[Ronin61]

I know some of you have early 40's sets with Fm bands, what have you done as far as restoring the fm . Did you recap the chassis and what were your expectations. Did you receive any stations or am I just wasting my time. Here is a picture of the chassis before any restore.[Image: http://i1281.photobucket.com/albums/a508...156849.jpg]

[skyscraper]

According to radiomuseum.com, this uses the old 42-50mhz FM band. Nothing to listen to there without a special transmitter.

[morzh]

You do not necessarily need a transmitter, you could use a converter.

http://www.somerset.net/arm/reprints/one...ter_p1.gif
http://www.somerset.net/arm/radio_age_july99.html

Or this guy uses a modified TV tuner to convert FM band. His Z sounds pretty nice even over youtube.


The Zenith I just bought has the same 1941 FM band. Will have to deal with that when the restoration is done.

[Arran]

I think that you may be able to receive some ham stuff on at least part of the old FM band, but for the most part there isn't anything on it. On the other hand if you can come up with a part 15 transmitter that operates on that band it's pretty much an open channel.
Regards
Arran

[TA Forbes]

The FM circuitry on any set can be finicky to work on. You want to pay attention to lead dress and length and do NOT get creative with placement of components.

The FM band on my Stromberg Carlson 1025 is 21-99 MHz. I discovered that by mindlessly, and I mean that literally, screwing with the FM alignment AND experimenting with antennas that I can pick up several "modern" FM band stations. I believe that I am picking up harmonics, but they come in in an acceptable manner.

[morzh]

Yeah this is what sets apart RF engineers from mere mortals. What looks like a wire for one is a quarterwave transformer for the other.

[rocketeer]

I just left the FM chassis unplugged on my 535M. It saves 1/2 an amp in current draw.

Larry

[Penthode]

Actually the 925M scale is marked 21 to 99 but tunes 42.1MHz to 49.9MHz. The FCC assigned channels for the broadcasters for the old band and the new band. The old band FM channels were 21 to 99 and the new FM band channels are 200 to 299. The channel numbers fell into disuse in the late '40's.

As for a signal, I have made a hobby of converting old TV VHF tuners to FM old band to new band translators. A TV tuner IF output is in the 40MHz range, perfect for the prewar FM radios. Because the old band is 8MHz wide and the new band is 20MHz wide, the VHF tuner may be converted to provide three overlapping 8MHz bands eg 88 to 96MHz, 94 to 102MHz and 100 to 108MHz. I sweep align the 8MHz bands for each ensuring a good flat response with good gain. The good signal to noise afforded by the newer TV tuner works extremely well with the old prewar FM set: I find a properly restored prewar FM set generally with as much sensitivity as a new FM set and of course the sound is fantastic. It is a testimony to E H Armstrong how good FM must have sounded in 1941!

It is surprising how many prewar FM sets survive. (I have a Stromberg Carlson and two Capeharts and am looking for a Philco).

[TA Forbes]

A great tutorial on early FM !!

The 925 and 1025 are the same, but my 1025 is a LARGE table set.

Where in C. NY are you? I used to live there many moons and a couple of wars ago.

[Penthode]

I live at the border between the countries of Stromberg Carlson (Rochester) and GE (Syracuse)!

[TA Forbes]

I lived between the land of GE unemployed (Syracuse) and GE unemployed (Utica). I still go up there every summer to camp in the Adirondacks.