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27MHz antenna question

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I'm new here, so 'hello'

I'm not an R/C person, but I may have a use for an an el cheapo 27MHz set-up.

I want to make a link, over only about 50 feet, but it has to be wireless.

I have considered an optical link, but at the moment I'm still at the stage where questions are being asked.

I will attempt to make this as coherent as I can:

The receiver is not a normal R/C receiver; it's a quite different electronic device which I need to turn ON

on demand ( so a timer /PIC is not much help here ). The device has to be battery-powered

and the battery will be (hopefully ) kept charged by a small solar panel. Ergo , I need a method

of turning this device ON using some kind of receiver which draws little, or no, current.

Now, there is the unpowered field-strength meter, which can generate a few hundred

milli-volts when close to the transmitter. I have a home-made transmitter which is around

100mW AFAIK ( it's very old and uses a design of Mike Newell circa 1970 : anyone old enough to

remember him?)

So, using this transmitter, I want to send a signal to a tuned-circuit 50 feet away. Can I get enough response

from an unpowered tuned circuit to 'trip' a second circuit ( which will be battery-powered ) into life?

The first circuit could conceivably be powered if it draws only micro-amps.

Does anyone know if this trick has been done before ( I've not seen anything on Google ).

Or can you make suggestions as to how it could be accomplished.



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The RF industry does not have much to offer in the way of modern 27MHz solutions (it's a band that is mostly used by cheap Hong Kong toys). But there are plenty of UHF band RF chips for remote control and data applications that have low power features. For example, http://www.micrel.com/page.do?page=/product-info/products/micrf219a.jsp . But if you need to stick with 27MHz then I suppose you could take a trip to the toy store and cannibalize their $10 R/C cars for parts.

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I made a paging alarm for my car back in the 80's that used 27Mhz. The receiver would only turn on for 1/4 second every 10 seconds to save power. When the correct coded signal was received it would spring into life and the LED's and beeper would sound.


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