[HBR] strange thing

[donald haworth]

I am in the process of building an HBR based on the Collins R392.  The IF
strip uses SIX 26a6's.  The design was 'lifted' from the '392 manual.  Once
I got it tamed, it is working very well, indeed.  My detector (AM) is a
LM-318 precision rectifier.  The input to the LM318 comes off the sec. of
the last IF transformer, via a 47k resistor.  It has amazing audio--even at
high signal levels (4v p/p).  I noticed that when I would remove the X10
scope probe from the input to the detector, I would get a rather large DROP
in audio level--just the reverse of what you would think would happen!  So I
soldered a 10 meg resistor across a 20pf trimmer cap and put that across the
input of the LM-318--where I had the scope probe....tuning the 20pf cap
brought up the audio level by a good 30%!  Tuning seems very sharp, with the
peek at 11.5pf........?
It all seems to work and as I say, the audio quality is very good..KOA in
Denver was coming in like a local last night FM -like quality---So what is
going on here?  Why is the extra load-small as it is-IMPROVING the audio
output of the detector???
--Any ideas?
Don in Nashville