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Radio Cache


mighty79
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Ok, I am considering cache which is unique for this area. What I want to do is to take a simple FM transmitter that you would purchase at say RadioShack and connect it to a solar cell. I would then place the transmitter with the cache. The coordinates would only get you within radio range of the geo cache. To find the geo cache you would have to triangulate its position with a radio receiver. Not to mention that in order to do this you would have to know how to do it as well which would entail a little research.

 

1. What would the hidden pitfalls of this be?

2. How would I classify this cache?

3. Any suggestions on entering the coordinates?

4. Has anyone else attempted something like this?

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This is a Radio Direction Finding (RDF) exercise called Fox Hunting and is quite popular in the amateur radio community.

 

Info on building the fox (transmitter) and the directional antennas needed to find it can be found at http://www.homingin.com/index.html

 

Fox-hunting is usually a hiking exercise, but in open areas, most notably in California, it is done with cars and called T-hunting or Transmitter Hunting. More on that at http://www.homingin.com/SCalStyle.html

 

There is a nexus with geocaching: T-hunters have become very sophisticated at finding dastardly hiding places. With the right combination of location and antenna, they make it difficult for hunters to get reliable bearings. Like a ventriloquist, a good hider can make the signal appear to be coming from some other location. With careful planning (and a little luck), the signal's characteristics can cause the hunters to approach the transmitter from the most difficult direction, with impassable roads or other obstructions, even though the T may be easily accessible via other routes. Perhaps the hider will camouflage the setup so well that the hunters won't find the transmitter unless they literally trip over it.

 

To integrate geocaching and fox-hunting you might consider a 2-stage multi, where the first stage is a large ammo can with a receiver and directional antenna. When a cacher finds it he uses the receiver to find the fox, the second stage. Receivers are cheap and the directional antenna even cheaper... you can make a directional antenna from an old BBQ grill or even a stick and some pieces of a broken metal tape measure!

 

You can discuss RDF and any other radio topic on my website forum, W4AGA.com if you need help.

 

I have seen talk over the years in these forums about RDF Caches but don't know of any that have gotten past the talk stage.

 

73 de W4AGA

Edited by TheAlabamaRambler
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What would you broadcast with that FM transmitter? You would have to transmit some kind of audible sound instead of just a carrier...so someone could hear it to triangulate on. However, To triangulate, you might need some kind of directional antenna....a simple handheld loop, beam, quad...but that might require some tech background to build and connect it to a radio.

 

Go search for caches by KEYWORD = RADIO. You might find some other caches there like the one below.

 

http://www.geocaching.com/seek/cache_detai...e3-f5cda97c08da

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This is a Radio Direction Finding (RDF) exercise called Fox Hunting and is quite popular in the amateur radio community.

 

Info on building the fox (transmitter) and the directional antennas needed to find it can be found at http://www.homingin.com/index.html

 

Fox-hunting is usually a hiking exercise, but in open areas, most notably in California, it is done with cars and called T-hunting or Transmitter Hunting. More on that at http://www.homingin.com/SCalStyle.html

 

There is a nexus with geocaching: T-hunters have become very sophisticated at finding dastardly hiding places. With the right combination of location and antenna, they make it difficult for hunters to get reliable bearings. Like a ventriloquist, a good hider can make the signal appear to be coming from some other location. With careful planning (and a little luck), the signal's characteristics can cause the hunters to approach the transmitter from the most difficult direction, with impassable roads or other obstructions, even though the T may be easily accessible via other routes. Perhaps the hider will camouflage the setup so well that the hunters won't find the transmitter unless they literally trip over it.

 

You can discuss RDF and any other radio topic on my website forum, W4AGA.com if you need help.

 

I have seen talk over the years in these forums about RDF Caches but don't know of any that have gotten past the talk stage.

 

73 de W4AGA

Wow! Your post about RDF ham events brings back memories! A gazillion years ago, in the 1950s and 1960s, I usetda do ham RDF fox hunts and also ham radio Field Days, which often had local RDF contests as well. Memories...!

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1. What would the hidden pitfalls of this be?

Very few people would hunt for it; danger of someone stealing your transmitter.

2. How would I classify this cache?

Mystery/Unknown

3. Any suggestions on entering the coordinates?

Not from me, sorry.

