Possible to convert 42MC-50MC FM?

[cbenham]

Originally Posted by tubesrule;
I do have a converter that is shown on the FM Only site here: [url

http://www.somerset.net/arm/fm_only_converters.html[/url]
It's down the page a little under the Crystal Devices heading. It is completely passive. I haven't gotten around to trying it either so I don't know if it works, or how well it works. Darryl

The "Converters from Magazine Articles" section of this link includes a 1 tube [6J5] and a 1N34 crystal diode converter by Harvey Keys I want to build for my Dad's Philco Console from 1940. It appears simple and the article has good instructions.
Film@Eleven

Cliff

[bgadow]

If anybody should need them, I have a few VHF tuners from about 1950-52 which are looking for a home. 2 of them are Emersons, not sure about the other one. Yours for shipping.

[vintagecollect]

Hey pentode, please post a pic of your 1025M PLEASE

thanks for tip pentode. What channel covers the other end of fm dial, channel 7?

[Penthode]

Originally Posted by vintagecollect

Hey pentode, please post a pic of your 1025M PLEASE

thanks for tip pentode. What channel covers the other end of fm dial, channel 7?

Here is my Stromberg Carlson set. It appears that Stromberg Carlson and GE were the first manufacturers to go ito FM in a big way. Stromberg Carlson launched an FM receiver in 1939, one year before FCC FM commercialization.

With the TV tuner set to channel 6 and the local oscillator adjusted upward, The radio will receive 88 MHz to 96 MHz corresponding to 50 MHz to 42 MHz on the old band. Note I reversed the old band from 50 to 42. This is because the TV tuner oscillator is set to 138 MHz. This is how it is calculated:

Channel 6 local oscillator = 87.25 MHz(ch6 snd) + 41.25 MHz (TV snd I.F.) = 128.5 MHz

Low Band FM converter osc. = 88MHz (new band low end) + 50MHz (old band high end) = 138 MHz

Further: Converter osc. = 96MHz (new band 88 + (50-42)) + 42 MHz (old band low end) = 138 MHz.

What this means is that with the local oscillator in the tuner adjusted 9.5 MHz higher to 138 MHz, the old band FM radio will receive the low end of the new band. It must be noted that the old band was 8MHz wide and the new band is 20 MHz wide, so that only a portion of the band is covered with one TV tuner channel setting. It follows that if you can rebuild the tuner to cover the entire band with three separate channel selections of the tuner, each with a progressively higher local oscillator setting. Eg 138 MHz osc. for 96 to 88 MHz, 146 MHz for 104 to 96MHz and 154 MHz for 112 to 104 MHz. Or else you can over lap. Then again you may be able to get the fine tuning control of the tuner give you extra range.

Note that I have also adjusted the TV tuner RF stages for the FM radio band. In that way you can receive more distant stations. I find with the TV tuner, the old Stromberg Carlson can receive distant stations as well as a new FM radio.

Note the inverted calibration. This is because when the local oscillator freq. is set above the incoming signal freq. the RF frquencies are inverted. Recall with analog TV, the broadcast video carrier frequency is lower than the broadcast Sound carrier frequency. The higher local oscillator inverts the arrangement in the video IF.

I hope this helps.

Cheers,

Terry

[vintagecollect]

Can eveyone who has a prewar set chime in please, especially if in use

[sean]

I have a Philco 42-1015 that I am trying to get finished up that I intend to use somewhat regularly (pre-restoration photo below). I have a place in the living room ready for it anyway. I built a converter based on the Hallicrafters CN-1 converter. I am looking for a table model 1942 Philco with FM and I thought about designing a solid state converter loosely based on the CN-1 for that.

[bgadow]

I own a pair of the prewar Philco sets (a table model and a console) but have not tackled either as of yet. I also have a Stromberg-Carlson which is waiting in line.

[DavGoodlin]

I will start a new thread but I do not understand the TWO bands these 1947 sets have. I know one is 42-50 MC, but with channel numbers instead.
The Stromberg Carlson 1210-PL is the pretty one. The other one I only have the chassis, stamped "model 1121" and cannot ID. Any ideas?
Dave 63

[Electronic M]

Perhaps those sets were meant to tune the TV FM sound carier.

[sean]

The 200 to 300 is the current 88 to 108 FM band. Those were the assigned channel numbers (which are still assigned to stations). I have a Meissner FM tuner that has both the frequency and the channel numbers for the modern band.

[Electronic M]

Why channelize radio?

[DavGoodlin]

Does that mean these had both old and new FM bands? I had the StrombergCarlson for 32 years. I had it working then and it did get a few FM stations on the 200-300 band as I recall. I left the tuner at 102.5 FM as photo shows. BTW, I had an early mobile receiver that did receive a nearby TV's leaky sound carrier on 41.25 MC.

Thanks!
Dave 63

[sean]

Originally Posted by DavGoodlin

Does that mean these had both old and new FM bands?

It appears so. The first one should tune 88-108Mc on the 201-299 band and 42-50Mc on the 21-99 band (42.1 to 49.9Mc). The Stromberg Carlson radio would tune 88-108Mc on the 200-300 band and 42-50Mc on the 20-100 band (I would assume 42.0 to 51.0Mc).

BTW, the first photo is also a Stromberg Carlson:

http://www.radioatticarchives.com/radio.htm?radio=3198

[Jeffhs]

Originally Posted by sean

It appears so. The first one should tune 88-108Mc on the 201-299 band and 42-50Mc on the 21-99 band (42.1 to 49.9Mc). The Stromberg Carlson radio would tune 88-108Mc on the 200-300 band and 42-50Mc on the 20-100 band (I would assume 42.0 to 51.0Mc).

BTW, the first photo is also a Stromberg Carlson:

http://www.radioatticarchives.com/radio.htm?radio=3198

Some older (late '40s) Zenith radios also tuned AM and both FM bands, although the old FM scale on these sets was actually calibrated in MHz (mc) rather than channel numbers on that range. The radios I'm thinking of are the old Zeniths with the arc-shaped tuning dials and the ones with round dials and a "Tone Register" tone control system. I am guessing the latter were made in the late '40s as well, owing to the presence of the old 40-MHz FM band which was eliminated from all Zenith, et al. FM radios after all FM broadcasting transitioned to 88-108 MHz by 1949 or thereabouts.

There may be next to nothing to hear on the old 42-50 Mc. band today, although I suppose one could overhear old cordless telephones which operated on the old 46-49 MHz range if such are still in existence nowadays, which I doubt -- all current cordless telephones now operate in the GHz [gigahertz] range. Most of the old 46-49MHz cordless phones have probably been scrapped, due to being forced into obsolescence by the new 5.8 GHz phones now in use.

[cbenham]

Originally Posted by Jeffhs

There may be next to nothing to hear on the old 42-50 Mc. band today, although I suppose one could overhear old cordless telephones which operated on the old 46-49 MHz range if such are still in existence nowadays, which I doubt -- all current cordless telephones now operate in the GHz [gigahertz] range. Most of the old 46-49MHz cordless phones have probably been scrapped, due to being forced into obsolescence by the new 5.8 GHz phones now in use.

You can buy "win" a 'Sentry' HO 900 FM wireless headset system on eBay for ~$20 that transmits in the 42 to 50 MHZ band, crystal controlled and sounds very good when playing a cd through it.

It works great through my Philco 42-395 console.

Cliff