thumb|center|800px|alt=Edit Demo hilltop: a globe of central Europe with the station pin, and the editor with Name, Callsign, Public or Unlisted, the location 47.27° N, 11.39° E at 574 m, three antennas, two radios, Cancel and Save.|The station editor for Demo hilltop, with the globe on the left and the Basics, Location, Antennas and Radios sections on the right.]]
# Select the station under '''Mine''' and press '''Edit''', or press '''Edit station''' in the Transmit or Receive tab.
# Make your changes and press '''Save'''.

Running sessions switch to the new settings without reconnecting. A session on an antenna or radio you remove ends; the editor warns before you save.

== Delete a station ==
# In the station's details or the editor, press '''Delete…'''.
# Confirm with '''Delete station'''.

The station, its antennas and radios are removed and its sessions end. This can't be undone.

== Use my previous setup ==
With no stations yet, '''Use my previous setup''' creates a station from the callsign, location, antenna and radio of your earlier transmit setup.

[[Category:SimTX Guide]]

SimTX Guide/Receiving

2026-10-24T20:48:32Z

Clanker: Add screenshots of the SimTX desktop app

{{SimTX Guide navigation}}
The '''Receive''' tab starts a receiver on the server and passes its signal to an SDR program on your computer through a '''bridge'''. The setup is on the left; the '''Bridges''' list is on the right.

== Receive a signal ==
[[File:SimTX Guide Receiving receive tab.png|thumb|center|800px|alt=Receive tab with My station selected, Receive at Demo hilltop, the Roof Yagi antenna and its rotator, center frequency 14.2 MHz, sample rate 250000, and a running bridge Hilltop 20 m on 127.0.0.1:1234.|The Receive tab receiving at Demo hilltop, with one bridge running.]]
# Under '''Where you listen''', choose where the receiver is.
# Under '''Tuning''', set the '''Center frequency''' and the '''Sample rate (Hz)'''.
# Press '''Start RX'''.
# In your SDR program, connect an rtl_tcp source to the address shown under '''Bridge''', by default <code>127.0.0.1:1234</code>.

[[How to receive]] shows the settings in SDR++, and [[Guide to setting up sdr console with simtx|the SDR Console guide]] in SDR Console.

== Where you listen ==
{| class="wikitable"
! Choice !! Receiver !! Needs
|-
| '''My station''' || One of your stations: choose it under '''Receive at''', with its '''Antenna''' and '''Radio'''. || Sign-in
|-
| '''Public station''' || Another account's public station. Search under '''Find a public station''' and select it. The session uses the station's main antenna. || Sign-in
|-
| '''Ad-hoc''' || Any location, with a '''Callsign''' and '''Antenna''' of your own. || Nothing
|}

For '''Ad-hoc''', type the '''Latitude''' and '''Longitude''' or press '''Pick location on map'''. '''Antenna details''' sets the antenna's length, '''Height (m)''', '''Azimuth (°)''' and '''Feedline loss (dB)'''.

'''Receive here''' in a station's details in the '''Stations''' tab chooses that station. On your own station, '''Track a satellite''' and the '''Rotator''' work as for transmitting; see [[SimTX Guide/Rotators and tracking|Rotators and tracking]].

== Tuning ==
{| class="wikitable"
! Field !! Meaning
|-
| '''Center frequency''' || The middle of the band you receive.
|-
| '''Sample rate (Hz)''' || The width of the band, in samples per second. 250,000 suits shortwave; FM broadcast needs about 1,024,000 or more.
|}

'''Tune RX''' next to a transmission in a station's details sets the center frequency to it.

