OscarWatch Terminal

Tools → OscarWatch Terminal lets you hold short typed contacts with other stations through a satellite that relays packet radio, such as the ISS on 145.825 MHz. You type a call and a message, OscarWatch turns it into tones, your radio sends it up, and the satellite repeats it back down for everyone in its footprint. Terminal shows everything heard, keeps track of who you are working and logs the contacts for you. Everything you need is built in: you do not need Direwolf or any other soundmodem application.

On this page

• How it works
• What you need
• First-time setup
• Your first pass
• The window
• Waterfall
• Macros
• Message formats
• Positions and map
• Logging
• UHM
• APRS-IS
• Modem settings explained
• Using Direwolf or UZ7HO
• KISS modems and TNCs
• Yaesu FT-847
• Problems
• Words used here

How it works

Packet radio sends text as short bursts of two audio tones, 1200 Hz and 2200 Hz, at 1200 bits a second. Each burst is called a frame and carries who it is from, who it is to and the message. A satellite with a digipeater listens for frames and sends a copy straight back down. If you hear your own frame come back, you know the satellite heard you.

On the ISS the uplink and downlink are the same frequency (145.825 MHz). That means you cannot listen while you transmit, so OscarWatch waits for a quiet moment, sends, then listens again. A typical contact is a CQ with your grid square, a reply with theirs, a signal report each way and a 73. Each frame takes about half a second, so a whole contact fits easily into a pass.

OscarWatch keeps tuning the radio for Doppler shift as usual while Terminal is open. Keep radio control (CAT) tracking running for the satellite you are working, so the radio stays on the right frequency through the pass.

What you need

• A 2 m FM radio connected to the PC for audio. A radio with a built-in USB sound interface (it shows in Windows as something like USB Audio CODEC) is easiest. A separate USB sound interface, such as a SignaLink or Digirig, works too.
• A way to key the transmitter: VOX in the radio or interface, radio control (CAT), or a serial control line on the interface. See Push to talk.
• Your callsign and grid square in Settings → Station in the main window.
• Radio control set up in OscarWatch, so the radio follows Doppler. See Radio & rotator.

First-time setup

Open Tools → OscarWatch Terminal, then the Settings button at the top right of the Terminal window. This opens OscarWatch Terminal settings, which has its own tabs separate from the main OscarWatch Settings.

1. Modem tab. Leave Callsign empty to use your station callsign, and leave SSID on 0, which is what most satellite operators use. Check Connection says Built-in soundmodem (1200 or 9600). This is the default. Set Modem rate to Automatic for most satellites, or choose 1200 baud AFSK or 9600 baud G3RUH. Under Push to talk, pick how OscarWatch keys the radio. See Push to talk if you are not sure.
2. Soundcard tab: choose the devices. Set Input (from the radio) and Output (to the radio) to your radio's sound interface. They usually have the same name, for example Microphone (USB Audio CODEC) and Speakers (USB Audio CODEC). For 9600 baud, use the radio's data port and a 48 kHz device if Windows offers one. Click Refresh if you plugged the radio in after opening the window.
3. Set the receive level. Tick Monitor input. Tune the radio to a busy packet frequency, or open the squelch so you hear noise, and aim for 30 to 70% on the meter. The text under the meter says whether the level is too low, good or clipping. Change the radio's data output level or the Windows recording level to adjust it.
4. Set the transmit level. Connect a dummy load, or pick a clear frequency. Choose a test tone and press Send. The radio transmits for 5 seconds. Adjust TX level so the radio's deviation is about 3 kHz. Without a deviation meter, listen on a second receiver: the tones should sound clean and about as loud as other packet stations, not distorted.
5. Save, then press Connect in the Terminal window if it has not connected on its own.

Push to talk (Modem tab)

• VOX / audio: the radio or interface keys itself when it hears audio from the PC. Simplest to set up. Many USB interfaces such as the SignaLink work this way.
• CAT: OscarWatch keys the radio through the same radio control connection it uses for Doppler. Good for radios with a USB lead that carries both control and audio.
• CAT port RTS/DTR: keys the radio with a control line on the radio control COM port.
• Separate COM port: keys the radio with a control line on another COM port, for interfaces such as the Digirig that have their own. Choose the port and the line (RTS or DTR), and tick Invert if your interface needs it. It may be the same port FT4 uses. Closing the Terminal window releases it.

