"Bill Meara" wrote in message
om...
I have an old Heath SG-6 signal generator. It uses two triodes.
I'd like to convert it to solid state. The switched coils, varible cap
and dial mechanism are very nice. Any suggestions on what kind of
oscillator circuit I should use? I imagine the difficult part will
be coming up with a feedback circuit that will cover the 160 kHz to 50
Mhz.
Any ideas? Has anyone seen any articles on this kind of conversion?
By going solid state and adding a few buffer stages I'm hoping I could
make
this thing a lot more stable. 73 Bill M0HBR CU2JL N2CQR
http://planeta.clix.pt/n2cqr

Hi Bill,

I'm in the process of doing something similar. I have (had) an old
"University" RF oscillator, 6 ranges, covers 100kHz-130MHz. Based on a dual
triode (oscillator and buffer) and a pentode for audio oscillator for
modulation. This thing looked cheap(ish) and didn't work very well, would
start and stop at various frequency settings. So I stripped it and decided
to keep the tuning cap, range switch, and tuning coils.

Rebuilt it with a JFET (J310) but had to change the circuit. Coils are
centre tapped and fed the supply voltage, so the Anode current flowed
through the coil. When the FET was placed into the circuit this overdrove
the gate and oscillation was erratic and unstable. Supplying through a
resistor improved things quite a bit.

Problem I have now is with the low frequency ranges. The coils for this are
large (they are air cored with a tuning slug?) so are high resistance as
they have lots of wire. I may try to increase gain to compensate or else
replace with a toroid.

As someone else mentioned, I haven't checked tracking so I don't know how
well the tuning dial will match the frequency.

James.