== Bridge ==
{| class="wikitable"
! Field !! Meaning
|-
| '''Label''' || A name for the bridge in the '''Bridges''' list.
|-
| '''Listen address''' || Where your SDR program connects. <code>127.0.0.1</code> is this computer only. <code>0.0.0.0</code> lets other computers on your network connect, and anyone there can retune it.
|-
| '''rtl_tcp port''' || The port your SDR program connects to. Default 1234.
|-
| '''Hardware profile''' || The RTL-SDR model the bridge presents to your SDR program. Default Generic R820T.
|-
| '''Timestamped role''' || Adds a timestamp to each block of samples. Your SDR program gets the same samples.
|-
| '''Digital AGC''' || Starts the bridge with digital automatic gain control. On by default.
|}

== Link resilience ==
'''Smooth over network dropouts''' adds a jitter buffer, retries and concealment of short dropouts. It is on by default. '''Advanced tuning''' sets:
{| class="wikitable"
! Field !! Default
|-
| '''Read timeout (ms)''' || 5000
|-
| '''Max retries''' || 3, or -1 for no limit
|-
| '''Retry base delay (ms)''' || 250
|-
| '''Jitter buffer (ms)''' || 150, or -1 for off
|-
| '''Narrow upstream on repeated stalls''' || Lowers the sample rate when the link keeps stalling.
|}

== Bridges ==
[[File:SimTX Guide Receiving bridge.png|thumb|center|792px|alt=Bridges list with one bridge, Hilltop 20 m, Running, 14.2000 MHz, 250.00 kS/s, 127.0.0.1:1234, on Demo hilltop with the Roof Yagi, and a Stop button.|A running bridge in the Bridges list, with the address for the SDR program.]]
Each '''Start RX''' adds a bridge to the list, with its frequency, sample rate, address and state: '''Starting''', '''Running''', or ended. A line of link figures appears after trouble: reconnects, underruns, concealed blocks, narrowing and dropped blocks.
* '''Stop''' ends one bridge, '''Stop all''' every bridge after you confirm.
* '''Clear finished''' removes ended bridges.

== Presets ==
'''Presets''' at the top saves and loads complete receive setups, the same way as on the [[SimTX Guide/Transmitting#Presets|Transmit tab]].

[[Category:SimTX Guide]]

SimTX Guide/Transmitting

2026-10-24T20:48:31Z

Clanker: Add screenshots of the SimTX desktop app

{{SimTX Guide navigation}}
The '''Transmit''' tab puts a signal on the air from one of your stations. The setup is on the left; the '''Radio deck''' and the '''Sessions''' list are on the right.

== Transmit a signal ==
# Under '''Station''', choose the station in '''Transmit from''', then its '''Antenna''' and '''Radio'''.
# Under '''RF signal''', set '''Frequency''', '''Power (W)''' and '''Modulation'''.
# Under '''Source''', choose what to send.
# Press '''Start TX'''.

If something is missing, a message beside '''Start TX''' says what, with a button that fixes it. See [[SimTX Guide/Troubleshooting#Before Start TX|Troubleshooting]].

== Station ==
[[File:SimTX Guide Transmitting station.png|thumb|center|636px|alt=Station section with Transmit from Demo hilltop, Antenna Roof Yagi, Radio HF transceiver, Track a satellite Off, a rotator dial at 300 degrees with Aim on map, and an SWR graph around 14.225 MHz.|The Station section with a rotator antenna chosen, showing the Rotator dial and the SWR around the frequency.]]
{| class="wikitable"
! Control !! What it does
|-
| '''Transmit from''' || The station the transmission runs from. It sets your callsign and location. '''Create a station''' appears if you have none.
|-
| '''Antenna''', '''Radio''' || The station's antenna and radio to use. The first radio is the default.
|-
| '''Edit station''' || Opens the station editor.
|-
| '''Track a satellite''' || Corrects Doppler for a satellite, and points a rotator at it. See [[SimTX Guide/Rotators and tracking|Rotators and tracking]].
|-
| '''Rotator''' || Turns an antenna on a rotator. Shown only for rotator antennas.
|-
| '''SWR around your frequency''' || The antenna's SWR near the transmit frequency.
|}

[[SimTX Guide/Stations|Stations]] covers creating stations, antennas and radios.

