On Sat, 16 Aug 2008, Chuck Forsberg WA7KGX N2469R wrote:

On Sat, 06 Sep 2003 13:29:08 +0000, John wrote:

1. Does the fact that this set has double conversion make it more
sensitive or selective ? It seems to be no better than my S-40B ? 2.The
volume and sensitivity controls must be at almost set to maximum to
receive anything on 80 meters or higher. Is this normal ? Any
suggestions on what to check ?
3.Will this set be more sensitive on a di-pole antenna ? I only have a
vertical connected to the co-ax connection . 4.The selectivity controls
has two capacitors about 1.25" long and3/8" thick with red, red, orange,
white, blue bands. What is value ?

I have replaced all caps, bad resisters and none of the tubes have
shorts. The alignments seems fairly decent on all bands, but I have not
attempted to adjust. (Don't trust myself to do this...).

Any and all help is appreciated.

Thanks,
John

The double conversion reduces image response compared to
the the S-40. This becomes a problem above 10-20 MHz
depending on the Q of the RF coils and how well the radio
is aligned.

The 5 selectivity choices on the S-76 would help receive
weak signals.

The S-40 is a much simpler radio and easier to align.
The S-7 alignment procedure calls for a 50 KHz signal
which is not provided by most signal generators.

If it's a 50KHz final IF, then that would tend to give better
selectivity. After all, at that frequency you can get plenty of
narrow bandwidth without anything more than a few IF transformers.

It's not just the selectivity, but you get better shape factor
with just the IF transformers at 50KHz as opposed to 455KHz.

And they wouldn't go to the trouble of dropping to 50KHz unless
they were seeking better selectivity than 455KHz would offer.

And given a 50KHz IF, they didn't have much choice but to go
to double conversion, since a 50KHz IF would mean either lousy
image rejection or a lot of tuned circuits at the signal frequency.

Michael VE2BVW