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Posted: Sat Mar 08, 2014 2:01 am
by Eric
I saw the PiFM project and I am truly intrigued. I was thinking about capturing some audio via my SDR's (such as basic doorbell, old style garage door etc) and play it back via the Pi on the appropriate Frequency. Anyone try this by chance?

Re: Pi FM

Posted: Thu Apr 03, 2014 6:41 am
by jcims
Hey Eric!

It's not good enough that i spam the heck out of your youtube channel, lol!

I have tinkered with PiFM a bit. It doesn't compete quality-wise with purpose built transmitters, but it certainly gets the job done. However, if you fire up your rtl while you're running it and surf up the spectrum from your intended transmission frequency, you'll laugh at the insane number of harmonics that it generates. For example, I've found that transmitting on ~207-208MHz creates so much splatter that it will jam CDMA cell phones within 5-6 feet of the device.

I do think it would be fun to use as an ISM band transmitter/signal cloner and am thinking of trying to use it to create a DIY metal detector, but it would need some good lowpass/bandpass filtering to be good for long term FM transmission.

That said, i'd still give it a go, it's pretty fun!

Re: Pi FM

Posted: Thu Apr 03, 2014 4:36 pm
by Eric
Heya! No it's good to have you here. I made the forum so people with like minds could share some info and also be able to find it sometime later without it being lost in the comment heap. I'll be honest, I'm a forum nerd. I love them and how fast ideas can be shared and recorded for all time. They just don't fit in terribly well with the social media model today :)

Thanks for the input on the PiFM. I totally expected there to be harmonics just blasting out all over the place haha. It's interesting to hear that's exactly what you saw. The fact the splatter is bad enough to jam cells is kinda funny.

The metal detector is a super cool idea. That is just plain neat. The advancements lately in DIY electronics have been amazing- what new applications people are using them for- is simply stunning!

I really need to make some time to just play with the Pi. I haven't used it at all other than the initial setup. Time to play with it I think :)