== RF signal ==
{| class="wikitable"
! Control !! What it does
|-
| '''Frequency''' || The carrier or dial frequency. The unit menu switches between Hz, kHz and MHz.
|-
| '''Power (W)''' || Transmitter power. The label shows ''up to'' the radio's power cap.
|-
| '''Modulation''' || The mode, for example AM, SSB, FM or a data mode. See [[Modulation Modes]].
|-
| '''Bandwidth (Hz)''' || The transmitted bandwidth. '''Auto''' uses the usual bandwidth of the mode.
|-
| '''Low-cut (Hz)''' || Removes audio below this frequency.
|-
| '''WFM input''' || For wide FM: '''MPX composite (channel 1)''', which needs a source at 192 kHz or more, or '''Mono baseband''' with a '''Pre-emphasis''' of none, 50 µs or 75 µs.
|-
| '''Transmitter imperfections''' || Final drive, compressor, frequency error and AM index for this transmission. They start from the radio's values. See [[Advanced Transmitter Settings]].
|}

The line ''Wire rate'' shows the audio sample rate sent to the server. Modes from an extension show their own controls here.

== Source ==
[[File:SimTX Guide Transmitting source.png|thumb|center|636px|alt=Source section with the menu open, listing Audio file, Input device, White noise, PipeWire and GNU Radio IQ.|The Source menu with the five source types.]]
{| class="wikitable"
! Source !! Sends !! Settings
|-
| '''Audio file''' || An audio file or stream. || '''File or URL''', '''Choose…''', '''Loop playback'''
|-
| '''Input device''' || A microphone or other audio input. || '''Input device''', '''Capture rate (Hz)'''
|-
| '''White noise''' || A test signal generated by the server. || '''Tone (Hz)'''
|-
| '''PipeWire''' || Audio from the PipeWire graph on Linux. || '''Capture rate (Hz)'''
|-
| '''GNU Radio IQ''' || Complex baseband from GNU Radio, for modulation '''IQ'''. || '''IQ port (127.0.0.1)'''; set the GNU Radio sink to the rate shown.
|}

'''Audio gain''' sets the level of the source. [[Transmission Sources]] has more on each source.

== Presets ==
'''Presets''' at the top saves and loads complete transmit setups.
* To save, type a '''Preset name''' and press '''Save'''. A preset with the same name is replaced after you confirm.
* To load, choose a saved preset from the list.
* '''Load from file…''' and '''Save to file…''' use a preset file anywhere on disk. '''Open presets folder''' shows where saved presets are kept.

Presets from other users are in the '''Catalog''' tab; see [[SimTX Guide/Catalog and add-ons|Catalog and add-ons]].

== Radio deck ==
[[File:SimTX Guide Transmitting adjust on air.png|thumb|center|792px|alt=Radio deck with Adjust while on air expanded, showing Frequency, Power, Bandwidth, Final drive, PA headroom, Compressor and Audio gain fields.|Adjust while on air, opened under the Radio deck meters.]]
[[File:SimTX Guide Transmitting radio deck.png|thumb|center|792px|alt=Radio deck for DEMO1 USB on 14.2250 MHz on Demo hilltop, with FWD, REF, SWR, ALC, TEMP and BUF meters, Adjust while on air, and Listen to own TX.|The Radio deck for a running USB session, with its meters and the Pause and Stop buttons.]]
Select a session in the '''Sessions''' list to show it in the radio deck.
{| class="wikitable"
! Meter !! Shows
|-
| '''FWD/W''' || Power leaving the transmitter.
|-
| '''REF/W''' || Power reflected by the antenna.
|-
| '''SWR/:1''' || How well the antenna matches. The higher it is, the less power reaches the antenna. See [[SWR and Transmitter Protection]].
|-
| '''ALC/dB''' || How much the level control is reducing the signal.
|-
| '''TEMP/C''' || Temperature of the final amplifier. See [[Power Amplifier Behaviour]].
|-
| '''BUF/s''' || Audio waiting at the server. Near zero, listeners hear gaps.
|-
| '''DEV/kHz''' || FM deviation, with a reference tick.
|-
| '''MOD/%''' || AM modulation depth.
|-
| '''DRV/%''' || IQ drive level.
|}

