11-24-2022, 08:17 AM
The operating range of the RP1 and RP2 is 530 - 580 KHz. Changing C17 in the schematic below to a lower value will raise the operating range if needed.
In most areas, the lowest frequency AM station is 540 KHz. HAR (Highway Advisory Radio, otherwise known as TIS (Travel Information Service) is authorized by the FCC to operate at 530 KHz or between 1600 and 1610 KHz, but this is rather compressed in frequency response and has a range of 1 mil or less. So if you are not near a highway, and the lowest frequency AM Station in your area is no lower than about 560KHz, and you have a radio that can tune as low as 530 KHz, then you are in.
The usual repairs (changing all paper and electrolytic caps) should be done. Your biggest issue will be finding a good replacement for the crystal cartridge, which will be likely dead. There are rebuilders of these cartridges, but I don't know of any. Ceramic cartridges are available but may not have the drive needed. A magnetic cartridge will be too expensive and will require a preamp.
These "Phono Oscillators" and wireless phonographs were somewhat popular in the 1940s. RCA and Zenith also offered Phono Oscillators (I don't know if they were offered integral to the turntables; RCA radios usually had phono input terminals, and then the famed "RCA Jack"). My 41-250 does not have a phono input but has a phono button on the push button tuner. There is a sticker on the rear inside of the 41-250 that states "Built in TV Sound and FM - The Wireless Way!" (Funny, they don't mention Phono).
Don't expect HiFi out of this, especially with the original cartridge, which likely still uses a steel needle, like the original Victrola. Just the fact that the audio signal is modulating RF causes distortion (I often just patch the audio directly into the radio's amp section. I have been spoiled by HiFi and live concerts of classical and Big Band Music, but listening to Big Band Music over the radio is part of the "experience" I guess.
http://www.nostalgiaair.org/PagesByModel...013576.pdf
In most areas, the lowest frequency AM station is 540 KHz. HAR (Highway Advisory Radio, otherwise known as TIS (Travel Information Service) is authorized by the FCC to operate at 530 KHz or between 1600 and 1610 KHz, but this is rather compressed in frequency response and has a range of 1 mil or less. So if you are not near a highway, and the lowest frequency AM Station in your area is no lower than about 560KHz, and you have a radio that can tune as low as 530 KHz, then you are in.
The usual repairs (changing all paper and electrolytic caps) should be done. Your biggest issue will be finding a good replacement for the crystal cartridge, which will be likely dead. There are rebuilders of these cartridges, but I don't know of any. Ceramic cartridges are available but may not have the drive needed. A magnetic cartridge will be too expensive and will require a preamp.
These "Phono Oscillators" and wireless phonographs were somewhat popular in the 1940s. RCA and Zenith also offered Phono Oscillators (I don't know if they were offered integral to the turntables; RCA radios usually had phono input terminals, and then the famed "RCA Jack"). My 41-250 does not have a phono input but has a phono button on the push button tuner. There is a sticker on the rear inside of the 41-250 that states "Built in TV Sound and FM - The Wireless Way!" (Funny, they don't mention Phono).
Don't expect HiFi out of this, especially with the original cartridge, which likely still uses a steel needle, like the original Victrola. Just the fact that the audio signal is modulating RF causes distortion (I often just patch the audio directly into the radio's amp section. I have been spoiled by HiFi and live concerts of classical and Big Band Music, but listening to Big Band Music over the radio is part of the "experience" I guess.
http://www.nostalgiaair.org/PagesByModel...013576.pdf
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
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