[amsat-bb] Help decoding/understanding terrestrial packet heard on ISS freq 145.825 MHz

David L Warnberg dwarnberg at verizon.net
Fri May 1 21:44:48 UTC 2015

For the packet data take a look at UISS software... also for those SSTV
transmissions from the ISS look at RX-SSTV..

You will also need a packet engine...

Here is what I use

Packet Engine Pro  web site = http://www.sv2agw.com/
UISS and RX-SSTV  web site = http://users.belgacom.net/hamradio/

Hope this helps


-----Original Message-----
From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of John Brier
Sent: Friday, May 01, 2015 5:18 PM
Subject: [amsat-bb] Help decoding/understanding terrestrial packet heard on
ISS freq 145.825 MHz

Thanks for all the responses on SO-50 preamps and portable setups. I'm still
digesting the info.

TL;DR: I heard automated packet transmissions on the ISS packet frequency
when the ISS wasn't in sight and recorded them to try and figure out
who/what they are, but my software isn't decoding anything.
Can you help me understand what they were, or even better, decode them



Here's another question that has me excited:

Yesterday after having visited with family in Maplewood, New Jersey for
several days, I drove home to North Carolina. I knew there was an ISS pass
at 10:26 AM/1426 UTC, right when I started my trip, so I tuned to 145.825
MHz and heard its digipeater easily.

Then I left the radio on.

I'm not sure where I was in NJ, but about one hour later, around 11:33 AM
local/1533 UTC, I heard packet on the frequency again but I was confused
because there weren't supposed to be any more passes for a while. I
confirmed on my phone that the ISS was over some far away ocean at the time
I was hearing these new transmissions, so I knew they must be terrestrial.
Still, it seemed odd that someone or something was transmitting when the ISS
wasn't in sight...

Maybe it's an internet gateway I thought. Or do people leave their stations
on the ISS frequency 24/7 so they can "work" any pass that happens?

I tried recording videos of the transmissions for later decoding to figure
out who or what it was. Eventually I realized it was transmitting every 2
minutes. It was almost certainly an automated setup, adding credence to the
idea that this was an internet gateway.
Unfortunately, before I realized that, and after recording one video of it,
the best reception I received during my drive by "pass," I wasn't recording.
As I drove further away it only got weaker and weaker. I did manage to get
two half way decent recordings of it, but I have tried decoding them with
Soundmodem on Windows and it's not printing out anything like it normally
does. I am very new to packet, only becoming interested in it because the
ISS uses it, so I thought maybe someone else might be more equipped to
decode it. Or certainly someone could shed some light on what I heard, maybe
the operator in NJ is on this list.

I used Audacity to record the audio off the videos I made as well trim and
amplify the audio, but I haven't done anything else, though if someone wants
the unedited videos I can put them up too.



John Brier, KG4AKV, Raleigh, NC, FM05
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