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I recently bought an AM radio transmitter/receiver from eBay.

It was only after I bought it, however, that I noticed that the frequency was 315/433 MHz. I live in the UK so only 433 MHz would be legal for my use. At the bottom of the eBay page it says that I can set the frequency. How do I go about doing so. Thanks in advance, I've never used radio communications before.

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The way that is written, I believe the Ebay seller just copied the product description from the actual manufacturer. The way to get a different frequency would be to contact the manufacturer and order parts built with different components that give the frequency you choose. –  The Photon Oct 29 '12 at 16:08
    
Normally I'd look in the datasheet, but I can't find an English one for this (I think it's an Aoke AK-R03A based on that image) –  pjc50 Oct 29 '12 at 16:08
    
Since the Ebay seller lists the part as a "433 MHz" module, they have probably done just that, and ordered the part configured for 433 MHz. But of course, on Ebay you never really know what you're going to get. –  The Photon Oct 29 '12 at 16:09
    
Aaaah. On the transmitter, there's a crystal that says 315.000 on it. I guess I'm going to have to send this thing back? –  user15682 Oct 29 '12 at 16:13
    
At GBP 1 for the product and GBP 2 for S&H, I'm thinking either you or (if you're lucky) the Ebay guy is going to end up eating the cost of the part you have, and if you're lucky you'll get a new part with a configuration that matches the advertised product description. –  The Photon Oct 29 '12 at 16:28
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2 Answers

To change the transmit frequency you'll have to change the SAW resonator as well as some component values, not really what I'd call practical. The receiver frequency is fairly easy to adjust, turning out the glued in inductor reduces the frequency, I was able to turn mine down to 405MHz by completely turning out the iron screw.

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You cannot easily change the carrier freq. as this simple design uses a Narrowband SAW filter.

Ironically the photo shows the part for a P315 (MHz) part yet says it is advertised as a 433 MHz device, so the photo does not seem to represent the exact part. If you buy another SAW resonator or another package, you may be able to change it.

Model Nom. f Insertion Loss   Quality factors     Package

              .       (MHz) (dB)  Q, Unloaded Q 50Ω load  


 p315 315.000 ≤ 2.0   ≥12,000     ≥2,000  .      TO-39,F11 TO-39, F11

They forgot ( I believe) to tell you how to specify the Tx frequency on your order. The Rx is wide band.

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