[Hallicrafters] SX-117 / HT-44 modifications - Follow-up

[Waldo Magnuson]

In an earlier posting I wrote the following:

> This note is to SX-117 owners/experts.
>
> At the recent Seattle (actually Puyallup) Hamfest I purchased a SX-117 
> / HT-44 pair.  The SX-117 seems to work fine but inside the manual was 
> a note of modifications.  The modifications listed were:
> 1.  Removed R63 to defeat delayed AGC function.
> 2.  Added full-wave voltage doubler to increase audio output power 
> (sketch was attached).
> 3.  Disconnected R78 feedback resistor to increase audio gain at the 
> expense of linearity.
> All signed by AB7YO Bruce - Feb. 2000.  Bruce if are on the forum, 
> please contact me.
>
> My question, to experienced 117 owners, should I remove the 
> modifications. The receiver seems to work just fine as is but I have 
> no comparison to make.

I was able to contactact AB7YO and he offered the following regarding 
the modifications:

Yes, that looks like the mod I made to the SX-117.  I made it to get a 
bit more umph out of the audio output tube.  It would always distort on 
loud AM or SSB voice peaks with a 4 ohm speaker.  Hallicrafters seemed 
to be in the habit of producing receivers with .75W of audio output, 
when others were routinely using 2 and 3 watt audio output.  It didn't 
totally fix the problem, but did improve it.

The switch on the rear apron was there when I got the receiver.  It 
takes the RF stage off the AGC buss.  If you are into really weak 
signal work, that might be useful to you.  It wasn't to me, but I left 
it alone anyway.

As for the delayed AGC mod, I did that because I'm just annoyed by the 
notion of delayed AGC.  It is a good concept in principle: keep the RF 
stage at full gain for weak signals and then reduce it when signals get 
strong.  But in practice, I find that it means that the S-meter doesn't 
respond to weak signals, and sometimes not even to moderately strong 
ones.  Finally, at some level, it begins to wiggle.  For myself, I 
regard the S-meter as an important indicator of signal strength at all 
signal levels.  I want it to indicate on the weakest signals, even 
though it will be reducing the receiver's sensitivity a bit.