Mini FM Transmitter

I remember Pop-tronics had one using a tunnel diode that was very small. You could hide it under a penny.

How much range do you need? That sort of sets the limit on size.

At very short ranges, a one transistor design can work ok.

transmitter.

hands on?

Maxim have a stereo VCO chip that can be used as a stereo FM transmitter. They have an application note with the circuit. It's a very small chip though!

Fred.

in article snipped-for-privacy@news.xsall.nl, Wouter van Ooijen

I designed an SMT stereo transmitter around the Rohm BH1417F IC. I might also be able to come up with a PCB. The BH1417 series has a PLL that reduces frequency drift; the BA series drifts with temperature.

E-mail me for a copy of the schematic & etc. Jon

define GOOD. low frequency drift (no 'hand effect') rules out most

Kitsrus has some FM transmitter kits. (I sell most of them).

Wouter van Ooijen

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Mini-FM transmitters that are not crystal derived stable are useless since they cannot be received on the majority of modern FM tuners.

The Radio Shack unit is not half bad. Schematics on my website.

As long as there is a manual tuning adjustment on one or other of tx or rx, it CAN be received (though possibly not optimally) even on modern digital tuners. I have commercial CD/MP3-to-FM car adapters that work this way, and nary a crystal to be found.

Power supply generally more important. Modern transistors are so small that the battery will be bigger. Hell, the smallest cell (4mmdia*2 height) is the size of several transistors by itself.

'cannot' is probably a bit strong.

(50Khz spacing)

Go here

Hello,

Just came back from Walmart. They had one for about $20, four programmable channels which may even be PLL controlled because there was just a single button on it. Stereo, too. The whole thing was smaller than a cigarette pack.

Why build if they are this cheap?

Regards, Joerg