Working ISS on UHF/VHF

The above contact was completed via the cross band repeater that is aboard the International Space Station using the following equipment.

Radio: Yaesu FTM-300 Antenna: Comet GP-6

While K9KSU made the contact from his base station setup, the same can be accomplished using a dual band hand held.  The hand held radio will make it a  bit more challenging,  However, it is possible with patience, good timing, and a little bit of luck.   Hearing the ISS is easily accomplished when the pass is favorable.

Here is a list of things to consider when starting your quest for using the ISS repeater:

•  You will need to know when the ISS is "visible" in your location.

  • • There are many apps available for your smart phone that will give you the current position and forecast of the ISS.  One popular app is called ISS Detector.  ISS Detector iOS and  ISS Detector Android

• You will need to program your radio to use the repeater. 

  • • Unlike terrestrial repeaters, the ISS is moving at 17,500 mph.  This creates the need to take doppler shift into account when selecting the frequencies for TX & RX.

    • Program 5 different memory slots to use during the entire pass of the ISS overhead.  Each memory slot with different doppler shift consideration. The typical ISS pass lasts for 3-6 minutes.  It's fast pace action.  Programming memory slots ahead of time takes a lot of the workload away during the pass. 

    • The ISS repeater uses  tone PL 67

  • Open up the squelch

    • It is necessary to open the squelch on your radio.  Transmissions from the ISS are typically weak signals, some are even way down in the "weeds". 

  • Listen first.... talk later.

    • The ISS repeater is a busy place and there is a general order and etiquette.  Listen to a few passes.  Get to know the decorum before jumping into the conversation.

    • It is very seldom that you will find an astronaut on the other end of the repeater.  Generally what you will hear are terrestrial stations exchanging call signs and maidenhead grid square locations. But unlike our local repeaters that make 60 mile contacts possible - the ISS repeater can facilitate contacts of several thousand miles.

    • Remember that the overhead pass time is very limited and is limited for everyone else too. Make your contacts short and to the point.