Talking Satellites

Last edit Aug. 2021

I thought about putting together some helpful information for working on satellites, a very beautiful and challenging area, where the efforts are fully rewarded.

There are many satellites for amateur radio traffic, either digital or voice repeaters, or that send weather maps with the earth from space. Astronauts from the International Space Station sporadically establish links with radio amateurs and interview students from schools. You can receive all these transmissions, plus there are SSTVs with anniversary occasions, communications between EVA participants and other stuff that occur all the time.

Most of the connections are in the VHF / UHF, are made with low power (4-5W are sufficient) and last very little, maximum 10-15 minutes, because this is what it takes the satellite to pass over your head. It’s not like the ground connections, where you have enough time, so the preparation beforehand is very important.

Before you start working, stop and read this good operating practices.

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Ideally, you need an all mode VHF/UHF transceiver, like the old Yaesu FT-857, or the newer fancier ICOM IC-7000. First of all, the transceiver must be connected to the audio interface of a computer. Received audio signal go to LineIn-soundcard and Speaker-soundcard must reach the station’s microphone – for transmission. All solutions are already described on the net. Some stations have a dedicated connector for this. It resembles the PS2 computer jack.
Image result for ham radio data connector

There’s still the PTT problem. If the radio has VOX, you’re good. If not, you need to do a VOX circuit. Like here. By means of a CAT cable, the radio’s frequency can be controlled by the computer (Doppler correction and stuff…)

ANTENNA. I think, the most important element.
Related image
I did this (left image) and it works great.
Here is a very good site.
And here there are other antennas, good for inspiration.
For a fancier experience, one can use an antenna rotator and a pair of cross Yagis (VHF and UHF). Check my work here for rotator and here for cross Yagi.

SOFTWARE very necessary. All free.
Orbitron – Satellite Tracking System. With a huge database, you can track the orbit of hundreds of satellites and make predictions when they pass over you.
MixW – Multimode software for radio amateurs. Make digital connections via ISS or other satellites. Decode a lot of digital modes, you can periodically broadcast for APRS, make logs …
SDR# – SDR software (software defined radio). Find a lot of plugins for all kinds of decoding – directly or through the sound card.

MMSSTV – Slow Scan TV with Windows and Soundcard. For sending / receiving images. Many modes, automatic recognition, templates.
WXTOIMG – The world’s best weather satellite (WXsat) image decoder. Decodes weather images transmitted by NOAA satellites with the Earth’s globe from space.

FOR MOBILE DEVICES – still free.
Cover art
ISS Detector – See the Space Station. Track the Space Station, make predictions, set alerts.


Cover artHeavens Above – Track a lot of satellites and make predictions when they will come across, find satellite information as up/down frequencies, see what’s above right now.


Cover artAPRSdroid – is an Android APRS reporting tool. Send and receive APRS with your mobile phone and a portable radio station, connected with an audio cable.
Here you will find one of the many connection examples, with explanations for setting up the station and the phone.

SITES of great help to prepare, work and see what you have done. – The Radio Amateur Satellite Corporation – almost all satellites on which radio amateur traffic can be made. STATUS, SOFTWARE, FREQUENCIES – a site dedicated to links through the Space Station repeater. See who sent and if you were heard. – schedule of SSTV transmissions on ISS – about voice transmissions / interviews with ISS astronauts – a large database with CALLSIGNs and various news. – positions map (APRS) transmitted by citizens and received and put on the net by various servers. Also to see if anyone received you. – map with the positions of transmissions and receptions worldwide, in all bands. – satellites
tracker, orbits, predictions, information and space news.

The easiest way to start working on satellites, is with ISS and FM satellites.
This is a list of active FM satellites. For an update, check AMSAT site.

Satellite Uplink
FM (MHz)
FM (MHz)
(67 Hz CTCSS)
145.960 Operational – Due to battery status, please do not attempt to access while in eclipse.
(67 Hz CTCSS)
436.795 Operational. SO-50 has a 10 minute timer that must be armed before use. Transmit a 2 second carrier with a CTCSS tone of 74.4 Hz to arm the timer.
(141.3 Hz CTCSS)
145.900 Operational. FM transponder activated by schedule. The Amateur Radio Unit can operate either as an FM transponder or APRS digipeater. See for schedule. For more details, see
144.350 437.200 Operational, but rarely active. When FM transponder is not on, there is a telemetry beacon on 437.200 MHz (LilacSat-2 Home Page). The FM transponder is on no set schedule. For real time updates about which mode the satellite is in, see the AMSAT Live OSCAR Satellite Status Page
AO-27 145.850 436.795 Operational. Currently active for four minutes on ascending and descending passes over mid-latitudes of the Northern Hemisphere
ISS Crossband Repeater 145.990
(67 Hz CTCSS)
437.800 Operational. See ARISS Status for status information
CAS-5A 145.925 435.600 Launch June 2021. Also includes 3 linear transponders. CW Beacon 435.570 MHz. 4.8k / 9.6k GMSK telemetry 435.650 MHz.
CAS-7A 145.950 435.455 Launch May 2021. Also includes 3 linear transponders. CW Beacon 435.430 MHz. 4.8k / 9.6k GMSK telemetry 435.480MHz. 1 Mbps GMSK Image Transmission 10460.000 MHz
CAS-7C 145.900 435.690 Launch May 2021. CW beacon 435.715 MHz
Tevel Mission 145.970 436.400 Launch Late 2020. 8 identical 1U CubeSats. Transmits 9k6 BPSK telemetry by default, can be commanded to operate as FM repeaters.
IO-86 (LAPAN-A2) 145.880
(88.5 Hz CTCSS)
435.880 Operational. Satellite is in a low-inclination low earth orbit and not visible north of about 30 degrees north or south of 30 degrees south. FM transponder operations are by schedule only. See for schedule updates.

– VOICE REPEATER = Up 145.990 MHz [CTCSS 67Hz], Down 437.800 MHz.
– PACKET/APRS = 145.825 MHz

– SSTV = 145.800 MHz / PD-120 mode
– VOICE Russian = 143,625 MHz
NOAA weather satellites
– NOAA15 – 137,620 MHz / bandwidth 30KHz
– NOAA18 – 137,9125 MHz / bandwidth 30KHz
– NOAA19 – 137,100 MHz / bandwidth 30KHz
See here how to receive and decode Russian Meteor-M2.

work in progress…
Any suggestion is welcome.