4. Has anyone else attempted something like this?

Yes, I've read about similar caches here in the forums... a search should turn them up

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Ok, I am considering cache which is unique for this area. What I want to do is to take a simple FM transmitter that you would purchase at say RadioShack and connect it to a solar cell. I would then place the transmitter with the cache. The coordinates would only get you within radio range of the geo cache. To find the geo cache you would have to triangulate its position with a radio receiver. Not to mention that in order to do this you would have to know how to do it as well which would entail a little research.

 

1. What would the hidden pitfalls of this be?

2. How would I classify this cache?

3. Any suggestions on entering the coordinates?

4. Has anyone else attempted something like this?

 

As far as no. 4, sort of. Here you go, Geocaching Radio Fun near Rochester, N.Y. And the cache description gives the waypoint for the cache he got the idea from, in Alabama. Sounds interesting, but I didn't get a chance to try it when I was sort of nearby.

 

Oh, the FM transmitter for this cache is on the cache owners property.

Edited by TheWhiteUrkel
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This is a Radio Direction Finding (RDF) exercise called Fox Hunting and is quite popular in the amateur radio community.

 

Info on building the fox (transmitter) and the directional antennas needed to find it can be found at http://www.homingin.com/index.html

 

Fox-hunting is usually a hiking exercise, but in open areas, most notably in California, it is done with cars and called T-hunting or Transmitter Hunting. More on that at http://www.homingin.com/SCalStyle.html

 

There is a nexus with geocaching: T-hunters have become very sophisticated at finding dastardly hiding places. With the right combination of location and antenna, they make it difficult for hunters to get reliable bearings. Like a ventriloquist, a good hider can make the signal appear to be coming from some other location. With careful planning (and a little luck), the signal's characteristics can cause the hunters to approach the transmitter from the most difficult direction, with impassable roads or other obstructions, even though the T may be easily accessible via other routes. Perhaps the hider will camouflage the setup so well that the hunters won't find the transmitter unless they literally trip over it.

 

To integrate geocaching and fox-hunting you might consider a 2-stage multi, where the first stage is a large ammo can with a receiver and directional antenna. When a cacher finds it he uses the receiver to find the fox, the second stage. Receivers are cheap and the directional antenna even cheaper... you can make a directional antenna from an old BBQ grill or even a stick and some pieces of a broken metal tape measure!

 

You can discuss RDF and any other radio topic on my website forum, W4AGA.com if you need help.

 

I have seen talk over the years in these forums about RDF Caches but don't know of any that have gotten past the talk stage.

 

73 de W4AGA

 

Try this one.

http://www.geocaching.com/seek/cache_detai...b6-13865d8530a5

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You would not need to transmit coordinates. just sending beeps would be all that is required. As the cacher get closer the beep will be stonger.

If you place the cache close to your home you clould use a large rechargable gell cell battery to run the radio, as long the radio is running on low power a gell cell could last several weeks. A solar would help to keep the battery charged

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1. What would the hidden pitfalls of this be?

Interference with licensed radio or TV transmissions which could conceivably result in hefty fines in the very unlikely event the FCC got involved.

 

The cheaper the transmitter the more likely it is to produce unwanted spurs and harmonics.

 

Using the 'toy" transmitters as intended, meaning intermittent, short term operations without modification, makes such interference potential negligible or at least manageable.

 

Modifying the transmitter to use a different battery and turning it on 24/7 vastly increases the potential for harmful interference. Modifying a part 15 device in any way voids its part 15 certification.

 

A low power transmitter can cause interference for many miles to a base station receiver. I find them very frequently in the course of my job... most that I find are less than 1 watt power and cause problems to multiple State Police sites within 30 mile radius. Some interference sources are not even intended to radiate useful RF at all, such as sat TV converter boxes and cable TV cables and connectors, and I have found these types interfering over a mile from sites. Your "toy" transmitter would fall somewhere in between.

 

24/7 transmitters are particularly troublesome even if operating properly. Among other things, they provide a constant source of one of the two or three or more signals needed to produce intermod products. With a constant source, IM problems occur with much more frequency.

 

So anyway, go for it... Iowa might be a nice place to visit on the company dole. :laughing:

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:anibad: Here is my radio cache GC18KQN called "Counting Station"

 

The cacher has to read the description and figure out where the radio station is. Then he has to drive/go there and search the FM band for mysterious sounds and countings like ECHO ZERO FIFE ZERO... :D which gives out the final

 

Works fine and I have super responses!

But... it's forbidden by law :D

 

The radio transmitter is self build by the "Mini FM" group, Berlin/Germany (pritae radio) and works up to 100 meter!!!!

