ISS Inspiration

Discussion in 'Satellite and Space Communications' started by G0VKT, Nov 13, 2021.

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  1. G0VKT

    G0VKT Ham Member QRZ Page

    I have been so lucky in my nearly 40 years in my interest in all things radio. Things that have kept my interest and taken me in new directions. A whole series of happy accidents that has kept this ham hobby alive. Please forgive my waffle but I am so excited right now about something new to me.

    Ages ago I put an app on my phone to alert me me to when the ISS might be visible. I had forgotten about it as I stopped getting alerts. Towards the end of September it suddenly started giving me alerts. Looking at the ISS status I knew that packet was active. I changed the app settings to alert me whenever it passed nearby and not just at night when it is visible. Not seen it recently, but in early October I copied the packet transmissions. It was great to observe the doppler shift on 2m using one of my RSP SDRs.

    Later in the month, whilst listening to a a pass on the packet frequency, I could see a signal in the waterfall. Tuning to that frequency I could hear voice. It was an ARISS contact from the station to a school in France. WOW! So cool and by chance! All this just on a Discone.

    I think it was a couple of weeks ago that the repeater was switched back on.
    Since then none of the passes have happened when I was at home or awake. Then, last night , I got an alert of a pass. Went to the UHF downlink frequency, expectations were low, but I could hear it! WOW again!

    I do know that the doppler effect is more pronounced at UHF when compared to VHF. It was fascinating to actually observe it.

    The next pass at my QTH in the UK is this evening and I will listen again. I am now researching what other birds that I can hear.

    I am so interested in the birds now. Never thought about it before.

    I now have a winter project to actually work through a bird. On a budget, using what I have and portable.

    For Rx - An RSP SDR. A Raspberry Pi and a small touch screen.

    For Tx - An HT. Probably the Baofeng that I have.

    Antenna - Homebrew copy of an Elk/Arrow.

    Any tips would be gratefully received.

    Paul G0VKT
     
    K6CLS and KA2CZU like this.
  2. KH6IDF

    KH6IDF Ham Member QRZ Page

    You should be able to work the ISS crossband repeater with the equipment you have. If you can set up the Baofeng to transmit on 2 meters and receive on 70cm you wouldn't need the SDR. I have worked stations thru the ISS repeater with just a dual band vertical antenna outside and a FM dual band 5W transceiver (FT-817ND) inside.

    Full duplex is not necessary, half duplex works fine the only limitation being you can't hear yourself while transmitting.

    First step is to listen, which you have already done. If you set up 5 adjacent memory channels with the same TX frequency (145.990) and slightly different RX frequencies (437.810, 437.805, 437.800, 437.795 and 437.790), you can switch memory channels to follow the UHF Doppler shift (no need to do this on 2M). Just start on 437.810 and switch to the next channel when the audio starts to sound like it is off frequency. You only have to switch channels every 30 seconds to a minute or so, not too difficult to do.
     
    AK5B likes this.
  3. G0VKT

    G0VKT Ham Member QRZ Page

    Thank you. I am an experienced HF ham. Satellites are new to me.

    Paul G0VKT
     

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