On Dec 25, 8:52*am, "COLIN LAMB" wrote:
Hi David:

It is hard to tell from the facts you gave us. *It might be useful to feed a
signal generator into the scope and compare to factory specifications. *The
1 pf coupling capacitor could be less capacitance, and simply let less
signal through. *Or, your RG-62 could be lossier that expected.

I assume the input to the SB-610 is properly tuned to the correct frequency,
since there were different "front ends" available for the SB-610. *If the
front end is not tuned properly, then the indications of the SB-610 will be
misleading, even though you have increased the gain.

73, *Colin *K7FM

Colin,

Thanks for the reply.

I had to wind my own coils for the grid and plate tank circuits of the
SB-610’s vertical amplifier that’s based on a 6EW6 tube. The tank
circuits are peaked at 3.395 Mhz, the IF frequency of the SB-301. I
used no. 30 magnet wire and ferrite slugs from what were probably 455
Khz IF cans littering my junk box. I suppose these coils could have
less Q than what the original Heathkit coils had, but I doubt it.

So, yes, the “front end” is properly tuned and the RG-62 patch cables
are constructed from stock coax I’ve used in other applications
without trouble.

Maybe the SB-301 IF strip has less gain than usual, but the receiver
doesn’t seem to be insensitive. One remedy might be to use a coupling
capacitor larger than 1pF, as you suggest, but I calculate that this
will make little difference, as the SB-610’s input impedance is 100K
Ohms.

Perhaps I should ask a different question: For an S9 signal and the
vertical gain control set to 12 o’clock, what’s the height of the
trace on your SB-610?

-Dave Drumheller, K3WQ