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[aprssig] KC2TUA/KC2UFG Ballon QRM

Keith VE7GDH ve7gdh at rac.ca
Sun Mar 22 16:30:12 UTC 2009


Bob WB4APR wrote...

> Yes, each digi will put out one packet once a minute from the
> balloon. But that is no different than any other mobile driving
> around at a one minute rate.

Absolutely incorrect. The mobile is only heard by the adjacent digis. A
balloon at 30,000 feet is impacting every digi (and every other APRS
user) over an area of about 75,000 square miles, plus a couple of hops
outside that circle. From 100,000 feet the impacted area is probably
more like 200,000 to 250,000 square miles.

> Basically it has added one new mobile into the local area of each such
> digipeater for the duration of the flight (probably about 3 hours or
> so). This should not be that much of a problem in each of those local
> areas...

Yeah, but potentially into the "local area" of scores or even hundreds
of digis, and it doesn't listen to see if the frequency is clear. I'll
agree on the last point though that it usually only goes on for a few
hours. The high beacon rate with a mult-hop path from a high altitude
increases the balloons "chance of success" to the detriment of every
APRS user out to the horizon. It also sets a bad example.

> As to its being multi-hop. That too should not be a problem in the
> APRS WIDEn-N system, since each digipeater under the New-N Paradigm
> will digipeat the packet once and only once no matter how many
> additional copies it hears.

There's absolutely no need for it. It's trivial for the balloon to
beacon at one rate with a multi-hop path on the way up and again on the
way down below a certain altitude... with a respectful slower rate when
it is high and with no path at all, or at the most, a one hop WIDE2-1.

> One minute might seem excessive, but then the Balloon might be going
> 100MPH or more when it hits the jet stream, and the owners reallly do
> have to hurry to get to the end point and stay within speed limits...

The chaser should stay within speed limits no matter what. If it is
expected to reach the jet stream, more planning and probably more
chasers are needed. Either way, it's just equipment. If the balloon
comes down before they get there, it's too bad. It would be nice to
recover the payload, but not the end of the world if it isn't found.
Sure, if it was mine, I'd like to take video of the actual landing as
well as recover it, but joe public shouldn't be put at any more risk
than a foam cooler coming down at parachute speeds, and by a chaser
driving at the speed limit with a navigator sitting beside him.

> and balloons do change course at different altitudes. AND when the
> balloon breaks, the path down may be at thousands of feet per minute.

No parachute? I wouldn't want to be picnicing with the kids at the
impact point.

> SO I do not object to these typical 3 hour missions at 1 minute
> rates...

Those 3 hour missions have absolutely no impact on me and probably very
few people on the west coast of North America. However, I can still see
the harm of fast beacon rates with multi-hop paths from 30 (or 100)
thousand feet. As you mentioned, the harm is temporary. Someone gets to
do something really neat... which I would enjoy doing if I had the
opportunity. It can just be done better though.

> The reason for the multi-hops is for when the balloon lands on
> the ground and the serach team might need to be lucky to find
> it, and it might go much further (at 100 MPH) than they can get
> to before it hits the ground. So the 2 hops helps them in the
> final search (though it does no damage at altitude as noted in
> the above paragraph).

As mentioned, it is trivial to modify the beacon rate and path (and
anything else) based on the altitude and or even a number of other 
factors. Just because you aren't apparently aware of the technology 
doesn't mean that it doesn't exist. The threshold for toggling the 
beacon rate and path should be determined by the topography on the 
ground and the digipeater density over the expected route.

> I hope that helps...

Not really. It sounds like you are condoning high beacon rates with a
multi-hop path from high altitude. Other than the fact that the event
will be over in a short time, the only thing I can really agree with is
that there won't be any ping-ponging with up-to-date digis. We just need
to get balloons operating with up-to-date equipment and practises too.

73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"




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