Simple FM low power UHF transmitter circuit

Question

I want to build an low power transceiver on 33cm or 23cm (or 2 meters, but not recommended because of all the other activity interfering with my stuff) I would like to use FM and just have enough power for the nearby block to receive, kind of like a FRS radio but maybe even less power.

Are there any very simple circuits out there that will allow me to do this? I am thinking something really simple like the micro power FM broadcast transmitters. I would like to be able to fit it into something close to handheld and the reason I don't want to use 70cm is because my half-duplex AllStar repeater link will cause desensitization on that band.

I will link this up with a Simplex AllStar node so I can transceive around the house.

Answer 1

Microwave design is often far from simple, since stuff starts to behave significantly differently from how it would at HF or even VHF. Parasitics and the like become a serious problem.

That said, there are two designs I know of off the top of my head:

There's this one based on the MAX2750 VCO. You'd need to vary the input into TUNE with the audio output, and you would get an frequency-modulated signal out of K1. It's for 13 cm though; I believe Maxim make an alternative part for the 23 cm band as well.

There's also PE1JPD's design which, while more complex, is a complete transceiver, and about as simple in terms of two-way communications at 1 GHz as you're going to get.