I have an old battery TRF radio from the 1920s, I run the A supply off an old computer power supply, and have a B eliminator running from a variac. At the high end say 1200 KC and above, there's lots of volume running B supply at 50 to 60 volts. At the low end, I must up the b supply to about 90 to 100 VDC. I have about 10 feet of aerial. Any suggestions why low end needs all the more B supply?

Hi Bill

I've also seen this on early TRF radios. Believe a lot has to do with layout. There is capacity between circuits everywhere. The higher you go in frequency less capacity needed for regeneration/oscillation. You might find this capacity actually makes a radio go into oscillation at the high end with 90 volts.

Norm

:I have an old battery TRF radio from the 1920s, I run the A supply off an old computer power supply, and have a B eliminator running from a variac. At the high end say 1200 KC and above, there's lots of volume running B supply at 50 to 60 volts. At the low end, I must up the b supply to about 90 to 100 VDC. I have about 10 feet of aerial. Any suggestions why low end needs all the more B supply?