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[aprssig] KC2TUA/KC2UFG Ballon QRM

Keith VE7GDH ve7gdh at rac.ca
Mon Mar 23 16:05:09 UTC 2009


Bob WB4APR wrote...

> I have to stand by my statement. The impact on each digi is still only
> the same as one mobile at a one minute rate. Surely that does not do
> damage to any local area that has all kinds of guys driving around at
> a 1 minute rate wasting air time during their commute which no one
> cares about. While a balloon taking no more bandwidth is sure a lot
> more interesting.

So you are condoning a two hop path of WIDE1-1,WIDE2-1 from 75,000 (or
even 100,000+) feet that will trigger the fill-in digis as well as the
WIDEn-N digis, and with 1 minute rate? Sure, your statement is correct.
It doesn't make it good practise. I could say the APRS part of flight
was planned by someone lacking common sense (it took me a while to tone
that down) and I would be correct too. You can't have it both ways. If
it's OK for a balloon to beacon with a 1 minute rate and a two hop path,
then it's OK for all those mobiles that you care so little about. It's
just that the balloon could have a 250,000+ square mile footprint, and
nearly everyone out to the balloons horizon hears it without the digis.

> Dropping the rate for long duration mission would have been prudent.

There are a few things that would have been more prudent. I'd rather be
discussing beacon rates and paths than an aircraft with a couple of
hundred people onboard brought down by a balloon and payload sucked
into a jet intake. I'm sure they didn't plan on being at "cruising
altitude" for so long. According to their "blog" it didn't respond to
their cut down command. Sure, a NOTAM was issued, but mistakes can be
made. Unfortunately, it would appear that their APRS path and beacon
rate went exactly according to plan.

> The APRS channel is never clear when you are above 1000 feet, I
> guarantee it. That is why all balloons and aircraft are recommended to
> ignore DCD while in flight, else they will never transmit...

That was my point. Obviously they would have to ignore DCD. It's just
that they could have used a much more intelligent path. Everyone can
hear them without the two hop path without getting a couple of
digipeaters involved. Except for doubles, everyone would hear the
original, the first "local" digi that the balloon triggered, and likely
the second "local" digi that they triggered. It's just like "one more
mobile" in the local area... but that area could be almost a third of
(or at least a good chunk of) the eastern seaboard for the duration of
the flight.  Did you try playing back a log file of the event? The
balloon spent almost as much time going backwards as it did drifting
downwind. There were many delayed reports. 4253 position reports made
it to an IGate, but that's counting about 115 while it was still on the
ground before launch. As you say, it's just like "one more mobile"...
but everywhere. The 4,000+ beacons really translates to up to 12,000
beacons including the copies heard via digipeaters. The delayed reports
are possibly symptoms of digis that are too busy. You can't blame the
balloon for the digi being busy. It was likely busy before the balloon
left the ground. However, it does make it a more busy. One day, someone
will be looking for a missing ham that didn't make it home, or a SAR
team that didn't report back to base. Those delayed reports could take
up valuable time while someone figures out that the last known position
was somewhere else. The balloon is (in your words) just like  another
mobile "driving around at a 1 minute rate wasting air time during their
commute which no one cares about." It's not an overly likely scenario, 
but it could happen.

> Yes, this event got a lot of attention...

But for all the wrong reasons. I think we are still waiting to hear why
something onboard hammered away on the input frequency of a voice
repeater for a good chunk of the day.

> Anyway, looks like it was fun for all...

I'm sure a lot of people had fun with it. I enjoyed watching it. I wish
them success with future endeavours, but I also hope they spend a few
more minutes in the planning stages too. I'm sure there are places where
balloon enthusiasts get together to discuss to plan their flights and
optimum settings. On the other hand, it could be one mis-informed person
making all the decisions. Either way, balloon flights usually don't show
up on this list until they are off the ground and most of the time, it's
too late to change obvious goofs. Even though some equipment can be
re-programmed after launch, the success rate could be relatively low
if it was listening on 144.390 because the balloon hears "everything"
from cruising altitude . However, the ground station could hammer away
with no path at all until the command was heard by the balloon. The
ground station wouldn't be heard by anyone except by stations in the
immediate vicinity. No digis would be needed.

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




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