Date: Wed, 2 Mar 94 04:30:45 PST
From: Ham-Space Mailing List and Newsgroup <ham-space@ucsd.edu>
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Subject: Ham-Space Digest V94 #45
To: Ham-Space
Ham-Space Digest Wed, 2 Mar 94 Volume 94 : Issue 45
Today's Topics:
GPS information (2 msgs)
Portable Oscar 13 Station?
Satellite FAQ answers (long)
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Date: 28 Feb 1994 20:18:08 GMT
From: unix.sri.com!headwall.Stanford.EDU!beale@hplabs.hp.com
Subject: GPS information
To: ham-space@ucsd.edu
Keith: (sorry, email to you bounced)
Concerning GPS: not what you want to hear perhaps, but I suspect that a
nearly-finished GPS receiver module is the cheapest way to go. Now that
the radio front-end has been pretty highly-integrated by high volume
manufacturers, do-it yourself GHz spread-spectrum recievers don't make
so much sense.
Do you get QEX (the ARRL Experimenter's Exchange, available from ARRL) ?
If not, you probably should! The February 1994 issue has: "Interfacing
GPS or LORAN Devices to Packet Radio" on p. 9-14. They discuss the
Magellan OEM 5000 board (12V at 250 mA, 3.5x7 inch circuit board)
which gives you RS-232 output of LAT/LON, altitude, and time in a
standard (NMEA) format. It was $445 and needs an external antenna
($60 passive, $130 active). They say that Magellan will be coming
out with a smaller GPS card for $295 in May, with binary output rather
than formatted ASCII.
Trimble Navigation (Sunnyvale, CA) also makes some OEM GPS modules,
although I am only aware of packaged units for use in cars/trucks,
and I haven't checked on the pricing.
I believe that a GPS reciever is a challenging project even for an
expert in both microwave and digital circuits, with access to a lot
of test equipment and a rather large supply of free time.
If your time is even differentially more valuable than exactly zero,
I think buying is the way to go!
Best,
John Beale
n8juf
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Date: 28 Feb 1994 22:26:06 GMT
From: pa.dec.com!nntpd.lkg.dec.com!nntpd.lkg.dec.com!waf@decwrl.dec.com
Subject: GPS information
To: ham-space@ucsd.edu
Keith,
My E-mail bounced as well. E-mail or post a good address if
you want a long message covering where to look for handheld units
whose prices I don't think that you can beat with straight home brew.
They are probably more expensive than you could get away with using
the boards that John suggests, but as finished rugged units including
display, antenna, batteries and charger, they may still have apeal.
The other thing covered that makes the message longer than I
want to post is a copy of an old reply to another poster in which I
try to remember enough about how GPS works in detail, with the object
of convincing the reader that there are better home brew projects upon
which to spend one's time. It could serve to try to convince you that
waiting for the $295 Magellan board is the way to go.
Bill Freeman, KE1G, waf@zk3.dec.com
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Date: Mon, 28 Feb 1994 16:37:23 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!wa4mei.ping.com!ke4zv!gary@network.ucsd.edu
Subject: Portable Oscar 13 Station?
To: ham-space@ucsd.edu
In article <1994Feb27.212556.8284@arrl.org> zlau@arrl.org (Zack Lau (KH6CP)) writes:
>
>I tried Mode S, 6 watts to a 5.5 ft boom 436 MHz
>yagi and a 2 ft. dish with a 2.4 GHz feed, but
>only made 6 contacts in 3 hours (1 hr/day).
>
>Problem was, several stations had trouble hearing
>my signal, even though it sounded fine to me.
>I could sometimes hear myself clearly running
>6 dB less power (1.5 watts).
Hey, that's good. The problem's not on your end. The
problem is that most mode S stations are deaf, most
mode B too if the truth be known.
>Should I try Mode B or work on my 436 antenna?
>
>I prefer small antennas I can stick in my car
>without taking apart. Makes a big difference
>when the weather changes for the worse....
The sad fact is that most Oscar users will have
trouble copying you if your signal is much weaker
than the beacon. If you can muster about 100 watts
ERP uplink on 436, a lot more stations will respond
to you. Also there's a lot more activity on mode B,
and some of those stations have impressive receiving
setups (ZRO 8 or better) and will have little trouble
copying your low power uplink.
I had a nice long SSB chat with a group uplinking to
Oscar 10 from Antarctia who were using only 5 watts
and a short beam. (This was before AO10 went sour.)
They'd been calling for days with no response. After I
built a pileup for them, they made a bunch of contacts.
Of course I was using four stacked 424B Long Boomers
with a good mast mounted preamp at the time and they
came booming in on my receiver. Most other stations
had been tuning right past them without noticing they
were there.
When I operate portable, I use a short helix for uplink,
and a 100 watt Mirage amp. I can make enough uplink power
to be heard clearly by most stations, and can turn down
the wick with the better stations. The problem on mode
B is receiving with a small antenna. It limits you to
working only the stronger stations. Your mode S receive
setup sounds really hot. I can't claim that kind of
performance, and I have a 4 foot dish at the home
station. (I obviously need a better LNA.)
Gary
--
Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary
534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244 | |
------------------------------
Date: 28 Feb 1994 20:34:03 -0500
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!howland.reston.ans.net!news.ans.net!hp81.prod.aol.net!rmg01.prod.aol.net!not-for-mail@network.ucsd.edu
Subject: Satellite FAQ answers (long)
To: ham-space@ucsd.edu
Excellent, excellent, excellent! A great asset to the satellite shy users out
there!
73 for now.... c u on the shortwaves
Terry Stader - KA8SCP
America Online Ham Radio Club Host
Internet: tstader@aol.com (files <28K) or
p00489@psilink.com ( files >28K)
KA8SCP@WA1PHY.#EMA.MA.USA.NOAM
ka8scp@ka8scp.ampr.org [44.56.4.82] Mac
ka8scp-1@ka8scp-1.ampr.org [44.56.4.120] DOS Clone
(they're BOTH pc's!)
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End of Ham-Space Digest V94 #45
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