* '''Pause''' silences the session without ending it; '''Resume''' continues.
* '''Stop''' ends the session.
* '''Adjust while on air''' changes '''Frequency''', '''Power (W)''', '''Bandwidth (Hz)''', '''Final drive (dB)''', '''PA headroom (dB)''', '''Compressor (dB)''' and '''Audio gain''' without stopping. Type a value and press Enter.
* '''Listen to own TX''' plays your signal as transmitted, before propagation. '''Stop listening''' ends it.

== Sessions ==
[[File:SimTX Guide Transmitting sessions.png|thumb|center|791px|alt=Sessions list with Stop all and Clear finished, and four sessions: DEMO1 USB running, DEMO1 AM paused, DEMO1/P FT8 queued 2 of 3, and DEMO1 CW finished.|The Sessions list with a running, a paused, a queued and a finished session.]]
Each '''Start TX''' adds a session to the list, with its label, number, state and frequency. '''Stop all''' ends every session after you confirm. '''Clear finished''' removes ended sessions.

{| class="wikitable"
! State !! Meaning
|-
| '''Starting''' || Connecting to the server.
|-
| '''Queued''' || Every transmitter slot on the server is taken. It starts by itself when one is free.
|-
| '''Running''' || On the air.
|-
| '''Paused''' || On the air but silent.
|-
| '''Stopped''' || Ended by you.
|-
| '''Finished''' || The audio file ended.
|-
| '''Failed''' || Ended by an error. The message says why.
|-
| '''Kicked''' || Ended by the server, for example by a moderator, or because the station was deleted or its satellite reentered. The message gives the reason.
|}

== Push-to-talk ==
Push-to-talk pauses and resumes your transmission with a key or mouse button while the app window is in front.
# Open '''Settings''', '''Push-to-talk'''.
# Choose the '''Mode''': '''Toggle''' switches with each press, '''Hold to talk''' transmits while the button is held.
# Press '''Bind''' next to '''Key''' or '''Mouse button''', then press the key or click the button.

If nothing is on the air, pressing push-to-talk starts a session with the current setup.

== Keyboard ==
{| class="wikitable"
! Action !! Windows and Linux !! macOS
|-
| Start TX || Ctrl+Enter || ⌘↵
|-
| Set TX frequency || Ctrl+Shift+F || ⌘⇧F
|-
| Set TX power || Ctrl+Shift+W || ⌘⇧W
|-
| Set modulation || Ctrl+Shift+M || ⌘⇧M
|-
| Listen to own TX || Ctrl+Shift+L || ⌘⇧L
|}

In the command palette (Ctrl+K or ⌘K), typing a frequency such as <code>14.230</code> or a power such as <code>100 W</code> offers to set it. See [[SimTX Guide/Settings and shortcuts|Settings and shortcuts]].

[[Category:SimTX Guide]]

Getting Started

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Clanker: Add screenshots of the SimTX desktop app

{{Documentation navigation}}

This guide goes from installing the SimTX desktop app to a first transmission and listening to it. TX means transmit and RX means receive.

== 1. Install the app ==
Download the app from the [https://manifest.simtx.net SimTX downloads page]:
* '''Windows''': the 64-bit <code>.exe</code> installer.
* '''macOS''': the <code>.dmg</code> for Apple Silicon. The first time, right-click the app and choose '''Open''' to get past the macOS security warning.
* '''Linux''': <code>.deb</code>, <code>.rpm</code>, Arch or Void packages, or an AppImage. The [https://manifest.simtx.net/install install page] explains how to add the package repository. Ubuntu 24.04 or Debian 13 or newer is needed.

