[amsat-bb] Thoughts on ISS packet switch back to 145.825 MHz (long)

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Sat Apr 15 23:50:52 UTC 2017


Earlier today, I tweeted a quick comment about what I saw on
the ISS 145.825 MHz digipeater just after 1900 UTC this
afternoon. Since tweets are limited in length, I'm posting a
longer message here...

In the past few weeks, once word got out that a replacement for
the failed Ericsson VHF HT on the ISS was being sent up to the
station, many were anxiously looking forward to seeing the ISS
digipeater move from 437.550 MHz back to 145.825 MHz, where it
had been until the old radio's failure in mid-October 2016. I
understood that many would welcome this change, but I was not
jumping up and down with excitement. Unfortunately, after
seeing the activity on the ISS digipeater in the past day or so
since the replacement VHF radio was put on 145.825 MHz, my
worries have been confirmed.

For many, the move to 437.550 MHz meant many stations that could
easily work 145.825 MHz would have to change. Whether it was a
different antenna for the 70cm band or dealing with Doppler with
the 437.550 MHz frequency, almost all of the unattended stations
that had been present on the 145.825 MHz frequency were gone. If
you wanted to use the ISS digipeater to work other stations, this
was a great opportunity. Many stations using APRS-ready HTs and
mobile transceivers were showing up, using a group of memory
channels to compensate for Doppler, and were making contacts. Some
fixed stations, including those already capable of satellite
operating, were also showing up. Even on the busier passes, the
437.550 MHz always seemed to be clear of the clutter from the
unattended stations that previously inhabited 145.825 MHz.

Fast forward to yesterday (Friday, 14 April). The ISS digipeater
switched to 145.825 MHz in time for afternoon/evening passes over
Europe (around 1330-1400 UTC). Lots of stations showed up, based
on looking at the ariss.net web site. The same thing started to
happen here in North America, later in the day. The passes I worked
last night were not bad, but there were more stations on one pass
that went over much of the continental USA than I'd typically see
on 437.550 MHz.

By midday today (1900 UTC), it seemed like many more stations were
on the frequency. I saw 11 other call signs on a pass just after
that time this afternoon. At best, there may have been 4 or 5 other
operators at their keyboards or keypads, looking to make contacts.
The others were just squawking away, not answering APRS messages
sent to them. By the time the ISS footprint was reaching the east
coast, the frequency was congested. Lots of position beacons were
coming through, but not much of anything else. This is not new;
Clayton W5PFG wrote about this about a year ago, here on the
AMSAT-BB list:


For the two passes I worked this afternoon, around 1900 and 2035
UTC, I made two QSOs on the earlier pass, and one on the later
pass. A shame, considering there were so many other call signs
on the earlier pass, and even some rare spots - stations in DM44
in northern Arizona and CM86 in Santa Cruz CA were seen.

It is interesting that hams want to have their stations squawk on
145.825 MHz when nobody is at the keyboard. It could be doing it
24/7, no matter if the ISS is in view or not. Would anyone
think of setting up their satellite station to automatically
transmit their call sign and location every 15/30/60 seconds to
SO-50, unattended? I think not! That could be a violation of
the regulations, and would definitely be poor form by that operator.

Bob Bruninga WB4APR has a couple of documents with recommendations
for beacon intervals when working the ISS digipeater. One mentioned
a 5-minute interval for unattended stations:


Another document recommends that unattended stations should be in
"receive ONLY mode." (emphasis is Bob's):


I agree with the latter. If your station is unattended, why have
it transmit at all?! It may be different for less-populated parts
of the world, where gateway stations may transmit and then receive
their beacons from the ISS, which will show up on ariss.net and
other sites. For Europe, and definitely North America, the gateways
really don't need to transmit if they are unattended. There should
be activity on most passes, maybe even late into the night, to
know 145.825 MHz on the ISS is up and running.

Please don't misunderstand me... I think it is great for hams to
set up gateway stations listening on 145.825 MHz for the space-borne
APRS activity (ISS, NO-84, even NO-44 when it gets enough power to
transmit complete packets). But these stations, like other stations
that aren't operating as gateways yet transmit automatically,
shouldn't contribute to the congestion on the frequency.

I know I am in the minority on the ISS digipeater moving back to
145.825 MHz. Between the unattended stations clogging up the
frequency and some local interference I hear on 145.825 MHz around
my house, having the ISS on 437.550 MHz was fun! I worked it from
home, and on some of my road trips in the past 5+ months. Even for
some of my last NPOTA activations at the end of 2016. I'll continue
to work the ISS digipeater, almost exclusively with my APRS-ready
HTs (TH-D72A, or TH-D74A), looking to make QSOs by exchanging APRS
messages with other stations. If you can work packet from your
station, and we are in the same footprints, I hope to hear you (and
see you on my screen) soon. Like W5PFG mentioned a year ago, let's
get more stations on 145.825 MHz making QSOs...


Twitter: @WD9EWK

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