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[aprssig] UAH ballooning report (long)

Jason Winningham jdw at eng.uah.edu
Sun Apr 10 22:36:15 UTC 2005


I have participated in several balloon chases over the past several 
semesters with the University of Alabama in Huntsville Electrical 
Engineering student's design teams.  Students spend one semester 
designing, building, and flying experiments for high altitude weather 
balloons.  Experiments on the various payloads have included: 
environmental sensors (temperature, pressure, gas concentration), ATV, 
video, still camera, motion stabilization for video camera, passive 
payload stabilization devices, solar power experiments, and cutdown 
mechanisms.  There are probably more, but these are all I can remember 
off the top of my head.

Here are some links to pictures provided by various students and 
volunteers, my TNC data, and APRS maps of the various flights:

http://www.eng.uah.edu/~jdw/balloonsat/

I think the program is working on an official site which I assume will 
contain student reports, data, etc.  In the mean time, you can look at 
the pictures on my unofficial site. (:  My relationship to the project 
is sort of tangential:  I work as a system administrator for the 
department where the balloon experiments are taking place, but I have 
no official status with the project.  I'm a ham who happens to work in 
the same place, so I get to see more of the projects than most.  I get 
to help out with ancillary aspects of the project such as building DF 
beacons and backup trackers.

I think on average our students do a really good job, considering they 
get introduced to the concept of a high altitude balloon experiment at 
the beginning of the semester and fly one that they designed and built 
before the end of that same semester.

Help from the amateur radio community has been extremely valuable.  UAH 
has recovered 100% (I think 19 for 19) of the balloon payloads 
launched.  This would not have happened without the help of many hams 
from all over the region: hams from Alabama, Tennessee, and Georgia 
have participated in the chase and recovery many times.

Bill Brown, WB8ELK, has been extremely helpful in all phases of the 
projects, sharing his ballooning experience with students and hams and 
generally helping us get successful flights and recoveries.  Thanks, 
Bill.

Last weekend's flight saw the test of Gary's (N4TXI) servo based 
cutdown mechanism.  Buzz Lightyear had an accident, apparently 
involving high levels of radiation, and parachuted from 80k feet with 
the help of the Buzz-O-Matic release mechanism and a single APRS 
message sent to the WhereAVR tracker, also designed and built by Gary.  
If anyone in the vicinity of the Alabama-Georgia state line between 
Rome and Fort Payne sees Buzz please email the address on his 
parachute.  Unfortunately, Buzz was not wearing a transmitter.  On 
yesterday's flight, the Buzz-O-Matic was the cutdown mechanism for one 
of the student payloads.  Bill also provided a wireless nichrome wire 
based cutdown for another balloon that functioned perfectly.

One thing that hasn't worked is connected mode communications with a 
KPC-3 on the balloon.  The students typically use a TH-D7, but using a 
D700 has also been problematic. The successful cutdowns were either 
triggered by a single APRS message (to the WhereAVR) or by DTMF tones.  
Even the DTMF tones didn't work when the students tried it with the D7, 
but my D700 at 50W did the trick.  Note the students were using 1/2 
wave mag-mount antennas (I think Diamond 770), not just a rubber duck.

A balloon chase is a lot of fun: last fall, I participated in once 
chase where I saw the first of two balloons launch, saw the first 
payload descending on it's parachute, and got to the right place to see 
the parachute of the second launch of the day dropping over the ridge.  
On a clear day the balloons are readily visible at altitudes up to 
burst, usually between 95k - 105k feet.  Last weekend I got so see the 
balloon burst.  A white cloud of dust (I assume talcum powder) was 
clearly visible.

Ballooning and APRS are getting people interested in ham radio.  I'm a 
ham because of what I saw with the balloon experiments, and I think 
others will be soon.

