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Making an FM radio digital tuner

R

realexander

Jan 1, 1970
0
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
 
L

Leon Heller

Jan 1, 1970
0
realexander said:
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.

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
 
B

Ben Bradley

Jan 1, 1970
0
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.

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.
 
K

Kryten

Jan 1, 1970
0
realexander said:
Hi,

I'd like to build a clock radio as a hobbyist project.

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.

My question is, can anyone advise me on how to digitally tune a radio?

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

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.
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.

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.
 
B

Bill Bailley

Jan 1, 1970
0
realexander said:
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

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 :<) Sorry I cannot recall the issue date, but someone
here should be able to point you right.

Luck, and maybe we can call you Gunga Din ! You certainly are a better man
than me.
 
I

Ian Stirling

Jan 1, 1970
0
realexander said:
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.

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.
 
R

realexander

Jan 1, 1970
0
Hi Ian,

If you know where to order those Phillips parts, I'd love to hear it.
My multiple seaches have turned up nothing.
For more giggles, a slightly faster processor would let you do wwvb in
software.

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
 
G

Glenn Gundlach

Jan 1, 1970
0
to get a Galleon EM2S receiver for WWVB time signals, hook it up to a
PIC
units.

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.

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
 
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