[Az-Geocaching] Amateur Beacon / GeoCache..

Fred Coe listserv@azgeocaching.com
Thu, 18 Apr 2002 18:26:16 -0700


Howdy,

I've been on the road to Douglas and Sierra Vista this week, and just
getting caught up on the mail.

It sounds interesting, especially since I found out (today!) that I might
end up being the custodian of some rather sophisticated doppler RDF
equipment.  It's purpose is to track down interference from Mexico, but I'll
have to calibrate, test, and learn how to use it sometime....

If I read and understand some of the posts on this topic correctly (and as I
type this, I'm tired, dirty, and mildly sunburned--hmmm, if its fun
geocaching, why isn't it fun at work?, but my mind wanders...).   The
coordinates given will lead to a jumping off spot, where you will RDF to the
location of the cache.

Potential locations will be your challenge.  Most mountain tops with
relatively easy access are already littered with various RF emitters which
will make zeroing in on the TX in question a challenge.  Mt. Lemmon, and
Heliograph have enough intermod to wipe out my Bendix-King XCVRs about 1/4
mile from the respective summits.  I imagine South Mountain in PHX is worse.
150 mW will have trouble competing with even the 5th order intermod at those
sites, particularly if a consumer scanner or typical compact amateur radio
HT is used for RX.  Since this maybe some our geocacher's first experience
with T-Hunting I recommend you put it in a relatively RF quiet area so it
can be found using a handheld scanner and the body shielding technique.

I also recommend that you include some simple T-Hunting techniques (or at
least references) on the cache page.  And/or consider holding a geocache
get-together before the cache is actually deployed to demonstrate some of
the techniques to help some of the folks not familiar with T-Hunting get the
hang of things.

I'd be interested in hearing about charge control, power, and battery
management for a solar power system on this small a  scale--then again it's
so small it may not matter.

This cache sounds like a great way to combine interests, and maybe encourage
some geocachers to consider amateur radio as another hobby, and hams to
consider geocaching.

--Fred
WA0RTO
Team Boulder Creek

Glossary
(added after I re-read the message an noticed the techno-babble):

doppler RDF: Radio Direction Finding using doppler shift between antennas
RF emitters:  Radio Frequency transmitters
TX:  Transmitter or transmit (depends on context)
Intermod: short for intermodulation distortion, what happens in a RX when
you mix different TX frequencies together
XCVR: the morse code abbrevation for transceiver
mW: milliwatt
HT: handitalkie-handheld xcvr
RX: Receiver or receive (depends on context)
T-Hunting:  Transmitter Hunting

es 73  de WA0RTO  sk

----- Original Message -----
From: "C. Sullivan" <feedle@feedle.net>
To: <listserv@azgeocaching.com>
Sent: Tuesday, April 16, 2002 6:09 PM
Subject: [Az-Geocaching] Amateur Beacon / GeoCache..


> It's about to happen: a GeoCache that can be found not only by GPS, but by
> radio direction-finding.
>
> I recently constructed a small QRP 2 meter CW beacon inside the bottom of
> a quart-size paint can.  It has a small solar panel and two AA NiCd cells
> for power.  It is capable of transmitting a 100-character message every
> five minutes.  My initial tests show it has about a 45mW output.. but
> beefing that up to around 150mW should be trivial (one good transistor can
> do wonders).
>
> I've given it a lot of thought, and I've decided that I want this little
> "rabbit" to be my first GeoCache.  The only problem is, I can't think of a
> really good place to put it.  So, here's my challenge.
>
> If somebody out there who is a ham (or other radio hobbyist) can find me a
> good mountaintop site to hide a GeoCache, preferably somewhere where a
> 100mW signal can be heard for enough of a distance to be
> challenging / interesting to RDF enthusiasts, and also an interesting
> destination for the GPS-equipped.
>
> Anyone have any thoughts?
>
> Feedle (aka Chris KD6COS)
>
>
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