For anything other than VOX you can also set PTT lead (ms), the pause between keying and sending audio, and PTT tail (ms), the pause after the audio before unkeying.

If OscarWatch closes unexpectedly while the radio is keyed over CAT, it sends the radio a receive command the next time it starts, and the Terminal window shows a notice so you can check the radio is no longer transmitting.

Your first pass

1. In the main window, focus the ISS (or another satellite with a packet digipeater) and make sure radio control is tracking it.
2. Open Tools → OscarWatch Terminal. The status bar at the bottom shows Modem: OscarWatch 1200 AFSK or OscarWatch 9600 G3RUH with the input level and how many frames have been decoded.
3. Before the satellite rises, a yellow notice says it is below the horizon. OscarWatch will not transmit while it is below the horizon, so nobody on the ground is bothered by frames that the satellite cannot hear.
4. Once the satellite is up, frames start to appear in the message log. Listen for a minute to get a feel for who is active.
5. Press F1 to call CQ with your grid square, or click a station under Heard stations to answer them, then use F2 to send a report and F3 or F4 to finish.
6. When both of you have exchanged grids or reports and a roger or 73, OscarWatch logs the contact on its own.

The window

Top left: sending

• Shortcuts: buttons for F1 to F8 send your macros. F12 Log QSO logs the station in the To box straight away.
• To and Message: type a callsign (or CQ) and some text, then press Enter or Send. Messages can be up to 67 characters.
• TX delay (s): waits this many seconds before sending. Handy on a busy pass, so your frame does not land on top of the station you are answering.
• Format: APRS or Plain text. See Message formats. Next to it, the last thing you sent.
• Send Position: sends your location as an APRS position. See Sending your position.
• At the very top: Connect or Disconnect, the globe button for the Terminal Map, and Settings.

Top right: Station and Waterfall

The Station tab shows your call and grid, the satellite, its elevation, azimuth and range, and the time to LOS (or AOS while it is below the horizon), with a bar showing how high the satellite is. Underneath are the pass statistics: unique callsigns heard, frames you sent and received, how many of yours came back through the digipeater, the median time they took, and how many UHM users are active. Reset clears the statistics and the QSO and Heard stations lists.

The Waterfall tab shows the receive audio. See Waterfall.

Message log

Every frame heard, newest at the bottom, with the time in UTC, who sent it, who it is to and the message. Hover over a row to see the raw frame, and double-click a row to put that station in the To box. The Type column names each kind of row, and the row colour matches, so you never have to rely on colour alone:

Type	Meaning
TO ME	A message addressed to you
CQ	Someone calling CQ
MY TX	A frame you sent
MY DIGI	Your own frame, heard back through the satellite
TLM	Telemetry (data from a satellite or station)
BEACON	An automatic beacon

On MY DIGI rows, Delay shows how long your frame took to come back through the satellite. Q shows how cleanly the built-in modem copied each frame, as a percentage. A high figure means a strong, clean signal; a low one means the frame only just made it, which helps you compare antennas or audio levels.

QSO and Heard stations

• QSO: the stations you are working, with how far each contact has got (for example Report sent or Complete), their UHM status and whether they are logged.
• Heard stations: everyone heard this session, with how long ago, how many CQs and frames, the satellite's elevation as seen from their grid, their distance from you, and whether they are a new callsign, a new grid or already worked. Click a station to put it in the To box.

Along the bottom

• Legend: the row colours used in the message log.
• Scroll to last line: keeps the newest frame in view.
• Show stations: shows or hides the QSO and Heard stations boxes, giving the message log more room.
• Only my traffic: shows only frames to or from you.
• Clear log: empties the message log.
• The status bar shows the modem, the message format and path, APRS-IS and UHM, and the UTC time.

Text size, columns and layout

The message log, QSO and Heard stations boxes each have A− and A+ buttons to change the text size; holding Ctrl and turning the mouse wheel over a box does the same. Drag the lines between column headings to change a column's width, and double-click one to put it back. You can also drag the gaps between the boxes. OscarWatch remembers all of this for next time.

