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

Jeff Moore tnetcenter at gmail.com
Fri May 1 22:11:40 UTC 2015

I could be wrong, but it's possible you may have heard a different
satellite transmitting.   It's also possible and more likely, you heard
someone with their APRS or Packet station on the wrong frequency.   This
occurs occasionally with certain dual band radios with built in packet
modems like the D700/D710 or the Alinco 635 in that they are in a packet or
APRS mode and for whatever reason, the operator changes to a different
frequency on that side of the radio w/o shutting off the data
capability.    It can happen on single band radios as well but not as
often, it's easy to do it with the dual band radios.  This occurs all to
often all over the country.  I hear it once or twice a month on repeater
and simplex frequencies in my area so I know it's a widespread occurrence.

7 3
Jeff Moore  --  KE7ACY

On Fri, May 1, 2015 at 2:18 PM, John Brier <johnbrier at gmail.com> wrote:

> 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
> yourself?
> http://cupcakecarnival.net/sites/default/files/New_Jersey_Terrestrial_Packet_145825_2015-04-30-1540_UTC_one.wav
> http://cupcakecarnival.net/sites/default/files/New_Jersey_Terrestrial_Packet_145825_2015-04-30-1540_UTC_two.wav
> 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.
> http://cupcakecarnival.net/sites/default/files/New_Jersey_Terrestrial_Packet_145825_2015-04-30-1540_UTC_one.wav
> http://cupcakecarnival.net/sites/default/files/New_Jersey_Terrestrial_Packet_145825_2015-04-30-1540_UTC_two.wav
> John Brier, KG4AKV, Raleigh, NC, FM05
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