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" To: 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) > > > _______________________________________________ > Az-Geocaching mailing list > listserv@azgeocaching.com > http://listserv.azgeocaching.com/mailman/listinfo/az-geocaching > > Arizona's Geocaching Resource > http://www.azgeocaching.com >