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

17 Apr 2017

      Greg,
Thanks for the read. My point was just general simplex leaving protocols and other factors out just to keep it simple. Like you point out, adding in overhead we loose even more time.
The major problem though is that the terrestrial stations can't hear each other so the door is wide open for collisions. Which is why unmanned beacons are trouble.
I think what is being lost here is what is happening at the bird. It's not like a linear or FM transponder on full duplex where we can hear what is happening. We all know when we have a dead carrier on voice because the bird is instantly transmitting what it hears. Now in the case of simplex if a dead carrier was thrown at ISS for the whole pass then how exactly would we know? One could assume nobody was on.
Lots of packets heard from the station can prove a lot were heard and decoded properly. A lack of packets can indicate two things, either it wasn't receiving a lot or there were too many. That's the point I've been trying to make this whole time. Beacons should be seen for what they are, stations just simply increasing the odds of collisions at the ISS receiver.
73,
Mike Diehl
AI6GS
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On Apr 17, 2017, at 7:45 PM, Greg D ko6th.greg@gmail.com wrote:
I believe APRS Packet is basically an Aloha network.  See https://en.wikipedia.org/wiki/ALOHAnet
18.4% is the theoretical limit...  Yes, surprisingly low.  See the article for the math behind it.
Greg  KO6TH
Mike Diehl wrote:
...
Congrats Stefan, you still have no idea what ISS heard, only what it digipeated. Please also prove me wrong that a simplex channel can support more than 50% utilization. The fact only 5% of the pass had the ISS radio transmitting can either prove nothing or support the fact that there is so much QRM AT THE ISS that very few complete packets were heard and digipeated.
As far as black listing goes the FCC has no authority over what data a site decides to exclude from showing. Sorry but you're reading and not comprehending what I stated.
73,
Mike Diehl
AI6GS
On Apr 17, 2017, at 5:30 PM, Stefan Wagener wageners@gmail.com wrote:
...
Well Mike,
Here is my log from the last pass. It shows 29 digipeats (~75% decoding success at my station) for 8+ minutes. Each packet is barely 1 1/2 seconds! That is a utilization of less then 5% assuming my math is correct.
In addition, asking for "blacklisting of licensed operators" is something I certainly will not support and fortunately neither does the FCC.
73, Stefan, VE4NSA
..........................................
Fm RS0ISS To CQ <UI pid=F0 Len=36 >[18:46:17] >ARISS - International Space Station 
Fm KE7ZXE-4 To CQ Via RS0ISS <UI pid=F0 Len=28 >[18:47:17]
N7UWX DE KE7ZXE from CN86 me 
Fm VE6PW To U1PSWQ Via RS0ISS,ARISS <UI pid=F0 Len=32 >[18:47:59] `*Zvl _-/` Hello  via  ISS   _%  
Fm RS0ISS To CQ <UI pid=F0 Len=36 >[18:48:18] >ARISS - International Space Station 
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:49:51]`p0Kl p[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:50:01]`p0Kl }[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:50:11]`p0Kl j[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm KD0KZE To TUPX8Y Via RS0ISS <UI pid=F0 Len=49 >[18:50:17] `yaHl _-/ Greetings via ISS from Circle Pines MN  
Fm RS0ISS To CQ <UI pid=F0 Len=36 >[18:50:18] >ARISS - International Space Station  
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:50:24] `p0Kl O[/>CQ: Via ISS de W8LR Middletown Ohio= 
Fm KD0KZE To TUPX8Y Via RS0ISS <UI pid=F0 Len=49 >[18:50:28] `yaHl _-/ Greetings via ISS from Circle Pines MN  
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:50:35] :KD0KZE   :599 Via ISS de W8LR Jerry{62
Fm KD0KZE To TUPX8Y Via RS0ISS <UI pid=F0 Len=49 >[18:50:39] `yaHl _-/ Greetings via ISS from Circle Pines MN  
Fm N7EKY-6 To T6PY2T Via RS0ISS,WIDE2-1 <UI pid=F0 Len=36 >[18:50:49] 'u&Bl _-/]CQ via ARISS,EN56jd,Paul= 
