Satellite iGate Discussion

Discussion in 'Satellite and Space Communications' started by K3RLD, May 9, 2017.

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  1. K3RLD

    K3RLD Ham Member QRZ Page

    Figured I'd break this off from the ISS thread.

    I've officially re-configured my iGate to work as a standard APRS i-gate, just to see how it performs. Within 30 seconds of switching it over to 144.39, it already snatched 2 packets (neither of which is shown on aprs.fi, I'm assuming because typically I am not the "first heard".... not sure if I ever will be, but I figured I'd let it run and see what happens - edit: got a "first heard" from a local club digipeater while I was typing).

    I did this because after running for 24 hours, there wasn't a single successful capture of a packet originating from space (and there were several 60deg + passes). I'm assuming that the sensitivity of the RTL-SDR combined with the less than perfect ground plane are contributing to that).

    Not giving up, however. I'm going to finish my eggbeater antenna and re-try, and may attempt the ground plane antenna with a cheap TV amp as discussed in the ISS thread. I'll update here, feel free to discuss your own igates (as well as mine).
     
  2. AD5KO

    AD5KO Ham Member QRZ Page

    It's fun isn't it. :)

    This is all I have for today but I'm pretty sure it's caused by trees in full leaf... I'm working on it. Do you have a tree problem?

    # logresp GASR verified, server THIRD [Sun May 07 23:40:43 CDT 2017]
    K1WY>TQTU7T,RS0ISS*,RS0ISS,qAR,AD5KO:'dGRl -/] [Mon May 08 03:45:21 CDT 2017]
    KE0GUC-1>APDW13,RS0ISS*,qAR,AD5KO:!3843.30NR09037.91W& KE0GUC SGate [Mon May 08 11:53:42 CDT 2017]
    KC7MG-7>APK003,PSAT,ARISS*,qAR,AD5KO::K7JST-7 :ack 73{66 [Mon May 08 15:58:56 CDT 2017]
     
  3. K3RLD

    K3RLD Ham Member QRZ Page

    I have trees all around my house, but only to about 45° of my antenna, so really I should be good to go for these high passes.

    But this IS my first spring as a ham, so the leaves could be playing tricks on my reception. The iGate is working fine on 144.39:

    https://aprs.fi/info/graphs/a/K3RLD-10
     
  4. W5PFG

    W5PFG Premium Subscriber QRZ Page

    The specifications of the RTL-SDR dongles are such that you are going to have a very tough time copying any satellites on an omni antenna. Your major obstacle is RF noise from nearby devices. There is practically no filtering. A preamp will not help and probably would make things worse unless filtered.
     
  5. K3RLD

    K3RLD Ham Member QRZ Page

    Yeah, I realize that. But at $14, I'm going to give it a shot.

    [edit] so what's the SOP on using an amplifier and filter in series? Do you amplify the filtered signal, or filter the amplified signal?

    Can't find much on the subject - but my first guess would be amplify a filtered signal......
     
    Last edited: May 9, 2017
    AD5KO likes this.
  6. AD5KO

    AD5KO Ham Member QRZ Page

    There is a lot of hype around this subject and for the money the best thing you can do is try it for yourself.

    Amplifiers amplify everything but it is the radio that filters out the signals you do not want, portable radios have a harder time doing this because they lack the filters. In certain respects using an amplifier is no different that using a much bigger antenna, it also receives signals we don't want and portables have problems with that too when they are plugged into a big antenna for that reason.

    Using a cheap TV preamp is currently making the difference between my station receiving APRS and not receiving it at all. This applies to both of my systems where one of them is connected to an RF Concepts Amplifier with preamp built in and turned on. The results for each system are the same. And when conditions are right, both radios show 1 S unit of noise, and this particular model of TV preamp produces no more noise than the RF Concepts 2 meter preamp.

    But rather than listen to opinions it's better to try it for yourself. :)
     
    Last edited: May 9, 2017
  7. K3RLD

    K3RLD Ham Member QRZ Page

    Amp is ordered (local sprawlmart didn't have one).
     
    AD5KO likes this.
  8. W5PFG

    W5PFG Premium Subscriber QRZ Page

    Generally if I've commented on this subject it's because I've tried it myself.

    I own and have used the FUNcube Dongle and have a drawer full of RTL-SDR Dongles.

    The only compliment I can give to the RTL-SDR Dongles is that they are inexpensive. I have tried them on all the current crop of LEO satellites and wouldn't recommend them for regular use. If they were even remotely mediocre for regular VHF/UHF amateur radio use you would see a much more vocal user community.
     
    NJ4Y likes this.
  9. AD5KO

    AD5KO Ham Member QRZ Page


    I don't know anything about dongles, I have been reading about them a bit though but will probably stay with radios because my desire to receive a frequency is usually within the range of my radios. And I have no idea what plugging an amp into a dongle would do.

    I probably won't buy one because some of them cost more than 2 meter mobiles, and even a used 2 meter mobile is more useful to me.

    I am only talking about using preamps with radios.
     
  10. W5PFG

    W5PFG Premium Subscriber QRZ Page

    I have tried quite a variety of different ones and have come to my own conclusion that if it's a broad band preamp, it's often useless for satellites. Again, this is anecdotal evidence. It boils down to cost:benefit.

    The Ramsey kit preamp is often suggested for its low cost, but I highly doubt people actually have tried them. If so, they'd be disappointed.

    The AMSAT broad-band preamp is so-so, but I find it is better to invest in antenna and coax.

    Something like the Advanced Receiver Research, High Sierra Microwave, SSB Electronik or other band-specific RX amplifiers often deliver a measurable bang for your buck. I've tried or presently use a variety of them. Their performance metrics are amateur-band-specific.
     

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