Each box has its own Clear button. On the message log it removes the frames. On QSO it moves those stations back to Heard stations only. On Heard stations it removes everyone, which empties the QSO list too. None of these reset the statistics; use Reset on the Station tab for that.

Portable and mobile

Terminal uses your station location for your grid, the grid in macros and logged contacts, and the elevation and LOS figures. To follow a GPS, set it up in Settings → GPS and turn on Automatically update station position from GPS fix. A GPS or Saved label beside your grid shows which location is in use. When you cross into a new grid square, the status line tells you, so you can check any macro where you typed your grid by hand.

Waterfall

The Waterfall tab shows the audio coming from the radio, from 300 to 3,000 Hz left to right, with newer audio at the top. Dashed lines labelled 1200 and 2200 mark the two packet tones. A packet shows as a short bright block covering both lines. A steady line somewhere else is usually a carrier or interference.

On FM with the squelch open, the waterfall shows a fine speckle of background noise. That is normal. When a strong packet arrives, the noise drops away and the two tones stand out. The waterfall only works with the built-in soundmodem, because other soundmodem applications keep the audio to themselves.

Macros

The F1 to F8 buttons send macros, which you edit on the Macros tab of Terminal settings. These placeholders are filled in when you send:

• {CALL}: the callsign in the To box
• {MYCALL}: your callsign
• {MYGRID}: your full grid square; {MYGRID4}: its first four characters

The defaults are CQ {MYGRID4} (F1), {MYGRID4} 599 (F2), R73 (F3) and 73 TU (F4). Tick To CQ for a macro that should always go to CQ rather than the station in the To box. A macro whose text is just {POSITION} sends your position instead of a message. Restore default macros puts the defaults back.

Message formats

Each satellite has a message format and a digipeater path, which Terminal picks for you from the satellite you have focused. You rarely need to change them.

Satellite	Format	Path
ISS (25544)	APRS	ARISS
Other satellites with a packet digipeater	APRS	none

• APRS sends a CQ as an APRS status containing the message you typed (the F1 macro is >CQ IO85) and a message to a station as an APRS message addressed to them. This is what most stations on the ISS use, and it also shows up on aprs.fi when an internet gateway hears it.
• Plain text puts your text straight into the frame, with the To callsign as the destination.
• The path tells the satellite to repeat the frame. ARISS is the name the ISS digipeater answers to.

Use the Format buttons in the window to switch for this session, or the Satellites tab of Terminal settings to change a satellite's format, path, modem, link type or the name used for UHM. Modem is a list: 1200 AFSK and 9600 G3RUH use the built-in modem. BPSK and GMSK need UZ7HO or another external modem. Add focused satellite adds the satellite you are tracking to that list.

APRS positions and the Terminal Map

Many stations send APRS position reports. Terminal reads all the common kinds (plain, compressed and Mic-E) and fills in the station's grid, distance and bearing under Heard stations. A grid a station types in a message always wins over one worked out from its position. For Mic-E positions from mobile radios, the altitude and a status such as En route or Emergency are shown too.

The globe button (Terminal Map) opens a map of heard stations with a known location, with your station and the satellite's footprint, so you can see who is in range now. Hover over a station for its grid, distance and when it was last heard, or click it to put it in the To box.

• This pass only: shows only stations heard during the current pass, or the last one while the satellite is below the horizon.
• Fade after: stations not heard for this many minutes fade, and disappear after twice that time.
• Zoom: use the mouse wheel or the + and − buttons, and drag to move around. Whole world (or the 0 key) zooms back out. Callsigns stay the same size as you zoom, so crowded areas such as Europe spread out.
• Clearing the Heard stations list also clears the map.

Sending your position

Send Position transmits your location through the satellite, so you appear on maps such as aprs.fi when a ground station gates it to the internet. It needs the APRS format. Hover over the button to see exactly what it will send. OscarWatch uses a GPS fix less than two minutes old first, then the latitude and longitude in Settings, then the centre of your grid square.

