[amsat-bb] Unsuccessful attempts to make APRS contacts through ISS or NO-84

KO6TZ Bob my.callsign at verizon.net
Mon Dec 26 17:08:31 UTC 2016


This very topic was part of the discussion this morning over the 
satellite XW-2A.

There are several items involved.

First - Although NO-84 PKT is currently APRSON, most of the time it is 
APOFF.  If it is apoff, you will not get a reply.

Second - It is my belief the timing of the APRS Digi on the ISS is set 
too short.  This would be the Response Time and TXDelay settings.  Many 
of us report hearing what is probably the digi of our packet, but it 
does not display on our terminal.  The packet is probably being 
"clipped" at the beginning preventing decode.  The absence of a RED 
packet prompts a resend.  There is no way of knowing if you doubled with 
another station or just did not decode your packet, so you just resend 
increasing the traffic on the Simplex frequency.

Third - Since a simplex frequency is being used, there are times when 
there is a lot of doubling on both the uplink and downlink directions.

Solution - For NO-84, give it a try again today and check the status on 
the web site.

For ISS, try turning off the CAT (C-) just before sending near TCA, to 
see if that works.


I've been trying and trying to make APRS contacts through ISS (UHF) and
NO-84 (VHF) for some time now and have been unsuccessful in all attempts
even in cases where the bird was plenty high or right over my head. Here's
my working conditions..

Icom IC-9100 using a microKeyer II (MKII) as the interface. SatPC32ISS,
UISS (Pro Version), UZ7HO Soundmodem. The antenna array is a m2 Leo-Pack
and the rotator is a Yaesu G5500 being controlled with a Green Heron AZ-EL
unit. All software is the latest. Doppler shifting is working fine as
SatPC32ISS, IC-9100, and GH controller are talking to each other without
issues. I've listened to the outgoing sound of the packet and did not hear
anything unusual. In almost every case I've tried the lowest power and
increased power at varying levels without luck. I've monitored the outgoing
audio and adjusted the TX on the MKII to varying levels to make sure the
audio of the packet was not over cooked.

 >From what I can tell everything is working well together and I can see
incoming packets from other stations decoding on UISS and Soundmodem.
However when I TX... No hits whatsoever. When I tested the system on the
local APRS frequency it works fine and other stations are digipeating my
packet signal.

I'm coming to the conclusion that this must be a problem with my settings
in either Soundmodem or perhaps UISS. The packets going up never get
repeated. On both birds I use CQ & Ariss (Tried others too) during the
outgoing TX attempts but nothing. I would really like if someone who uses a
similar setup and has things working to contact me.

I'm at wits end and now curtailing any further attempts until I get some
information on what may be going on..

Steve Nordahl, NS3L
Nazareth, Pa.

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