Useful Information for Starting Amateur Radio Satellite Operations

Useful Information for Starting Amateur Radio Satellite Operations

On this page you can find some useful information for those planning to start amateur radio satellite operations. This page will be updated as I learn more and please do check back for updates. Information presented at present is for Low Earth Orbit (LEO) FM satellites.

Basic setup

Basic setup you need is a dual band directional antenna covering VHF and UHF and two hand held radios. Another option is to connect a full duplex hand held radio with a duplexer to two antennas. Limited success is also possible by using vertical antennas. I am using an omnidirectional CP22E VHF antenna for both uplink and downlink, along with a dual band base station. Recommened antenna is a dual band VHF/UHF antenna, preferably a cross Yagi with circular polarization. Directional antennas need rotation in the direction of satellite movement in both azimuth and elevation. Uplink is the frequency on which you transmit to the satellite. Downlink is frequency which you receive from the satellite. Satellite transponder receives on your uplink frequency and retransmits the received signal on the downlink.

Various downloadable apps are available which give realtime tracking of the satellites, like Heavens Above. While working outdoors, if the antenna is very light, it can be used as a hand held antenna, and rotated. But as it could lead to hand fatigue, it is better to use a tripod with an arrangement for rotation in azimuth and elevation. For working from inside the shack, you need directional antennas with an antenna rotator which can move the antenna in both azimuth and elevation, with a controller.

Doppler tracking

When the satellite appears above the horizon, it starts moving towards you. The time at which it appears above the horizon is called Aquisition of Signal (AOS). So the downlink frequency is higher than the real frequency of the downlink. It comes down gradually as it reaches the Time of Closest Approach (TCA). After that the satellite is moving away from you and the frequency falls below the real frequency of the downlink. The time at which the satellite disappears below the horizon is called as Loss of Signal (LOS). High end radios have automatic Doppler tracking facility.

I use the Argentinian Amsat webpage for Doppler tracking manually, as I am working from within the shack, using a base station. I keep the website on a mobile phone and follow the Doppler correction. An alternate page is available from LU7ABF. Correction for Uplink is different and moves upwards from below the real frequency from AOS to LOS. Those using hand held radios generally program 3 or 4 four steps above and below the nominal frequency, for both uplink and downlink and change them as the pass progresses from AOS through TCA to LOS.

Frequency Chart of FM Satellites

SO-50 has a 10 minute timer which has be activated by sending a two second carrier with a CTCSS tone of 74.4 Hz. Further access is with 67 Hz tone. Programming a default tone of 67 Hz for all satellites will do no harm, except for the satellites with a different tone requirement. Tone should not be programmed for the downlink frequency. It is only for the uplink. Squelch should be kept fully open for the downlink and the hissing sound should be there. When the satellite signal is being acquired by the radio, the hissing sound of the open squelch suddenly stops and you can listen to the station callsign.

Communication through satellites

Communication through satellites is limited to callsigns, grid square and signal report. Only this way can more number of operators utilize the limited time available during a given pass of a LEO satellite which is usually less than 10 minutes. Prolonged CQ calls are to be avoided. Short calls followed by a good listening period is a must. Otherwise those hearing your CQ calls will not be able to respond. Though overhead passes are good for beginners, low angle passes are needed for working DX. That needs a high gain directional antenna and meticulous Doppler tracking. When the number of elements on Yagi antenna is increased, gain increases, but beam width decreases. Low beam width high gain antenna will be more difficult to point in the direction of satellite movement, especially for a beginner.

Timing of activation of satellites

International Space Station (ARISS) which is one of the easiest to work because of the 5 watt output of the downlink, is usually on through out, except during scheduled maintenance periods. Current status of ISS ham radio stations webpage announces the status and scheduled maintenance timings. ARISS – Amateur Radio on the ISS Twitter page is useful to contact the ground team. Schedules of Educational contacts and transponder ON/OFF timings are also posted on Twitter. ARISS beacon announces its callsign periodically on CW.

TEVEL series of satellites are activated depending on how their footprints overlap. Usually only one or two satellites are activated at a time, though occasionally three may be activated at a time. Twitter page of David 4X1DG gives the information on a regular basis. Activation of each satellite is usually for a period of 72 hours. There is a webpage from DF2ET which gives live Satellite Timer Status for TEVEL series, UVSQ-SAT, PO-101 and LilacSat-2. That gives a count down timer for the active satellites in the TEVEL series as well as UVSQ-SAT and PO-101.

AO-91 was a favourite of many FM bird operators in the past. The battery status is currently low and it may work during daylight passes. Female synthesized voice announces FOX 1D Beacon. LILAC Sat 2 is active for 24 hours at a time, starting around 2200 UTC on Mondays, Wednesdays, and Fridays. Activation time of PO-101 can be obtained from the Twitter page Diwata2PH. Twitter page of UVSQ-SAT and their project page are useful to know about it. 

AMSAT Live OSCAR Satellite Status Page is useful to know the recent status of the satellites. All those who hear satellites are encouraged to submit data at this page. If the satellite has not been reported active recently, there is obviously no point in wasting time to access it. FM Satellite Frequency Summary page lists a few more satellites and some which are yet to be installed and activated and some which are yet to be launched as well. It can be seen that some of them have linear transponders in addition to FM transponders.

SatMatch

SatMatch is a site which helps you to know whether there are overalapping passes for satellites between your grid and grid of another radio amateur. Minimum data input needed for the site are the satellite name, Western grid and the Eastern grid. It gives you the overlapping passes and period of overlap between the two grids in the coming 24 hours. There is also provision for checking the previous days’ passes and future passes as well.