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ZL3AI > APRDIG 10.11.03 02:19l 223 Lines 9103 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
TAPR APRS Special Interest Group Digest for Tuesday, November 04, 2003.
1. RE: Digitraveler antenna mods
2. RE: Balloon launch information
3. RE: Ballon launch information
4. RE: Digitraveler antenna mods
5. RE: Ballon launch information
6. RE: Digitraveler antenna mods
7. RE: Ballon launch information
8. How do I beam data bi-directionally, ie North to South and vise versa?
9. RE: Ballon launch information
10. RE: Ballon launch information
11. W0eee-3
12. Re: California Fires / Digi
13. APRS rigs
14. odd positions
15. Re: odd positions
16. Re: odd positions
17. Re: odd positions
18. Re: California Fires / Digi
19. Coverage Circles
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Subject: RE: Digitraveler antenna mods
From: "Scott Miller" <scott@3xf.com>
Date: Mon, 3 Nov 2003 21:52:56 -0800
X-Message-Number: 1
>Since the application of the digitraveler would likely have zero RF
>obstructions, and already performs pretty well with the internal antenna,
>with the unit sitting on a vehicle dashboard (which could block 1/4 of the
>sky view, or perhaps more), it seems silly to change the GPS antenna.
True, but at least for other projects I'd still like to hear if anyone's
done it.
>A 1/4 wave (or even better, a 1/2 wave) that's vertically polarized and
>omnidirectional is going to radiate most of the signal above the horizon,
>into space, and there are very few hams there to receive the signal.
What about a vertical with ground radials? Would that serve to depress the
pattern toward the horizon?
I've actually got a radiosonde antenna sitting on my desk here... it's
obviously for a much higher frequency but it's got what I take to be a
ground plane in the shape of a cone swept back at about 45 degrees. Hey,
I'm a software guy, not an RF engineer. You know what'd be cool... a 3D CAD
program where you could tweak antenna parameters and watch the radiation
pattern in real time. Does any such thing exist in the hobbyist realm?
I just got into the EOSS mailing list - I'll have to see if there's anyone
else in these parts (central California) doing this sort of thing. And
figure out how far inland I'm going to have to go to not wind up in the
Pacific.
Scott
N1VG
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Subject: RE: Balloon launch information
From: "Nash Clemens" <nclemens@calpoly.edu>
Date: Tue, 4 Nov 2003 0:2:31
X-Message-Number: 2
As long as you meet those requirements you are not required to apply for a
waiver but you DO need to file a NOTAM, I would also advise at least
notifying the FAA Flight Standards Office that controls the airspace you're
going to be flying in.
Ask to talk to the operations supervisor and just explain what you're doing
and if there is anything else you need to do. I developed a plan of action
and sent it in for them to look over and make sure they agreed that I
didn't need a waiver and that I was avoiding restricted airspace. Most of
the time they have no idea what is really needed but it's better to show
you're trying to be helpful and legal then just appearing on their radar
and being a general ass about it.
The Plan of Action simply detailed how I met, or was not required to meet,
the FAR 101 specifications. I also detailed out how I predicted my flight
path and the general procedures I would be following for notifying the FAA
up to and including the launch day.
One of the people I talked to was extremely helpfull and gave me the phone
numbers I would need to file the NOTAM, when I should, who I would actually
need to talk to and some stuff to try to avoid (ie major flight paths). As
long as you show you've read the FARs and are serious about doing it right,
I've had good experiences with talking with the FAA.
Nash
KG6PGG
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Subject: RE: Ballon launch information
From: matthew.cook@tekelek.com.au
Date: Tue, 4 Nov 2003 16:56:20 +1030
X-Message-Number: 3
>Jacob Tennant <k8jwt@adelphia.net> Wrote: Mon, 03 Nov 2003 17:26:40 -0500
>Was looking for some information about doing a ballon package launch for
>my local ham club/APRS groups. Not looking for anything too fancy to
>start, just maybe a APRS tracker and a friend has offered a mini-ATV
>transmitter.