APRS is cool!  We have had flights in the past where one component or 
another of the APRS system failed; recovery via DF techniques using a 
small (10 to 30mW range) backup transmitter is not as much fun as 
simply driving to the coordinates on the map.  Student operated primary 
rigs have failed in the past due to power problems (old batteries, too 
few batteries, etc), wiring issues (connectors that don't lock), and so 
forth.  We have started flying backup trackers on 144.340 to help with 
this problem.  An opentracker, Garmin GPS18LVC, and a Yeasu vx150 with 
a 6xAA battery pack loaded with lithiums totals 17oz with insulated 
box.  This is a pretty small penalty to pay for the security of a 
backup rig.  Another benefit of the opentracker is the ease of 
configuration; novice APRS operators have trouble with the KPC3, even 
with step by step instructions.  The thing is just too crude and 
complicated.  I suspect in the future we will use the opentracker as 
the primary tracker, and fly the KPC 3 only if telemetry is required, 
or if connected mode communication is part of the experiment.

The Garmin 18LVC is a mouse type GPS that come with bare wires.  
because of packaging logistics I wanted to mount this GPS with the 
antenna facing the horizon (instead of the traditional and more 
sensible straight up), so I attached it to a test fixture (involving my 
daughter''s swingset and a drill) so that pointed toward the horizon, 
powered up from a cold start and spun it at about 100RPM.  the GPS 
locked and maintained lock under these conditions for about 10 minutes, 
at which point the test fixture failed.  I have since flown 3 GPS18s 
where the GPS was mounted vertically, top of the unit pointing toward 
the horizon, with zero problems.  I have also verified that if you get 
a GPS18PC and chop off the connectors, you have an 18LVC.  I understand 
this is not the case for the GPS18USB model, but can't confirm.

Xastir rocks!  On the last chase we had backup and experimental APRS 
stations on 144.34 and 433.775 in addition to the primary tracker on 
144.39.  My chase rig is xastir running on a Fedora Core 2 laptop 
tracking 3 different frequencies as follows:

144.390 - the Kenwood D700 was using its own TNC/APRS application on 
this frequency.  I connected an N0QBH ax.25 decoder 
(http://www.ringolake.com/pic_proj/decoder/rx_206.html) to the audio 
output of the D700 and fed 144.39 data to xastir.

144.340 - a TNC-X connected to a 2m mobile received this data.

433.750 - a Kenwood TH-D7 with its built-in TNC fed xastir this data.

A Garmin MAP60C, so we knew where  _we_ were.

Using Xastir, National Atlas and TIGER data, and GNIS data from USGS, 
it was trivial to find our way to the position reported on the map.

All the students who saw my xastir rig asked "Why aren't we using 
this?" They were using APRS+SA.

USB stinks.  I'm probably in the minority, but I do not like USB.  I 
don't like the way the drivers work with the USB to serial devices, 
simply because it's hard to be sure where they're going to show up.  A 
pair of these devices could be /dev/usb/ttyUSB0 and 1 when I hook them 
up, but swap places when I reboot.  This is annoying.  There should be 
some way to identify a specific serial port on a specific USB device 
that is consistent across reboots, and no matter where or when it is 
plugged into the USB bus (or tree).

USB also lacks a connector with a positive lock. Friction fit doesn't 
cut it in a mobile (or server room) application!

In case you're counting I had a total of 3 USB/serial devices and a 
total of 4 serial ports in use during the chase. I would appreciate any 
suggestions for solving my USB problems.

It's cold up there: beacons and trackers stopped working, evidently 
because the batteries stopped when the temperature dropped below 0C.   
I was irritated when this happened to me, since Energizer's spec sheet 
said they were good to -40C.  Uninsulated packages are not reliable.

SAW stabilized oscillators don't get it for APRS.  I spent a large 
amount of time trying to find where the little 70cm transmitter had 
drifted off to.  When it flies again it will be a simple CW over FM 
beacon.

Those are some observations, notes, and random thoughts.  If you have a 
chance, check out a balloon flight some time - it's a lot of fun.

-Jason
kg4wsv





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