It's power supplyed by a USB port. The PC is alway on and the Windows Media Player runs the wav file in loop.

 

Happy hunting,

Martin

Edited by weinema
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I build radio tracking transmitters for amateur rocketry use. They work on the 433 / 434 mhz or 869 / 915 Mhz ISM bands, so are OK to use in most countries. Hard coding a beacon to send its co-ords as a morse signal would be simple.

While the transmitters and Yagi-Uda antenna are quite cheap to build, the receiver is somewhat more expensive. My Icom IC-R20 currently retails for about £290!! :unsure:

 

P.

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I build radio tracking transmitters for amateur rocketry use. They work on the 433 / 434 mhz or 869 / 915 Mhz ISM bands, so are OK to use in most countries. Hard coding a beacon to send its co-ords as a morse signal would be simple.

While the transmitters and Yagi-Uda antenna are quite cheap to build, the receiver is somewhat more expensive. My Icom IC-R20 currently retails for about £290!! :)

 

P.

 

I think the idea is pretty good, but it really wouldn't work well on non-public broadcast bands.

 

The big advantage of using a ham band is that, provided it is controlled by a licensed Amateur, it is well legal.

 

The big disadvantage is that receivers are a not as common amongst the general public as are broadcast receivers.

 

I only raise the interference issue because it is something seldom considered by people who do these things and could potentially cause quite a mess.

 

Unintentional interference is not at all uncommon and most sources I have found so far are devices that do not intentionally transmit any energy in the band which they are interfering with. The users of the offending devices seldom know they are causing a problem until I and a State man knock on their door.

 

I tracked down three State Police interference sources in the last week.

 

Tracking these sources takes a lot of time and if we were to bill my time to the source owners, (this has never been done to my knowledge, but COULD be if someone wanted to "push it") the charges would be a couple of thousand dollars each incident, typically.

 

thinking it through from the potential interference standpoint, I would be more scared of a transmitter in the 432 or 869 bands than I would of the standard broadcast bands. Second harmonic of 432 and sideband noise of 869 could EASILY land on public safety frequencies.

 

It would be a BEST PRACTICE to design this device so it would only transmit when someone is actively looking for the cache. That would make the interference risk negligible.

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Ok, I am considering cache which is unique for this area. What I want to do is to take a simple FM transmitter that you would purchase at say RadioShack and connect it to a solar cell. I would then place the transmitter with the cache. The coordinates would only get you within radio range of the geo cache. To find the geo cache you would have to triangulate its position with a radio receiver. Not to mention that in order to do this you would have to know how to do it as well which would entail a little research.

 

1. What would the hidden pitfalls of this be?

2. How would I classify this cache?

3. Any suggestions on entering the coordinates?

4. Has anyone else attempted something like this?

 

While AlabamaRambler was right on most counts, Be aware that many Frecs. are tabo with the FCC. Others are limited to Ham or other organizations.

Otherwise, it could be fun.

'kc7pgt'

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An other problem of very cheap or selfmade FM trasmitter is that the frequency is not stable :-(

Depending on the power supply voltage and/or if you just "touch" your self made transmitter

the frequency sometimes changes 1 or more MhZ :-/

 

My self made transmitter does so.

On time the frequency raises and had interferrences with a radio station.

An other time it drops and was in the police range :-} *uaauuaauuaaa*badidea*

 

Martin

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Here is an idea I was looking into for a cache that might workfor you, a friend was a real estate agent that had one of those 'talking house' set ups. I was going to use that and broadcast the coods for a multi. I bet you could find one on ebay. Heck eveything else is on there.

I have done a few clicks of research to try to find these and information on them but was largely unsuccessful. The people who want to sell them outright spend a lot of bandwidth on hype and not prices or useful information like specs and legalities.

 

My primary question: Do these units require a license?

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An other problem of very cheap or selfmade FM trasmitter is that the frequency is not stable :-(

Depending on the power supply voltage and/or if you just "touch" your self made transmitter

the frequency sometimes changes 1 or more MhZ :-/

 

My self made transmitter does so.

On time the frequency raises and had interferrences with a radio station.

An other time it drops and was in the police range :-} *uaauuaauuaaa*badidea*

 

Martin

This is VERY common on cheap transmitters.

 

A possible unit to use for this type of cache that would not experience this problem is any of the many "FM modulator" adapters for Ipod® type units. Most of these have several programmable frequencies (not tunable) so a clear one could be selected which SHOULD (operative word) remain stable.