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:50:55] :KD0KZE   :599 Via ISS de W8LR Jerry{62
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:50:58] :N7EKY-6  :599 Via ISS de W8LR Jerry{63
Fm KD0KZE To TUPX8Y Via RS0ISS <UI pid=F0 Len=49 >[18:51:01] `yaHl _-/ Greetings via ISS from Circle Pines MN  
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:51:11] `p0Kl w[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm W8LR To S9SR2V Via RS0ISS <UI pid=F0 Len=47 >[18:51:21] `p0Kl"F[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm W8LR To S9SR2U Via RS0ISS <UI pid=F0 Len=47 >[18:51:38] `p0Kl!%[/>CQ: Via ISS de W8LR Middletown Ohio=  
Fm KD0KZE To TUPX8Y Via RS0ISS <UI pid=F0 Len=49 >[18:52:07] `yaHl _-/ Greetings via ISS from Circle Pines MN  
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:52:10] :KD0KZE   :599 Via ISS de W8LR Jerry{62
Fm W0BSH-3 To S8SW6R Via RS0ISS <UI pid=F0 Len=16 >[18:52:10] `v06l _>/]"5v}=  
Fm N7EKY-6 To T6PY2T Via RS0ISS,WIDE2-1 <UI pid=F0 Len=36 >[18:52:16] 'u&Bl _-/]CQ via ARISS,EN56jd,Paul=                      
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:52:27] :N7EKY-6  :599 Via ISS de W8LR Jerry{63
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:52:30] :N7EKY-6  :599 Via ISS de W8LR Jerry{64 
Fm W8LR To APK003 Via TS0ISS <UI pid=F0 Len=40 >[18:53:13] :N7EKY-6# :599 Via QSS de W8LR Jerry{07
Fm W8LR To APK003 Via RS0ISS <UI pid=F0 Len=40 >[18:53:15] :W0BSH-3  :599 Via ISS de W8LR Jerry{65
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On Mon, Apr 17, 2017 at 4:51 PM, Mike Diehl diehl.mike.a@gmail.com wrote:
Greg,
You make a good point about the complications of dropped packets. I have some good recordings of voice stations getting a call back when as little as a single letter of their call was heard. It's amazing how well we can learn the voices of other ops when you're on regularly. This simply doesn't happen on packet.
Another complication is that it is on simplex. That means on a 10 minute pass the maximum amount of time possible to digipeat is 5 minutes if the channel is fully saturated. Subtract out the ISS beacons we end up with less than 50% of the pass available for ISS to hear you.
I'm not sure what the best solution is. You do bring up an interesting point about APRS-IS. Maybe it's possible to have them black list fixed beacon stations and remove the vanity aspect like you mentioned.
73,
Mike Diehl
AI6GS
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On Apr 17, 2017, at 1:26 PM, Greg D ko6th.greg@gmail.com wrote:
Gabriel Zeifman wrote:
...
It's not complicated. However much it may be insisted ISS packet is not
SO-50, it is practically the same thing (single channel operating on FM).
Actually, the ISS digi is worse.
With voice communication, one can sometimes pick up the start or tail of
a call sign, as the astronaut demonstrated, and use that to filter a
second try.  With digital, any bits that get corrupted result in no
reception at all.
I hate to suggest this, and admit I am assuming a cause without
supporting evidence, but it might be necessary to remove the "vanity"
aspect of ISS digipeating, and take down or hide from general view the
reporting sites that support it.  While a useful tool for
troubleshooting, I suspect the vanity aspect of seeing your call in a
public list day after day from an unattended station may be too strong a
draw for some, resulting in the clogged channel.  The SatGates that
monitor for ISS and other APRS satellite                     traffic are still important
part of the infrastructure, so that the information can be datamined
from APRS-IS if you need it for troubleshooting.  But the consolidated
lists of who has been seen digipeating through the ISS, I think, may be
contributing more trouble than they are worth.
Greg  KO6TH

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Mike Diehl

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