>After watching KG4UWE-15 for a hour or two on Saturday I thought I might
>be able to get some new people out with a ballon/APRS/foxhunt combo
>since we would use APRS to foxhunt the ballon package as well as demo
>ATV in the process.
I stumbled across this link a while back, it's the best description of a
high altitude balloon launch that I've seen yet.
http://vpizza.org/~jmeehan/balloon/
The pictures are stunning and it carried an APRS tracker and full flight
computer. I think the video camera bag is a very neat idea for insulating
the whole device from the cold. The telemetry is also very interesting
and well presented.
Unfortuately we have strict laws down here in Australia that prevent us
from ever launching such a payload. We cannot even get approval to piggy
back our own Bureau of Meterology high altitude balloons either :-(
But then again they dont have rules on rockets yet >:)
73's
Matt
VK5ZMC
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Subject: RE: Digitraveler antenna mods
From: WA8LMF2@aol.com
Date: Tue, 4 Nov 2003 01:39:58 EST
X-Message-Number: 4
In a message dated 11/4/2003 12:57:34 AM Eastern Standard Time, scott@3xf.com
writes:
>What about a vertical with ground radials? Would that serve to depress the
>pattern toward the horizon?
>
>I've actually got a radiosonde antenna sitting on my desk here... it's
>obviously for a much higher frequency but it's got what I take to be a
>ground plane in the shape of a cone swept back at about 45 degrees.
Use a quarter wave ground plane consisting of a 1/4-wave whip or wire with
plug attached screwed into a socket with 4 1/4-wave radials soldered to
the 4 screwholes in the corners of the socket.
Theoretically with the radials straight out, you get a 37 ohm feed point
impendance. As you droop the radials downward to about 45 degrees ( like
your cone above) the feedpoint Z will increase to around 50 ohms for a
perfect match. If you continue to bend them straight down to create what is
now esentially a vertical dipole, the Z will rise to the typical 70 ohms of
a simple dipole.
The radiation pattern of this kind of 1/4 groundplane has it's major lobe
not at the horizon like a vertical dipole, but rather tilted upward about
20-25 degrees. Simply mount it UPSIDE DOWN on the bottom of the balloon
package to spray out RF over a rather large diameter circle centered
directly below the balloon. The lobe is fat enough that even people
directly beneath the balloon will easily get it as well as people near the
horizon as seen from 50,000 or 100,000 feet.
This is exactly the same scenario that Bob is always advocating for PCsat
(quarter wave whip on a car roof groundplane taking advantage of the
radiation angle uptilt to reach space) only upside down.....
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
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Subject: RE: Ballon launch information
From: "Scott Miller" <scott@3xf.com>
Date: Mon, 3 Nov 2003 22:55:29 -0800
X-Message-Number: 5
>I stumbled across this link a while back, it's the best description of a
>high altitude balloon launch that I've seen yet.
Yeah, saw that one. I've got a similar Soekris computer myself, but I'm not
quite ready to tie it on to a balloon and let it go. =]
>computer. I think the video camera bag is a very neat idea for insulating
I think he used in insulated lunch bag - even cheaper than a camera bag, and
with better insulating properties!
>Unfortuately we have strict laws down here in Australia that prevent us
>from ever launching such a payload. We cannot even get approval to piggy
>back our own Bureau of Meterology high altitude balloons either :-(
Major bummer. Why the heck not? You've got almost as much land area as the
US, and less than 1/10 the population. What, is it going to burst and hit a
sheep or something? =]
I was just out at the weather station about a mile from my office the other
day and was fortunate enough to get to launch one of their balloons - had to
test out the computer system I'd just fixed, of course. =] One of the guys
there said there was even talk of commercial cell phone providers flying
miniature cell sites on gov't radiosondes to fill in gaps in their networks.
It's kind of painful, though, to watch perfectly good GPS units flying away
twice a day. Or once an hour during launch countdowns...
Scott
N1VG
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