16-07-2020, 08:34 PM
Hi.
Well I've now tried the 1J18B and a 1J24B in the RF amp position. Running at 36 volts HT I find that selectivity is pretty poor even with reaction at the point of oscillation, my local is heard at low level right across the band and it floods the two adjacent stations. Drive is good though and using a 1J18B in the audio its powerful enough to drive a speaker at listenable level.
For definite the 1J42A is the best valve for the RF stage.
My plan now is to rebuild this on another board as this one has been hacked about with and is getting rough. I'll do this on a section of double sided copper laminate board for screening with a better layout. Valves will be a 1J42A & 1J18B or 1J24B. May be a couple of weeks as I'm concentrating on the Pye B16T. After the restrictions are over we will be returning to the work we do for vulnerable people in the community that has been stopped by the pandemic. So I'll have a lot less time to devote to projects.
Well I've now tried the 1J18B and a 1J24B in the RF amp position. Running at 36 volts HT I find that selectivity is pretty poor even with reaction at the point of oscillation, my local is heard at low level right across the band and it floods the two adjacent stations. Drive is good though and using a 1J18B in the audio its powerful enough to drive a speaker at listenable level.
For definite the 1J42A is the best valve for the RF stage.
My plan now is to rebuild this on another board as this one has been hacked about with and is getting rough. I'll do this on a section of double sided copper laminate board for screening with a better layout. Valves will be a 1J42A & 1J18B or 1J24B. May be a couple of weeks as I'm concentrating on the Pye B16T. After the restrictions are over we will be returning to the work we do for vulnerable people in the community that has been stopped by the pandemic. So I'll have a lot less time to devote to projects.
