Re: Radio Telemetry

Jon Slaughter wrote:
Are there any devices that do radio telemetry of up to a mile that are very small and use little power? (I'm not familiar with this area at all)

Basically I want to do a project while revolves around getting the position of a moving object(moves < 50mphs) over a distance of several hundred meters(but maybe up to 1 mile or so in extreme conditions). I can attach a device to the object but it needs to be small as possible(except possibly the antenna).

My method was going to use triangulation by having 2 other fixed devices that listen to a signal produced by a device on the remote object. Essentially they would listen for the device sending a pulse wave of known freqency and calculate the dopler shift(well, just the time it takes to get the next pulse). I'm not sure if this is very accurate though as I need to know precisely where the object is(up to inches atleast but cm or mm is much better).

I think the method probably isn't great due to the low speeds involved but I'm not sure. I think that the object will end up showing no movement at all due to round off errors and such.

This is basically like wildlife telemetry where I want to get the position of an animal very precisely and then plot its movements. I'm just not sure if what I want is practical and not to sure about where to start. Are there IC's that essentially do what I want?

Oh, I was thinking that I could have multiple fixed "observation" devices that could monitor the signal then in the software I could compute some average triangulation from them all. I'm not so woried about the fixed devices as the can be as large as needed(well, practically only several pounds or so).

I was also thinking that maybe RFID might work too but I have no idea as I don't know anything about it(not sure the distances it works over but I doubt it can be used for what I want). Lasers for accuracy are ofcourse out of the question. I'd also have to worry about atmospheric effects too but I suppose I can worry about efficiency once I get on the right track.

Oh, and I think GPS is probably out of the question too because of the accuracy I need and because I really need something that is virtually fail proof(not going to cause problems when a cloud goes by or something like that or the object goes under a tree).

Any Ideas?

Thanks,
Jon



One approach is to use a LORAN-type position location system. Over a fairly small area (i.e., not the entire globe) it may offer some possibilities. You don't specify the required accuracy so you'll have to evaluate it yourself. Basically, it involves defining hyperbolae based on signals from pairs of transmitting stations. Interesting math if you want three dimensions.

There is a lot of LORAN info available on the web that might help you.

But depending on your accuracy requirements and the area over which you would be tracking, I think you should expect some enormous challenges.

Chuck


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