3 ms·

What is the use case of such repeater?

• arghwhat 6y ago
  Radio amateur experimentation and communication. That it is cross-band is just a detail that simplifies the repeater (single-band repeaters generally use humongous filters).
  • 082349872349872 6y ago
    Is the highly non-stationary nature of the repeater an interesting part of the experimentation? http://images.spaceref.com/news/2003/speedlimit.jpg http://images.spaceref.com/news/2003/speedlimit.jpg
    • arghwhat 6y ago
      Of course. You'll have to adjust for the Doppler shift (about 7kHz swing during a pass IIRC), and depending on your antenna design you might have to do precise tracking during the pass. There are also sub-sports such as QRP that tries to perform communication using very low power levels, which makes everything much more challenging, including the already slightly tricky contact with the ISS. I believe the current QRP record is 1.6 billion miles-per-watt, with 1 microwatt making it from Oregon to Alaska (1650 miles).
  • prox 6y ago
    But if the ISS passes over in just a few minutes, is that useable?
    • arghwhat 6y ago
      You have a ~10 minute window every ~90 minutes IIRC. The HAM sport is mostly about establishing contacts of increasing difficulty, not about making boring, rock-solid reliable communication links. 10 minutes is plenty for that, and helps stop people trying to hog the thing as only one person can be received at a time. Outside experimentation (e.g. trying an antenna, transmitter or receiver design), the HAM radios on the ISS are also used for school-astronaut contacts.