RF using Propeller

aanrudolph2

Hi, all.

I've been having major issues getting a simple analog FM transceiver to work. Unfortunately for me, all those "modules" that people sell handle primarily digital data. I decided that since it was going to be near impossible for me to make my own analog FM transceiver, why not use a Propeller to attempt to make one. (If that fails, too, I may as well just buy something). Is there an easy way to wire up a Propeller so it can send and receive data through the airwaves? I'm looking for a schematic, if at all possible, and the final product must be quite compact. I'm not looking to transmit more than 30 meters or so. (I DO NOT want to buy any ICs or extra components above and beyond resistors, capacitors and/or inductors).

Aaron.

Leon

What about the regulations in your country? What you are proposing would be illegal in the UK.

Mike Green

There's a big difference between demonstrating that something's possible and creating something reliable, useful, and well-behaved.

You can certainly program a Propeller to generate RF at a variety of frequencies. After all, the video circuitry is designed to be able to produce a modulated video signal on the lower VHF channels complete with simple FM sound. Whether the signal will go more than a few feet depends a lot on what's connected to the Propeller (like a simple tank circuitry at a minimum). Video is pretty forgiving of frequency drift and noise and other distortions of the signal and, if you can receive a signal at all on channels 2, 3, or 4, the quality leaves much to be desired. None the less, it can be done ... sometimes / maybe.

There has been a thread on the Propeller forum on ways to make a Propeller-based receiver. You might go through that since many of the techniques can be used to produce a modulated signal as well as do demodulation.

You will be much much better off using special purpose (analog or mixed) ICs for frequency synthesis and up conversion. With very careful attention to noise, jitter, shielding, etc., you may be able to put together a mostly Propeller powered transceiver using the Propeller as a digital signal processor at IF frequencies and as a controller for the rest of the transceiver.

aanrudolph2

The thought was that I could use the Propeller's counter modules to generate the frequency. Can this be done?

Phil Pilgrim (PhiPi)

The counter outputs are laden with square-wave harmonics and spurious sidebands due to phase jitter. As such they are unsuitable for RF transmission. You'd be causing interference all over the place.

-Phil