28-09-2017, 09:21 PM
Hi Michael.
Many thanks for the reply.
I did have a thought over an hour ago and I decided to open up the shed and do some measurements.
I'm using the 1j42a on its own with the circuit I posted a last week. The supplies are an AA Ni-Mh via a resistor to give about 1v for the filament and a PP3 alkaline that has been used for 6 months with a nominal voltage of 9.1v.
I connected the scope to the 1j42a anode via an X10 probe. with no AF drive I have slightly over 8v p-p sine wave at 1566Khz, perfect waveform with no clipping, then modulate with 1Khz AF on the opposite grid and increase level, I get to nearly 80% modulation then distortion occurs, I still have the maximum of 8v p-p, the trapezoid looks spot on until 80% then it crushes.
I can do a YT clip tomorrow if you doubt my findings.
So the question is how much can "doing it correctly" improve the circuit and performance?
The whole idea of this was to make a simple pantry transmitter that gave sufficient volume and range to drive a few old radios. I have succeeded in my aim, it follows conventional valve theory, works well and has been replicated on at least two other occasions.
Many thanks for the reply.
I did have a thought over an hour ago and I decided to open up the shed and do some measurements.
I'm using the 1j42a on its own with the circuit I posted a last week. The supplies are an AA Ni-Mh via a resistor to give about 1v for the filament and a PP3 alkaline that has been used for 6 months with a nominal voltage of 9.1v.
I connected the scope to the 1j42a anode via an X10 probe. with no AF drive I have slightly over 8v p-p sine wave at 1566Khz, perfect waveform with no clipping, then modulate with 1Khz AF on the opposite grid and increase level, I get to nearly 80% modulation then distortion occurs, I still have the maximum of 8v p-p, the trapezoid looks spot on until 80% then it crushes.
I can do a YT clip tomorrow if you doubt my findings.
So the question is how much can "doing it correctly" improve the circuit and performance?
The whole idea of this was to make a simple pantry transmitter that gave sufficient volume and range to drive a few old radios. I have succeeded in my aim, it follows conventional valve theory, works well and has been replicated on at least two other occasions.
