[R-390] Hartley bfo FET Prod.Det.

[Dan Merz]

Hi,  I'm mostly thru the mechanical building part of the product detector
for 390a similar to the one shown by AI2Q on this list,  which has an agc
circuit in addition to the detector/bfo,  and just connects to the i.f. out,
diode load,  and agc connections on the back of the 390a.  But instead of
using the crystal-controlled bfo oscillator  I opted to use a tapped coil
bfo unit in a can salvaged from a  National NC 100.  In tapping the MPF102
FET bfo signal  into the base of the 2N2222 buffer stage,  I wonder if it's
best to take the signal from the drain,  much like an electron-coupled tube
oscillator or from the source connection.  Most circuits I find for FET
oscillators take the signal from the source,  analogous to cathode tap for a
tube, and presumably a lower impedance coupling.  Are there any opinions on
why most handbook circuits show the source connection?  I suppose either
would work by fiddling with the various coupling impedances.  I've got a
week of thinking about it before I'll be able to get back to the project.
Any thoughts?  Best regards,  Dan.