[aprssig] Trans-Atlantic APRS Balloon Flight Wed 29 April!

Robert Bruninga bruninga at usna.edu
Tue Apr 28 10:39:00 EDT 2009

The beacon freq is on 40 meters on 7.102.55 
and not 10 meters this flight.

>> It is unfortunate that there may be some 
>> 1-packet-per-minute QRM to four VHF voice 
>> repeaters along the way that operate on 
>> 145.41 with an input of 144.81. 
> Some ... repeater users, the repeater coordination 
> group and the FCC very well could see it as willful 
> and intentional interference...

Yes, your point is well taken.  So I believe the launch team for
this historic event is making every effort to inform those
possibly affected repeaters.  The balloon team has researched
and identified four possible 145.41 repeaters that may be
affected, and is attempting to contact those groups.

> Lets put it another way.  You going to have 
> 100's of repeater users dusting their old 
> TNC's off, and decoding the input. I sure 
> wouldn't want my call on it.

I think there maybe several mitigating procedures that the
balloon team is working on to minimize any impact.  First, they
are attempting to contact those repeaters.  Next, they are
enlisting the aid of APRS operators in the area of those
repeaters to also be on hand to coordinate with those local
groups.  Third, the fligh path over those areas is between about
midnight and dawn.  Fourth, repeaters that use PL will not be
impacted.  There are only four on that frequency in the flight
path.  The TXD is being made short so that the length of the
packet is under the 1 second time of the ker-chunk filter on
most modern repeater controllers so that they will ignore it and
it wont wake anyone up.

Yes, I agree that a PIC controlled frequency shift based on
longitude could have been the prudent approach.  Another simple
method that does not need a GPS is to use a 556 tone decoder
chip hooked to a diode detector on say one of the VHF TV
channels.  If it detects 60 HZ, then it is over the USA and can
operate on 144.39.  If it detects 50  HZ, then it is over
Europe.   Of couse when the switch to all digitial is complete
in the USA, this method will no longer work.

Anyway, just some thoughts...  I am not condoning the operation,
just providing the background I have been able to find out...  


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