[amsat-bb] APRStk ? Or other?

Scott scott23192 at gmail.com
Thu Mar 2 21:34:42 UTC 2017

The only way that I am aware of to cover two different frequency’s APRS traffic on the same Pi would be to run two separate SDR’s under two different running programs.

This should not be a problem since the command string very specifically defines not only the SDR device being used, but also the frequency to tune and what config file to use settings from.

For example, here is my 70cm ISS iGate command string:

rtl_fm -f 437.550M -d 0 -s 48k - | direwolf -l /home/pi/igate/iss-uhf-log/ -c /home/pi/igate/iss.conf  -r 48000 -D 1 -

... please note the “-d 0” argument after the “rtl_fm” command.  That specifies SDR device #0, which is my case also happens to be the ONLY SDR attached to that particular Pi.  You can also plainly see the frequency and other settings.

I honestly can’t recall if I have tested it or not, but to run another iGate session with a second SDR, you would run a similar command except to tune a different frequency, specify a different SDR device, and use a different .conf file for your direwolf settings.  Most people would want to specify a different log file as well.



From: Mike Thompson 
Sent: Thursday, March 02, 2017 1:52 PM
To: Scott 
Cc: amsat-bb at amsat.org 
Subject: Re: [amsat-bb] APRStk ? Or other?

I wonder if it would be best to run 2 RTL's on a Rpi for use on both 144.39 and on UHF for the ISS, or is it just as effective to run one.

On Thu, Mar 2, 2017 at 10:08 AM, Scott <scott23192 at gmail.com> wrote:

  I was also concerned about that at first but on most passes I log a significant number of packet receptions, so while adjusting for RX doppler might help to some degree, it’s definitely not a deal-breaker.

  (I also learned not to judge your effectiveness by the number of packets you iGate to ariss.net; it appears that duplicates only show up once.  So, to REALLY know how well you’re doing, check the log file on the iGate or use an external app to monitor it on another PC)



  From: Mike Thompson
  Sent: Thursday, March 02, 2017 11:01 AM
  To: Scott
  Cc: amsat-bb at amsat.org
  Subject: Re: [amsat-bb] APRStk ? Or other?

  I wonder how hard it would be to get the raspberry pi to download TLE's every now and then, and apply doppler correction to the downlink iGate frequency. on 70cm, this might be a big deal.

  On Thu, Mar 2, 2017 at 9:56 AM, Scott <scott23192 at gmail.com> wrote:

    Hey Dave.

    It takes longer to read the instructions that it does to setup a Raspberry Pi to be an iGate.

    When the ISS digipeater changed to 70cm, there were not enough iGates so I thought it might be fun to throw one together.  There are numerous how-to's online, but this one is perhaps the most straight-forward:


    ... unfortunately, the way the document was created you won't be able to copy/paste commands.  But regardless, it's not a difficult process if you have even the slightest familiarity with a Pi or linux in general.

    Hope that helps!

    -Scott,  K4KDR
    Montpelier, VA  USA


    -----Original Message----- From: Dave via AMSAT-BB
    Sent: Thursday, March 02, 2017 9:57 AM
    To: amsat-bb at amsat.org
    Subject: [amsat-bb] APRStk ? Or other?

    Hi All

    I'm setting up an autonomous sat gate using a spare Kenwood TMD700. I seem to remember that once upon a time there was a DOS program called APRStk that could Doppler correct the TMD700.

    Does anyone know of a more up to date alternative that would run on a Pi or Pi Zero?

    Dave EI4HT / M0GIW

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