Looking for "textbook" FM receiver schematic

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FenderBender11

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Joined 2011
#1
Hello,

I need a basic "textbook" example of a FM audio receiver...but I'm not sure exactly what to look for, for best results.

There seem to be a ton of ways to make a receiver, whether it is is single chip, discrete components, transistorized...etc.

Here's one that keeps on popping up whenever I search: One transistor FM radio project

Does anyone have any experience with either of those circuits, and how would they perform? I recently picked up the book "Secrets to RF Design" for $1, hoping it would have some direction...but somehow, it does not.

Any ideas?

Thanks.

(If this is in the wrong section, a moderator can move it, of course).
 
#2
#5
sofaspud said:
Have you looked at Dave Johnson's Discover Circuits? He has a lot of circuits to choose from. Joe Carr's "Secrets..." isn't a cookbook, but you got a great deal for $1.
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Oh yeah don't get me wrong. There's a lot of great information on technique and methodology. I was just hoping it would include a schematic and/or some direction. I thought it might be a good project to include.

I've looked on a lot of those circuit websites to very little avail. Either the FM circuits have been removed or they use some outdated chips etc.

I may just try Somersets 1-transistor design, and see how that works. I don't know too much about super regenerative design, so I may need to read up, so I lay it out correctly.
 
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#10
I don't remember JLH doing a tuner. The classic Wireless World tuner was by Nelson-Jones. It was available as a kit from the same firm as some JLH designs, which may be why people associate it with him instead.

The N-J tuner was sometimes partnered with the Portus and Hayward stereo decoder, but alternatively one of the standard RCA or Hitachi chips could be used.
 
#11
Yeah I'm surprised that there are so few FM kits or recent DIY articles on FM. FM is still relevant in our society.

I've been reading up on RF. Some of the more prominent ideas are to keep the circuit as tight as possible, use a ground plane (or a very low impedance ground), and to properly shield it.

I'm not sure how well it would perform because I would probably try to make it on perfboard, as I have never etched anything in my life...though I suppose I could change that.

Regarding that Somerset design...One transistor FM radio project

It calls for a 9V battery. Now I don't really know how that shunt regulator is working, but what would happen if I dropped that voltage to around 2.7-3.0V (2x AA batteries)?

Thanks for the interest.
 
#15
DF96 said:
Perf board might not work too well at VHF. OK for an AM radio, though. For VHF FM you need either a PCB or 'dead bug' style on a plain unetched PCB sheet.

If you are an RF newbie, then don't start with FM. Try a simple AM receiver first. RF (AM) is harder than audio. VHF FM is harder still.
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I made a foxhole radio when I was younger. 😛

That's about it though. I made that on a piece of wood....sounded alright. Then again, there wasn't much to hear.
 
#16
It is the VHF part which is beyond basic diy, requiring "unusual" test equipment . If you can get hold of one of the old Larsholt front end modules, that takes care of this part. The detector and stereo decoder are practical diy. My Sony STS-361 is a single sided pcb with wire links - hardly good rf practice and it works very well. One possibility is to buy an old Japanese tuner as a parts doner. Most will contain a CA3089 and MC1310 or equivalent Rohm parts and a usable tuner front end module.
 
#18
Fenderbender11; "How about FM transmitters? Do they require special layouts?" Yes, if done properly. To address the original question I recall from the schematic of one of the top end Marantz receivers that its tuner had FIVE tuned stages. If I were to consider building one that's probably the one I'd attempt to emmulate. But one of the easiest best fixes for FM sound is to build your own Stereo decoder. Don't know the modern equivalent or if it's still available but I seem to recall using a National LM1800 decoder. Made a huge difference on the receiver I was using at the time. Doc
 
#20
For me, the JLH AM/FM tuner made from a kit sold by Hart Electronics in England was a failure. I never get rid of whistles in AM and always got poor stereo separation in FM. In FM, I think the sample and hold decoder had a conception problem, but previous stages were ok.
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