On the APRS tab of Terminal settings you can choose how precise it is, the map symbol and a short comment. The pictures in that list, and the markers on the pass map, are the aprs.fi symbol set by Heikki Hannikainen, OH7LZB. About 2 km (the default) and About 20 km blur the position, and Grid square centre sends only the middle of your four-character grid square, so your exact location is not shared. To keep the satellite free for contacts, you can send a position at most once a minute, and Terminal never sends one on its own.

Logging

With Log contacts automatically on (the default, on the Logging tab), a contact is saved once you and the other station have both sent a grid or report, and a roger or 73 has gone either way. It works whether you answered their CQ or they answered yours. Contacts are saved to the current logbook with mode PKT, propagation mode SAT and the satellite name and frequencies, and are uploaded to Cloudlog when that is set up. Press F12 to log the station in the To box at any time.

Acknowledge numbered APRS messages, on the APRS tab, sends an automatic acknowledgement for APRS messages to you that ask for one. It is off by default because each acknowledgement uses satellite time on a busy pass.

You Heard Me (UHM)

On a busy pass a reply can be lost even though the other station heard you. UHM on OscarWatch.org fills that gap: it tells you when a station you heard has also reported hearing you, through their own software. To use it, save your OscarWatch.org API token in Settings → OscarWatch, then tick Enable UHM on the UHM tab of Terminal settings. Test connection checks the token and warns you if the account callsign differs from the one Terminal transmits.

• Terminal reports stations whose frames are addressed to you. It does not report CQs, beacons, telemetry or your own frames, and reports the same station at most once every 30 seconds.
• For the stations you are working, the UHM column shows Wait, Heard me, Mutual (you both heard each other) or Expired. User means that station uses UHM on this satellite.
• Match on message text also sends the text of the frame, so UHM confirms the exact message.

APRS-IS gateway

On the APRS-IS tab you can pass the packets you hear on to the APRS internet system, so they appear on sites such as aprs.fi. This makes you a receive-only gateway (an iGate): Terminal never transmits anything it gets from the internet. You need an APRS-IS passcode for your callsign; Get your APRS passcode explains how. Without a valid passcode the server lets you log in but quietly drops what you send. Packets marked NOGATE, RFONLY or TCPIP are never passed on, and repeats within 30 seconds are dropped.

Modem settings explained

The defaults suit the ISS and most stations. These notes explain what each setting does if you want to fine-tune.

Transmit timing (Modem tab)

• Modem TX delay (ms): how long the modem sends a steady pattern after keying, before the message, so your radio and the receiving station have settled. 300 ms suits most FM radios; with CAT keying or a fast data port, 150 to 200 ms is often enough.
• Modem TX tail (ms): a little extra after the message so the end is not cut off. On the ISS keep it at 30 to 50 ms. A longer tail keeps you transmitting while the satellite is already repeating your frame, so you can miss it. Terminal settings warns you if it is too long.

Channel access (Modem tab)

• Duplex: Automatic follows the satellite's link type, which is right almost every time. Half duplex is for one-frequency satellites such as the ISS: the modem listens for a quiet channel and mutes its own receiver while sending. It listens again as soon as it unkeys. A copy of your own packet is treated as an echo. Full duplex is for satellites with the uplink and downlink on different bands, where you can hear your own frame coming back while you send.
• Persistence and Slot time (ms): when the channel goes quiet, the modem does not always send at once. In each slot it decides at random whether to go, so several stations waiting for the same quiet moment do not all transmit together. Higher persistence means it sends sooner.
• Maximum wait (ms): how long the modem waits for a quiet channel before giving up on that frame.
• Turnaround guard (ms): the short pause after transmitting before the modem may transmit again, so you do not transmit over the digipeat. The receiver keeps listening. A copy of your own packet is an echo.
• Wait for a clear channel in full duplex too: normally off, because in full duplex you hear yourself and the channel would always seem busy.

9600 baud G3RUH

Some satellites (for example LASARsat or KNACKSAT-2) use 9600 baud G3RUH on the radio's flat data port, not through the speaker or microphone. On the Modem tab, set Modem rate to Automatic when you pick the satellite from the database, or force 9600 baud G3RUH manually. Connect the USB or data cable to the radio's 9600 packet port. On the Soundcard tab, choose a 48 kHz capture device if Windows offers one, and set the separate TX level (9600 G3RUH data port). Put the radio menu on 9600 packet yourself; OscarWatch does not switch 1200/9600 over CAT yet. Duplex (half or full) works the same as for 1200 AFSK. Keep rig Doppler correction enabled for 9600 satellites: each CAT tuning step moves the FM discriminator baseline on the data port, and the built-in modem recentres within about 10 ms, but uncorrected Doppler drift still needs the same tracking you use for SSB/FM passes.

