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Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

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Old 23rd March 2003, 12:03 PM   #11
Cobra2 is offline Cobra2  Norway
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Default FM tuner info

You may find something useful here, even if it's most about mods...:
http://www.fmtunerinfo.com/

Arne K
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Old 24th March 2003, 08:00 PM   #12
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If I remember well, then the TDA7000 is mono. there is a stereo version, with a matching stereo decoder. You have to use that one because the IF is some strange low frequency and not the standard 10.7 MHz.
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Old 24th March 2003, 08:35 PM   #13
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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.
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Old 24th March 2003, 08:40 PM   #14
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Default 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.
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Old 24th March 2003, 11:09 PM   #15
BrianL is offline BrianL  United States
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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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Old 24th March 2003, 11:35 PM   #16
EC8010 is offline EC8010  United Kingdom
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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.)
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Old 24th March 2003, 11:50 PM   #17
sam9 is offline sam9  United States
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Default 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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Old 25th March 2003, 12:17 AM   #18
EC8010 is offline EC8010  United Kingdom
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Default 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.
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Old 25th March 2003, 01:49 AM   #19
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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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Old 28th March 2003, 07:39 PM   #20
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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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