IO81QP  -  51.38.22N  -  02.39.48W


























Radio Contact With The International Space Station





After making amateur radio contact via the Mir Space station in 1999, I wanted to see if I could repeat the experiment, this time using the amateur radio and computer equipment on board the International Space Station.

Equipment changes and upgrades, advances in technology, along with improvements made in my radio shack here since my MIR contact, meant some changes in the method I would use this time around.

The first obvious change was in Packet radio equipment. The amateur radio Packet data network is more or less redundant now, being replaced by the widespread use of email via the internet, and most of the old  Packet bulletin boards have now closed.

However, Packet Radio AX25 data transmission is still very much alive in the form of APRS - the amateur radio Automatic Packet Reporting System developed by Bob Bruninga, WB4APR.

Information on the APRS system can be found here:


APRS uses the same AX25 data protocol generated by computer interfaced to a radio to send messages in real time. The main difference between the two systems is that unlike the old Packet system, the data terminals do not need to 'connect' to each other, prior to exchanging information, so these transmissions are more of a 'broadcast' type, sent across the APRS radio network. 

 A quick look at an APRS internet server such as: 


will demonstrate the variety of amateur radio stations using the APRS system. Another obvious difference between Packet Radio and APRS is the use of maps. The addition of GPS equipment means that mobile stations can send a position beacon at intervals, allowing their movement to be tracked. Fixed stations can program their position into  APRS software and announce their presence and location. Real time weather data can also be transmitted, and I run this type of system here, sending a weather beacon every 15 minutes. Weather stations on the network are identified by a 'WX' icon at their station position on the map.

Some APRS stations are configured as 'gateways' and these relay transmissions heard by their radio equipment onto the internet where they are picked up and displayed by sites such as mentioned above.

Some of the amateur radio satellites also have APRS equipment fitted, which is capable of re-broadcasting any data packets heard back onto the APRS radio network.  The amateur radio station installed on board the International Space Station  carries such equipment, so I decided I would use this and see what would happen.

Advances in computer technology have resulted in the old data terminals, such as the Kantronics KAM used in my MIR contact, also becoming redundant. Whilst a data terminal could be used, most APRS data transmissions from stations operating from a fixed location use the computer sound card to generate the audio tones used by the APRS AX25 system, these being encoded / decoded  by suitable computer software.




A web search gave me a link to UISS software specifically designed for contacts with the ISS. This software can be found at:  


Setting up the software is simple, following the clear installation instructions available at the web site, and the online forum for UISS users. Please note though, UISS requires the AGW Packet Engine software from:



Yaesu FT-847


Interfacing the FT-847 to the sound card is easy using a ready made cable such as one available from Radioarena at:


The antenna in use was a simple Watson 2meter VHF vertical which is my normal setup for that band.

I decided I would use two computers for this experiment. One running Ham Radio Deluxe radio control software, and one running  UISS which would control the Push To Talk (PTT) line to enable transmission from the radio.

 Ham Radio Deluxe (HRD) software comes complete with a satellite tracking program, and unlike my MIR setup, I could now compensate for Doppler Shift in the radio signal. This would make it possible for me to use more of the satellite pass window. Doppler effect moves the radio frequency off center as the satellite is moving, and HRD will correct for this by constantly re-tuning the radio to maintain the correct center frequency relative to the ISS APRS frequency of  145.825 MHz

HRD can be found at:

As I already had my FT-847 radio connected to the computer soundcard for my PSK-31 setup, and was therfore used to transmitting using a soundcard, all I had to do was follow the first rule of amateur radio (listen, listen, and listen again, before transmitting) as I wanted to see the format of the messages other stations were using.

Now came the problem. The Space Station APRS equipment is switched off from time to time, especially during shuttle missions. As usual here, I managed my experiment to perfectly coincided with one of those periods of down time...  




I kept an eye on the ISS Fan Club web site at:


  which gives the operational status of the various transmission opportunities available from the Space Station. Eventually my patience was rewarded and the APRS equipment was switched back on.

Having successfully received and decoded several messages from Hams transmitting through the Space Station, I was now ready to try my hand.

The UISS configuration I used, showed 'CQ' in the 'To' box on the UISS command screen. For 'Via' I used 'RS0ISS-4,Wide2-2' and my location was programmed in on the UISS setup screen. My 'APRS Position Text box showed '30W-Chepstow UK, IO81QP, 73's Alex'

'30W' is the output power in watts I was using, and 'IO81QP' is the Maidenhead locator for my home. 'Wide2-2' is the setting which controls the number of digipeater (data repeater) satellite gateway stations forwarding on my signal. I was hoping to get my transmission successfully repeated back to earth via one of these, and see it appear via the internet.  73's is Ham Radio short hand for 'best wishes.'

A suitable overhead orbit was predicted around 0800 on 2nd October 2010, so, while watching the position of the Space Station on one monitor, I transmitted from the UISS software. 

At the end of the pass I checked the internet site: 


This site shows all the APRS transmissions to and from the International Space station, and I was pleased to see my call sign  appeared on the list. My transmission had been 'heard' and decoded by G7JVN-6, a satellite gateway located in Hastings, UK, and then repeated to the internet.

My next job was to post a QSL card to ARISS (Amateur Radio on board the International Space Station) to confirm my contact, and I received their card back the following week:





The ISS Fan Club issue various certificates of achievement for receiving or transmitting via the ISS, and apart from gaining a memento of the contact, this is also a good way to donate to the maintenance of their web site.


ISS Fan Club Achievement Award


I hope the above inspires you to try a contact through the International Space Station, and of course, other satellites are available...