FM stereo decoder

[Osvaldo de Banfield]

Hi all guy's here.

Do any of you anytime did a stereo FM decoder using tubes? What can be expected from them, compared with solid state (Chip) ones? Any circuits?

I'm planing to try a complete FM AM tube receiver, designed of my own, including FI and front end coils.

Many thanks.

Osvaldo.

 

[DUG]

Found this one:

am-fm-radio-tuner-multiplex-decoder

There are probably many more out there.

 

[Osvaldo de Banfield]

Yes, thanks for your reply, I saw this last week.

 

[Sorento]

a single pentode stereo decoder:
grundig: Stereo-Decoder (1)

 

[DUG]

a single pentode stereo decoder:
grundig: Stereo-Decoder (1)

cool cct

 

[Eli Duttman]

Guys,

Both Grundig and Mr. Turner made liberal use of SS diodes. FWIW, I think Mr. Turner's decoder could be made 100% "hollow state". The pair of SS diodes in the frequency doubler would be replaced by a 6AL5. The 4 SS diodes in the ring demodulator would be replaced by a 6JU8.

BTW, any number of tube tuners used germanium diodes in their MPX sections. I suspect that lower forward drop than that observed in silicon is the reason why.

 

[Bibliophile]

Back in the seventies (I think) Fisher used a special tube which had two anodes and a pair of 'deflection plates' to do the multiplex decoding.
I've been Googling for more than an hour but can't find a reference.
Anybody recall it?

 

[Eli Duttman]

Back in the seventies (I think) Fisher used a special tube which had two anodes and a pair of 'deflection plates' to do the multiplex decoding.
I've been Googling for more than an hour but can't find a reference.
Anybody recall it?

6AR8 😉

 

[Bibliophile]

6AR8 😉

Thanks Eli 🙂

 

[stratus46]

Yes, thanks for your reply, I saw this last week.

IIRC Multiplex decoders without PLLs are a little fussy about the tuning of the 19/38 KHz frequency doubler. Separation changes pretty much.

G²

 

[benb]

Back in the seventies (I think) Fisher used a special tube which had two anodes and a pair of 'deflection plates' to do the multiplex decoding.
I've been Googling for more than an hour but can't find a reference.
Anybody recall it?

6AR8 😉

I recall this type of tube used in SSB transmitters. Here's an interesting history of "beam deflection" tubes:
Audio Synthesis via Vacuum Tubes

 

[Osvaldo de Banfield]

I know the tube with the deflection plates as 7360, often used as balanced modulator/demodulators to generate SSB signals.

Thanks for all post, the single pentode is interesting too.

happy 2013 for all you!.

 

[Osvaldo de Banfield]

OK, guy's, I found in this site a lot of circuits, I refer to you to it as any of you can experiment with them.

This is just I was searching for.

Cordially, Osvaldo.

 

[kevinkr]

Excellent news! Nice thread.. 😀

Hoping anyone motivated to experiment with a tube multiplex will post their progress here. I used to repair and modify tube decoders on a regular basis, often thought of designing and building one of my own.. I do have an old tube Heathkit multiplex I will be sorting out eventually.

 

[bohrok2610]

This is in my experience a very good discrete FM decoder:
UKW-Dekoder (only in German)
Although no tubes in the decoder and it requires dedicated coils (don't know it they are still available).

Lots of valuable FM tube stuff in the main project page:
UKW-Projekt

/Martti

 

[wiredwithtubes]

There used to be complete circuits for an all tube FM multiplex receiver in the back of the old RCA tube manuals that also listed coil specs. Winding your own coils would be quite an undertaking.
Be aware that FM HD radio uses in-band digital sidebands on each side of the main analog carrier. If you have the IF too wideband you will get interference from the digital hash.

 

[Osvaldo de Banfield]

Coils OK

Ok, guy's. Thanks for your entries. Winding coils is not a trouble for me, I have wound thousands of them from those for AM 3.5MHz to toroidal transformers, passing though the AM regenerative receiver I had pasted. Also, I have coil formers and cores, and a LRC digital meter to aproximate the inductance.

Best wishes for all the forum group in the next 2013 year!

 

[Osvaldo de Banfield]

LT Spice

Did anybody try a LT simulation for a FM multiplex signal?

 

[bohrok2610]

Did anybody try a LT simulation for a FM multiplex signal?

Here is a simulation of the aforementioned FM decoder. Not sure about the exact coil inductances.

 

[Osvaldo de Banfield]

Thank you boy!. Nice year 2013!.