That's the real reason why they are going that much up in price, they fear they can't get them anymore. That applies ofc only to mint condition units. Ie the Revox B 760 goes for ~500-700€, in prestine/mint condition for 1000-2200€ though.
In America when I was growing up, AM radio (at night) was a nation-wide broadcast for clear channel stations, who were also allowed higher power and a 10KHz bandwidth, plenty for the speakers of the time. Pirate stations across the Mexican border also reached most of the country. FM existed, but it was local (within 100kM) and Fine Music, not the pop music of young boomers.
Today the world is too (electrically) noisy for AM and modern pop music is industrially produced, so FM has taken its place, especially NPR, local "community radio" and college stations. But there was a time...
All good fortune,
Chris
'Cause presently I have the related unit on my workbench, I was about to suggest the MPX decoder that German manufacturer Nordmende used in their radios and consoles with the 6/634 chassis (Tannhäuser, Arabella) from 1966 on, but although it uses a ECC81/12AT7 tube as the Grundig shown above, it is far more complicated (involving 10 Ge diodes also...).
Best regards!
Best regards!
I found the Dynaco FMx-3 module worked fairly well. It does not drift too much and provides good separation.
Circuit is pretty simple as far as a tube decoder goes.
BUT.... the inductors required are pretty hard to come up with unless you have a "donor" unit.
This seems to be a issue with all tube decoders I have come across.
There is lots of discussion on this module on the net so it is well know.
Parts only units are common for the "donor".