COLIN LAMB wrote:
snip
IF bandwidth is wide enough for good am, but some audio engineer came up
with the bizarre idea to vary the fidelity of the audio output depending
upon the avc voltage. It was called "Auto-Response" and assured distortion
when there was qsb. The fact that they promoted it rather than hiding it
never did make sense.

Hi,

The audio feedback percentage is not dependent on the AVC voltage,
but on the setting of the audio gain pot. If you leave the audio
gain at a low setting, you get more negative feedback,
hence a smoother audio response. The feedback is via resistor
R80 (100 Ohms) at the audio output transformer secondary,
to R77 (47 Ohms) between the bottom of the 1 Meg audio gain pot
and ground.

My HQ-170 audio sounded a lot better with the cardboard back removed
from the matching Hammarlund speaker housing.

My HQ-170 responded very well to an alignment, although it is more
drifty than I like. I picked up a small filament transformer
for the VFO and mixer tube continuous filament voltage mod,
but haven't quite gotten around to installing it yet.
(Can it be 5 years, now?)

73,
Ed Knobloch