 

These units are SO short range that sometimes they won't even "make the trip" the three feet or so from the car dash to the FM whip outside.

 

I doubt that one of these, unmodified, would have much interference potential unless you placed it right IN the hot part of the antenna pattern of a receiving tower.

 

The cacher would have to get REAL close to the unit though.

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Ok, I am considering cache which is unique for this area. What I want to do is to take a simple FM transmitter that you would purchase at say RadioShack and connect it to a solar cell. I would then place the transmitter with the cache. The coordinates would only get you within radio range of the geo cache. To find the geo cache you would have to triangulate its position with a radio receiver. Not to mention that in order to do this you would have to know how to do it as well which would entail a little research.

 

1. What would the hidden pitfalls of this be?

2. How would I classify this cache?

3. Any suggestions on entering the coordinates?

4. Has anyone else attempted something like this?

 

While AlabamaRambler was right on most counts, Be aware that many Frecs. are tabo with the FCC. Others are limited to Ham or other organizations.

Otherwise, it could be fun.

'kc7pgt'

 

yes, the talking house TXers or the Ramsey items would be the safest bet. I am thinking of doing one here in AR good luck,

 

Eric

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Here is an idea I was looking into for a cache that might workfor you, a friend was a real estate agent that had one of those 'talking house' set ups. I was going to use that and broadcast the coods for a multi. I bet you could find one on ebay. Heck eveything else is on there.

I have done a few clicks of research to try to find these and information on them but was largely unsuccessful. The people who want to sell them outright spend a lot of bandwidth on hype and not prices or useful information like specs and legalities.

 

My primary question: Do these units require a license?

 

the talking house units along with the ramsey units are FCC typed, as long as they are not moded

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Here is an idea I was looking into for a cache that might workfor you, a friend was a real estate agent that had one of those 'talking house' set ups. I was going to use that and broadcast the coods for a multi. I bet you could find one on ebay. Heck eveything else is on there.

I have done a few clicks of research to try to find these and information on them but was largely unsuccessful. The people who want to sell them outright spend a lot of bandwidth on hype and not prices or useful information like specs and legalities.

 

My primary question: Do these units require a license?

 

the talking house units along with the ramsey units are FCC typed, as long as they are not moded

 

also, no lic requird, tx on FM 88-108. another option that I was thinking are the FRS freqs, but this option is more tech and may not be legal

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The simplest solution has already been eluded to. Use a simple fm transmitter from walmart, radio shack etc etc. They are low power, fcc sanctioned and pretty reliable. Connect it to am mp3 player or cd player and you can repeat an mp3 file (that you recorded) to provide coords in a multi. Most have a range good enough to drive to and receive the signal. I've done one and my Pops has one thats been live for years without problems.

 

Pretty basic stuff and you don't have any regulatory crap to worry about.

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1. What would the hidden pitfalls of this be?

Interference with licensed radio or TV transmissions which could conceivably result in hefty fines in the very unlikely event the FCC got involved....

 

The low power FM Transmitters you can buy over the counter at radio shack have the FCC thumbs up. The worst I've encountered is truckers using the same 'dead space' as mine. For some reason their transmitter is always stronger and I have to listen to their Romance Audio Book while we pass each other.

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1. What would the hidden pitfalls of this be?

Interference with licensed radio or TV transmissions which could conceivably result in hefty fines in the very unlikely event the FCC got involved....

 

The low power FM Transmitters you can buy over the counter at radio shack have the FCC thumbs up. The worst I've encountered is truckers using the same 'dead space' as mine. For some reason their transmitter is always stronger and I have to listen to their Romance Audio Book while we pass each other.

The fact that the transmitters have the "FCC thumbs up" does not in any way exempt them from liability for interference.

 

FCC regs part 15 under which these devices are sanctioned requires the devices to accept any interference even if it results in unacceptable operation and that they must not cause interference to licensed radio services.

 

Interference potential exists with any and all electrical devices. My advice is not "don't do it" but simply be careful and understand that the potential exists. i would be EXTREMELY careful about placing such a cache within a short distance of a commercial tower of any kind (such as a cell tower). I have had a site trashed by a cable TV leak two blocks from a tower. The cable was radiating much less energy than part 15 limits on FM broadcast.

 

Fines are VERY UNLIKELY as long as the cache owner fully cooperates in any interference investigation that might result, but the possibility DOES exist- which is one "hidden pitfall" that the OP asked about.

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