Are the ubiquitous and incredibly cheap FRS radios of any use in ham radio?
I have always been really curious about that. But a Google search turns up very little in the way of hams hacking FRS radios for amateur radio uses. Well, I'm working with Dr. Cool (who prefers to remain anonymous) to do just that. We got some Cobra Microtalk FRS radios for just $2.50 after rebate. Cool opened them up to see just what's inside.
Turns out that the PLL chip is clearly marked (it's the MCD2926) and the datasheet is available. Reprogramming the PLL for different freqs is pretty simple. I even created a spreadsheet that lets you plug in a frequency and it comes up with the various command values you need to send to the chip. So theoretically, a guy should be able to push these dudes down into the ham bands by 1) retuning the VCO that's in the radio to go down about 20 MHz (from the FRS allocations, into the 430 - 450 MHz ham band) and 2) hijacking the control pins to the PLL to tell it where to go. Maybe just the first would actually get you into the ham band.
The other thing I'd like to do is to replace the VCO that's on the radio with one of the Maxim VCO parts (MAX2605/2606/2607/2608/2609, costing about $1 each). That way you'd get a nice programmable oscillator for the range of the particular VCO you select. Seems like it would be great for a small bench-top programmable oscillator or for the basis of a cheap beacon for 50/144/222/432 MHz.
We're going to keep hacking at these things, so I'll keep you posted.
[Here's the data stream being sent to the PLL chip. Won't be hard to program a little PIC processor to send that out.]
73 de W9HQ