DIY Radio

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I would like to build a little portable stereo FM radio, for site use, so it has to be robust, and this discounts most cheap commercial FM radios. I suppose I could just rebuild one I bought, but before I go down this route I would like to try DIY if possible.

So, I can use some of my various GCs for amps, I have speakers, but I would like to know if anyone has a schematic for a simple FM only tuner, or links to a manufacturer's chipset data sheets. Google, and even Sherlock comes up with nothing, and the old threads on this board are not really relevent.

Cheers
 
It would be really interesing to make DIY FM receiver!
I'm planing to do one myself. I need it on my motorcycle. Interested in participation?

I don't know what are your plans about the funcionality(stereo, presets, digital tuner, seek, etc.)? Please write some more about it.

I don't need any of those functions, except maybe digital tuner.

I think that TDA7000 is on of the FM receivers that are easy to built. But I think it requires some adjustments - and we don't want those, do we?

So, I'm asking other members: do you know any IC's for FM receiver that don't require too much external parts?

Regards,
DJG
 
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Joined 2002
Hi DJG

I'm basically looking for a stereo tuner, no display needed, and either a knob or up/down buttons for tuning.

I had a look at the Philips site for the TDA chips, the basic ones seem to be all mono, and the stereo ones seem to need some kind of control interface to get them to work:(
 
Jeah, I know! Stereo is very hard to achieve, because you need to have stereo decoder and that takes a lot of time and work to tune it up for optimal performance.
If you looked at TDA7000 datasheet you saw that it can be modified to have potenciometer for setting the frequency.
If my memory doesn't lie, I think that I once saw one IC similar to TDA7000 that was able to produce stereo sound. I think it was TDA7005, but I'm not sure.
 
Hey! Have you checked TEA5711? It's an AM/FM stereo receiver.
Too many external parts for me. Sorry. I will probably go for TDA7000 or TDA7010, because I want to put it in my pocket plug the earphones and listen while I'm driving.

Check it out and tell us if you are into DIY project.
 
Check the FM tuner in ETI (electronics today international) that ran years ago. They started with a HF module giving out the 10.7 MHz multiplex and builded a nice stereo decoder around it. Dates:

march 1987, april 1987, july 1987 and august 1990. (not sure if this is complete but it should be the most important section)

Velleman had a nice kit, don't know if they carry it still.
 
I found it!
A great combinaton of fm tuner TDA7021 and stereo decoder TDA7040. A perfect combination for DIY. It requires only one inductive element printed on PCB.
Check out the datasheet of TDA7021 - there is a complete schematic of TDA7021, Tda7040 and TDA7050 as phono amp.
 
if you are going to build an FM tuner

there are some pretty knowledgeable folks on the tuner newsgroup at Yahoo.

a Gallium Arsenide front end would be nice.

this is another project where a little DIY can go a very long way to a great sounding project. Unfortunately the test equipment is a little daunting for the beginner.
 
A tuner is probably two orders of magnitude more
difficult to design than an amp or preamp. There
are a whole lot of different considerations,
more exotic circuitry/parts, etc. It can be
done -- amateur radio DIYers do it all the time,
though most are interested in "grunt" fidelity,
not high quality music.

I'd strongly suggest that you buy an existing
tuner and modify it, starting with the stereo
decoder and analog circuitry. Dynaco FM-5
tuners are available and cheap. To get into
anything before (and including?) the detector,
you need to have at least an RF spectrum
analyzer.

The world of broadcast radio is about to go
digital and that's definitely out of the
realm of the DIYer. The good thing is that
they'll still be broadcasting analog.
 
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Joined 2003
Tuners are much harder to make than anything else. that's why you can't find many designs. Worse, you need test gear and experience to align their IF strip. I understand the theory of how to align an align an IF strip, but I've never done it for real.

That's the bad news. The good news is that a stereo decoder shouldn't be nearly as difficult to make or align. I am currently mulling over some thoughts about a digital phase-locked-loop valve decoder for my Leak Troughline. Sadly, this may be of limited use on a motorcycle, due to the substantial drag incurred by the mast supporting a three-element Yagi on servo-controlled rotator.

The "Audio Anthology - When Audio Was Young" (Volumes 5, and particularly 6) have lots of useful information about fundamentals. When I looked for decent decoder chips, they had all disappeared, and only the MC1310 remains. (It's not particularly good, though.)
 
sam9

As nice as it would be in theory to do a DIY tuner so that there was a potential for a 100% diy audio system, the ultimate bummer is that quality of the broadcast signals in my area dubious to begin with. Even if it is a clear, strong signal the station compresses the devil out of it. I can't blame them from a business point of view since 80% of radio listening is supossedly done in cars where compression counters the ambient noise level.
 
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Joined 2003
The dreaded Optimod.

All broadcasters are guilty of this. It is known as the "CTF control" which stands for Compressed To something or another. I remember being proudly told by an Engineer-in-Charge that his new Optimod extended the range of his station (gaining more listeners). Optimod wouldn't be so bad if it was set with subtlety, but it rarely is, and it often follows other compressor/limiters.

Even R3 (the BBC's flagship) suffers from the Optimod, and my decoder thoughts are just for the fun of combining digits and esoteric valves.
 
A *car radio* is fairly vibration and temperature proof. Many of them have red-hot RF performance compared to ordinary radios, especially if you attach an external antenna. What's more, they come with either a cassette or CD player plus power amps. Add a small 12 volt sealed lead acid battery and speakers and away you go! I know this isn't the level of diy you where thinking about, but if this approach suits anyone else then try it and see. You won't be dissapointed.
 
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Joined 2002
I think I have found my solution. After doing a little research I think I would be out of my depth electronically building a tuner, but my local cheap stuff shop has some very small headphone style portable tuners.

I think I will buy one of these and canabalise it for my project. It should not be difficult wiring bigger buttons and moving the display off the pcb, (if I need to).

Thanks all
 
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