Decoding and safety (Modem tab)

• Transmit watchdog (s): stops any transmission that runs longer than this (10 seconds by default). A packet transmission is normally under a second, so this only trips if something has gone wrong.
• Bit fixing: a frame with one damaged bit would normally be thrown away. Bit fixing tries flipping a bit and checks whether the frame then makes sense, which rescues some weak frames. Single bit is the safe default.
• Frequency-offset decoders: on by default. Extra decoder banks at ±175 and ±350 Hz help copy ISS and other FM downlink packets when Doppler CAT steps leave the audio tones slightly high or low. Turn off on a very slow PC if processor use is a concern.
• Do not transmit while the satellite is below the horizon: on by default. Untick it only for ground-based packet.
• Decode WAV file: plays a recording through the modem without transmitting, for example a pass you recorded. It is a good way to check the decoder works before your first live pass.

If the soundcard stops delivering audio (Windows sometimes does this when you change sound settings while OscarWatch is running), OscarWatch notices within a few seconds and reopens it.

Using Direwolf or UZ7HO instead

You can still use a separate soundmodem application if you prefer, or if a satellite needs a mode the built-in modem does not have, such as BPSK or GMSK. The built-in modem supports 1200 baud AFSK (speaker or microphone audio) and 9600 baud G3RUH on the radio data port. Terminal shows a warning and blocks sending if the focused satellite needs something else.

1. Turn on the application's AGWPE server. In Direwolf, put AGWPORT 8000 in direwolf.conf (it is on by default in most builds). In the UZ7HO soundmodem, open Settings → Devices and tick the AGW server, port 8000.
2. On the Modem tab of Terminal settings, set Connection to AGWPE (Direwolf, UZ7HO soundmodem). Leave the host as 127.0.0.1 if the application runs on the same PC.
3. Press Test and list ports to check the connection and choose the Radio port.
4. Enter the application's TXDELAY and TXTAIL as Modem TX delay and Modem TX tail, so OscarWatch knows how long each transmission lasts.

With a separate application, its own settings handle the audio levels and push to talk, and the Soundcard tab, the waterfall and the Q column are not used.

Using a KISS modem or TNC

KISS is a simple way of passing packet frames between an application and a modem. Direwolf offers it over the network, and many hardware TNCs and radios with a built-in TNC offer it on a serial port. Terminal can use either.

KISS over TCP (Direwolf)

1. In direwolf.conf, put KISSPORT 8001 (it is on by default in most builds).
2. On the Modem tab of Terminal settings, set Connection to KISS over TCP (Direwolf). Leave the host as 127.0.0.1 and the port as 8001 if Direwolf runs on the same PC.
3. Press Test connection. KISS sends nothing back, so a successful test means the connection opened. Check the message log for received frames during a pass.

KISS serial TNC

This suits hardware TNCs such as the Mobilinkd and NinoTNC, and radios with a built-in TNC such as the Kenwood TH-D74 and TM-D710. Put the TNC in KISS mode before connecting. OscarWatch does not send any command to switch the TNC into KISS or back out of it, so a TNC that starts in its own command mode must be switched by its own menu or software first.

1. Set Connection to KISS serial TNC.
2. Choose the COM port and Baud rate of the TNC (often 9600, or 57600 or 115200 for USB TNCs). If the port is also used by the radio, rotator, GPS or FT4 push to talk, a warning shows and Terminal will not open it.
3. Press Test connection.

KISS settings

• KISS port: 0 for a TNC with one radio port. Dual-port TNCs use 1 for the second port.
• Persistence and Slot time: how eagerly the TNC transmits on a busy channel. The defaults (63 and 100 ms) suit most stations.
• Full duplex: leave off unless the TNC should transmit without waiting for a clear channel, for example on a crossband satellite where you hear your own downlink.
• Modem TX delay and Modem TX tail are sent to the TNC as its TXDELAY and TXTAIL. Keep the tail at 30 to 50 ms on simplex satellites such as the ISS.

