11-08-2014, 08:33 PM
I almost have this thing working.
There is little to no gain through the mixer stage. It occurred to me that the reason why the gain was so low is from the antenna tank being out of tune.
So I stopped the osc and coupled a 1000khz signal in the antenna and tuned the radio for peak through mixer stage. Next I let the osc run and measured it and it didn't agree. ( I just bought a frequency counter)
The peak of the antenna circuit is off (low) by 150khz and won't tune up. This is in comparison with the osc frequency minus the I.F. I can't get either one to tune so they agree.
Of course the antenna loop coil has been mangled and is the inductor in this tank circuit.
Does anybody know what the inductance of this coil should be? Or even how many turns there should be?
UPDATE
Sometimes I am my own worst enemy. After glueing the antenna coil back together I hooked it up with about 18 inches of speaker wire to extend it to the chassis. Well that totally messed it up. Once I put the antenna coil back into the case and hooked it directly to the chassis it tuned nicely. For what it's worth it measured 190uh with the chassis in the case.
Next I will see what I can do for an FM antenna.
There is little to no gain through the mixer stage. It occurred to me that the reason why the gain was so low is from the antenna tank being out of tune.
So I stopped the osc and coupled a 1000khz signal in the antenna and tuned the radio for peak through mixer stage. Next I let the osc run and measured it and it didn't agree. ( I just bought a frequency counter)
The peak of the antenna circuit is off (low) by 150khz and won't tune up. This is in comparison with the osc frequency minus the I.F. I can't get either one to tune so they agree.
Of course the antenna loop coil has been mangled and is the inductor in this tank circuit.
Does anybody know what the inductance of this coil should be? Or even how many turns there should be?
UPDATE
Sometimes I am my own worst enemy. After glueing the antenna coil back together I hooked it up with about 18 inches of speaker wire to extend it to the chassis. Well that totally messed it up. Once I put the antenna coil back into the case and hooked it directly to the chassis it tuned nicely. For what it's worth it measured 190uh with the chassis in the case.
Next I will see what I can do for an FM antenna.
!!!!!!!!!!!!!!!!!!!RESISTANCE IS FUTILE!!!!!!!!!!!!!!!!!!!!!!
/\/\/\/\/\/\/\/\/\
[Image: http://philcoradio.com/phorum/images/smi...on_eek.gif] Chris