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Making an FM radio digital tuner

Hi,

I'd like to build a clock radio as a hobbyist project. My ideas are to get a Galleon EM2S receiver for WWVB time signals, hook it up to a PIC microcontroller, and also have the PIC control a digitally tuned FM receiver. (Yes, I'm determined to spend hundreds of dollars, dozens of hours, and risk total failure, rather than buy a $50 Sony "atomic" clock/radio. That's what hobbies are for, right?)

My question is, can anyone advise me on how to digitally tune a radio? I've found lots of OEM, digitally tuned radio modules, and I'd love to get my hands on one. But the manufacturers only deal with OEMs, and I haven't seen anyone like Jameco or Digikey selling individual units.

Alternatively, there's several FM radio kits I could buy, but they are tuned by variable capacitors. Is there a way to replace that with digital electronics?

Finally, I could buy a cheapo pocket radio, but it's already got an LCD. I doubt my ability to hack into something like that and control it.

Any suggestions?

Thanks, Bob Alexander

Reply to
realexander
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I think it would be easier to have a D/A output from the PIC [or AVR or Freescale or ARM or 8051...] microcontroller to control the DC voltage to a couple of varactor diodes to tune the RF input and local-oscillator stages of an off-the-shelf radio (presumably the kit the OP mentioned).

So let me see if I understand this: The PIC [brand name of microcontroller] reads WWVB time signals to display the time, and also controls the station the (Broadcast?) FM radio is tuned to? Not that there's a problem doing it. I suppose you could even make it a 'programmable' radio that would turn on and off and change the station at preset times of day, similar to a VCR.

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Reply to
Ben Bradley

You want a phase-locked loop synthesiser for the receiver local oscillator. Nat Semi makes suitable chips, but you will have to design the VCO and loop filter. If you haven't done this sort of thing before you are in for quite a lot of work.

Leon

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Leon Heller, G1HSM
http://www.geocities.com/leon_heller
Reply to
Leon Heller

Yep, decent choice, and should be useful at the end.

I had a look inside a Denon AM/FM tuner and found an LM7000 series chip.

The MPU has a Z80 core.

What you could do is get a similar radio and remove the MPU core and wire your own board to the I/O connections. You then have to write your own application to run the show, but all the fiddly bits are done for you.

Note that radios are usually hi-integration items, so some of the cheaper radios merge the MPU with the radio section. You might not want to spend cash on an expensive tuner where they might be separate.

It is easy, just get the data sheet for the chip in use.

Not much point, just buy an FM tuner.

Note that most components are surface mount so buying an existing product to hack is cheaper than getting a board made and populated.

I can send you the reverse-engineered cct of my TU1500. Not guaranteed error free, but it will show you what kind of things surround the MPU.

Reply to
Kryten

There was an article in Wireless(Electronics?) World a few years back, with schematic and instructions to make a fully digital radio. It had a broadband simple tuner front end and everything after that was done in software. Perhaps this may be worth a look before you go too far into re-inventing the wheel :

Reply to
Bill Bailley

I vaguely recall some of philipses radio parts being online orderable. For more giggles, a slightly faster processor would let you do wwvb in softweare.

Reply to
Ian Stirling

Hi Ian,

If you know where to order those Phillips parts, I'd love to hear it. My multiple seaches have turned up nothing.

in

I'm not sure I could survive all those giggles. :-) Are you referring to hooking up an antenna to an A/D, then to a DSP or something? That would probably require something a lot faster than a PIC, not just "slightly" faster. Or did you have something less ambitious in mind?

- Bob

Reply to
realexander

to get a Galleon EM2S receiver for WWVB time signals, hook it up to a PIC

of

radio?

to

I

units.

orderable.

in

If you can get the levels of the 60 KHz OK for the processor, wouldn't a simple 'hardware assist' make the software easier? A divide by 6 or

10 would get down to 10 or 6 KHz which shouldn't be too difficult to process. GG
Reply to
Glenn Gundlach

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