== 2. Sign in and connect ==
[[File:SimTX Guide Getting Started server.png|thumb|center|482px|alt=Connect to a server dialog showing Signed in at auth.simtx.net, the Server menu set to SimTX Demo, and the Work offline and Connect buttons.|The Connect to a server dialog after sign-in, with a server chosen.]]
# Open the app. In '''Sign in to SimTX''', press '''Sign in'''.
# Press '''Open browser''', sign in to your SimTX account and approve the device. '''Copy link''' copies the address instead.
# In '''Connect to a server''', choose a '''Server''' and press '''Connect'''.

The top right of the window then shows the server and '''Connected'''. '''Work offline''' opens the app without connecting.

== 3. Create your first station ==
[[File:SimTX Guide Getting Started first station.png|thumb|center|640px|alt=Top of the Transmit tab with the Station section outlined, a guide tag reading Create the station you transmit from, and a Create a station button.|The getting started guide outlines the Station section and points to Create a station.]]
A '''station''' holds your callsign, location, antennas and radios. On first start, the in-app '''getting started guide''' points at each control in turn.
# In the '''Transmit''' tab, press '''Create a station'''.
# Under '''Basics''', enter a '''Name''' and your '''Callsign'''.
# Under '''Location''', press '''Pick on globe''', click where the station stands and press '''Done'''.
# Under '''Antennas''', open the dipole and set the length to <code>31</code> m and the '''Height''' to <code>10</code> m. This suits the frequency below.
# Press '''Create station'''.

The station now shows under '''Transmit from'''. See [[SimTX Guide/Stations|Stations]].

== 4. Make a first transmission ==
[[File:SimTX Guide Getting Started transmit ready.png|thumb|center|800px|alt=Transmit tab with Demo hilltop as the station, an EFHW antenna, a 100 W radio, an SWR graph, frequency 4625 kHz, power 100 W, AM Double Sideband Full Carrier, and an empty Radio deck.|The Transmit tab set up for a first transmission on 4625 kHz in AM.]]
In the '''Transmit''' tab:
# Set '''Frequency''' to <code>4625</code> with the unit '''kHz''', and '''Power (W)''' to <code>100</code>.
# Choose the '''Modulation''' '''AM Double Sideband Full Carrier''' and tick '''Auto''' beside '''Bandwidth (Hz)'''.
# Under '''Source''', choose '''Audio file''', press '''Choose…''' and pick a short audio file.
# Press '''Start TX'''.

The session appears in the '''Sessions''' list as '''Running'''. '''Queued''' means every transmitter slot is taken; it starts by itself when one is free. Select the session to see the '''Radio deck''' meters. '''Listen to own TX''' plays your signal as transmitted. '''Stop''' ends it.

[[SimTX Guide/Transmitting|Transmitting]] covers every control. If the session fails, its message says why; see [[SimTX Guide/Troubleshooting|Troubleshooting]].

== 5. Receive ==
You need an SDR program that supports rtl_tcp, such as SDR++.
# Open the '''Receive''' tab. Under '''Where you listen''', choose '''My station''', '''Public station''', or '''Ad-hoc''' for any location without an account.
# Set the '''Center frequency''' to <code>4625</code> kHz and the '''Sample rate (Hz)''' to <code>250000</code>.
# Press '''Start RX'''.
# In your SDR program, connect an rtl_tcp source to <code>127.0.0.1:1234</code> and tune to 4625 kHz in AM.

[[How to receive]] shows the settings in SDR++, and [[SimTX Guide/Receiving|Receiving]] covers every receive control. [[Propagation Basics]] explains how distance, band and time of day change what a receiver hears.

== Continue from here ==
* [[SimTX Guide]]: all user guides.
* [[Transmission Sources]]: microphones, streams and other sources.
* [[Modulation Modes]]: choosing a mode.
* [[Antenna System]]: changing frequency and choosing an antenna.
* [[Lua extensions]]: extensions and themes.

[[Category:SimTX]]
[[Category:SimTX Guide]]

File:SimTX Transmitter desktop app.png

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