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

Greg almetco at comcast.net
Sun Apr 16 23:37:09 UTC 2017


Simply, replace the ISS TNC with a human ear on an astronaut.  If 5 stations are calling him on one frequency and he/she cannot make out a callsign and says, “Again?” and this continues over and over, the QRM was on the uplink to the human ear by all 5 stations transmitting.  You can’t say it wasn’t QRM if he/she failed to respond to any callsign during a voice past.

My 2 cents, worth about a penny.

Greg
N3MVF
On Apr 16, 2017, at 7:30 PM, Jim Walls <jim at k6ccc.org> wrote:

Stefan,
I think you are the one missing the point.  QRM on almost any satellite path is on the uplink, not the downlink.  This is particularly true for modes that allow only one station to transmit at a time (specifically including packet).  If more than one person transmits on the uplink wherein their transmissions overlap, neither is properly decoded by the ISS, so nothing is transmitted by the ISS.  If this continues for the entire pass, there will never be any downlink transmissions.  By your definition, there was no QRM (because you could not hear it - but the ISS did), and you encourage more stations to transmit - thereby making the problem even worse.

Jim Walls
K6CCC


On 4/16/2017 15:18, Stefan Wagener wrote:
> Thanks Mike,
> 
> Again, you don't seem to get the point. Based on your setup, TNC, software
> etc you will NOT be able to decode every single packet and based on your
> setup and the ISS position the ISS digipeater will not re-transmit. It's
> the nature of the beast. No, you are not creating QRM if the ISS does not
> repeat your packet. Listen to the path of the ISS and you will hear that
> 50% of the time the radio is silent. It does not TX since there are no
> valid packets. Where is the QRM? There is none other than in you local
> environment where nobody cares. Don't discourage those that are trying to
> make it work. If you want a case, point out the stations and callsigns that
> create QRM and are not listenting/responding!
> 
> Just check out the last pass over the US. You will find 10 stations, that's
> a station a minute with room to spare. This is NOT SO-50!
> 
> 73, Stefan, VE4NSA
> 
> 
> 
> On Sun, Apr 16, 2017 at 5:05 PM, Mike Diehl <diehl.mike.a at gmail.com> wrote:
> 
>> Stefan,
>> 
>> I think you're taking Gabe's comment too literal. The point he's trying to
>> make is that many stations just keep on transmitting when they can't hear
>> anything.
>> 
>> We can use that amateur radio on ISS as an experiment as an excuse but
>> that doesn't really fly. APRS is beyond an experiment as it is a well
>> established form of using APRS via satellite, nothing new here.
>> 
>> Furthermore, what is the point of trying repeatedly to transmit if you
>> can't decode? It is the golden rule for a reason and it applies everywhere,
>> satellite or terrestrial. If you can't hear it you can't work it, bottom
>> line. Until you can decode packets you're just creating QRM.
>> 
>> 73,
>> 
>> Mike Diehl
>> AI6GS
>> 
>>> On Apr 16, 2017, at 2:46 PM, Stefan Wagener <wageners at gmail.com> wrote:
>>> 
>>> Hi Gabe,
>>> 
>>> With all respect I very much disagree. The amateur radio equipment on the
>>> ISS is an experiment! Sometimes it works and sometimes it doesn't. Based
>> on
>>> your location, equipment and ISS position you will* NOT* decode every
>>> packet, and yes that includes your own packets. So folks will be trying
>>> again and that's okay. *They don't become a source of QRM* on the ISS
>> since
>>> the ISS will only re-transmit if its a good packet. They are exercising
>>> their license privileges to work through the ISS and for many having that
>>> first digipeat after many tries is their success story and we welcome
>> that.
>>> 73, Stefan, VE4NSA
>>> 
>>> 
>>> 
>>> On Sun, Apr 16, 2017 at 1:43 PM, Gabriel Zeifman <
>> gabrielzeifman at gmail.com>
>>> wrote:
>>> 
>>>> I think the golden rule of working all sats applies to ISS as well: if
>> you
>>>> can't hear (or decode), don't transmit! It's easy to become a source of
>> QRM
>>>> if you keep transmitting in the blind when you can't hear.
>>>> 
>>>> 73,
>>>> Gabe
>>>> NJ7H
>>>> 
>>>>> On Apr 16, 2017, at 1:28 PM, Robert Bruninga <bruninga at usna.edu>
>> wrote:
>>>>> I agree completely.  ISS digipeting should be for LIVE operators.  Or
>> for
>>>>> LIVE things.... (a student experimental ocean going buoy for
>> example)...
>>>>> NOT for non-moving-fixed egos...
>>>>> 
>>>>> Bob, WB4APR
>>>>> 
>>>>> -----Original Message-----
>>>>> From: AMSAT-BB [mailto:amsat-bb-bounces at amsat.org] On Behalf Of
>> Patrick
>>>>> STODDARD (WD9EWK/VA7EWK)
>>>>> Sent: Saturday, April 15, 2017 7:51 PM
>>>>> To: amsat-bb at amsat.org
>>>>> Subject: [amsat-bb] Thoughts on ISS packet switch back to 145.825 MHz
>>>>> (long)
>>>>> 
>>>>> Hi!
>>>>> 
>>>>> 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:
>>>>> 
>>>>> http://amsat.org/pipermail/amsat-bb/2016-April/058200.html
>>>>> 
>>>>> 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:
>>>>> 
>>>>> http://www.aprs.org/iss-aprs/iss-tx.txt
>>>>> 
>>>>> Another document recommends that unattended stations should be in
>>>> "receive
>>>>> ONLY mode." (emphasis is Bob's):
>>>>> 
>>>>> http://www.aprs.org/iss-aprs/utiquet.txt
>>>>> 
>>>>> 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...
>>>>> 
>>>>> 73!
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> Patrick WD9EWK/VA7EWK
>>>>> http://www.wd9ewk.net/
>>>>> Twitter: @WD9EWK
>>>>> _______________________________________________
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>>>>> views of AMSAT-NA.
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-- 
73
-------------------------------------
Jim Walls - K6CCC
jim at k6ccc.org
Ofc:  818-548-4804
http://members.dslextreme.com/users/k6ccc/
AMSAT Member 32537 - WSWSS Member 395


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