These settings are sent to the TNC each time Terminal connects. If the connection drops, Terminal reconnects on its own, as it does with AGWPE.

Yaesu FT-847

The FT-847 cannot hold separate receive and transmit frequencies on the same band over CAT, which the ISS needs. For each frame Terminal sends, OscarWatch moves the radio to the uplink frequency just before keying, keeps it there for the transmission, then returns to the downlink. If the radio cannot be moved, the frame is not sent and the status line says so. Frames sent by another application go out on the downlink frequency. See Yaesu radios for more.

Problems?

• Nothing appears in the message log: check the satellite is above the horizon and radio control is tracking it. Look at the input level in the status bar: it should move while you hear noise or signals. Check the Waterfall tab for packet bursts on the 1200 and 2200 lines.
• Input level stays near 0%: check Input (from the radio) is the radio's sound interface, not the PC microphone or a webcam. Turn up the radio's data output or the Windows recording level. Some radios only send audio to USB in data mode, or have a menu setting for the USB output level.
• Input level shows clipping: turn the radio's data output or the Windows recording level down until it reads 30 to 70%.
• Packets on the waterfall but nothing decodes: the level may be too low or clipping, or the radio may be off frequency. Check radio control is correcting for Doppler.
• Your frames never come back as MY DIGI: check the radio actually transmits (PTT method), the transmit level with a test tone, and the uplink frequency. On the ISS, keep the TX tail at 30 to 50 ms.
• "Not sent: the satellite is below the horizon": wait for the satellite to rise. For ground-based packet, untick the horizon setting on the Modem tab.
• "Not sent: the channel stayed busy": the modem heard a signal for longer than the maximum wait. If the input is only noise, the receive level may be too high, or try a longer Maximum wait.
• "Transmission stopped by the watchdog": push to talk or the soundcard output got stuck. Check push to talk and the transmit watchdog on the Modem tab, and the output device on the Soundcard tab.
• "Modem: cannot reach 127.0.0.1:8000": only when using Direwolf or UZ7HO. The application is not running, or its AGWPE server is off or on another port. For KISS over TCP the same message means Direwolf's KISSPORT is off or on another port.
• KISS serial connects but nothing decodes or sends: the TNC is probably not in KISS mode, or the baud rate is wrong. Switch the TNC to KISS with its own menu or software and check the baud rate.
• UHM says the token was not accepted: create a new token on OscarWatch.org and save it in Settings.

Words used here

Word	Meaning
Packet	Sending text over radio in short bursts of tones that a computer decodes.
Frame	One packet burst, carrying who it is from, who it is to and the message.
Digipeater	A digital repeater, here on a satellite, that receives a frame and sends it straight back down.
AFSK, 1200 baud	The standard packet mode: two audio tones (1200 and 2200 Hz) sent at 1200 bits a second.
Soundmodem	Software that turns frames into tones and back, using the PC's sound interface. OscarWatch has one built in.
APRS	A widely used way of formatting packet messages, positions and status reports.
iGate	A station that passes heard APRS packets on to the internet.
SSID	A number after a callsign (as in MM9SQL-7) to tell apart several stations run by one operator. Use 0 for satellites.
PTT, VOX, CAT	Push to talk keys the transmitter. VOX keys it from audio. CAT is the radio's computer control connection.
Simplex, half duplex	Sending and receiving on one frequency, so you cannot listen while you transmit.
Crossband, full duplex	Uplink and downlink on different bands, so you can listen while you transmit.
Doppler	The frequency shift caused by the satellite's speed. OscarWatch corrects the radio for it.
AOS, LOS	Acquisition and loss of signal: when the satellite rises above and sets below your horizon.
Deviation	How far an FM signal swings in frequency, which sets how loud you sound. About 3 kHz suits packet.
AGWPE	A standard way for applications to talk to a separate soundmodem such as Direwolf or UZ7HO.
KISS, TNC	A TNC (terminal node controller) is a hardware packet modem. KISS is the simple framing many TNCs, and Direwolf, use to pass frames to an application.