[Elecraft] P3 and HQ-170A

[Alan Bloom]

I downloaded the HQ-170A schematic and took a look at the schematic.  It
looks like the 455 kc output is taken directly from the plate of the
second mixer through a 10 pF (oops, I mean 10 mmF :=) capacitor.

Since 10 pF has 35 kohms reactance at 455 kHz, you'll probably need a
buffer to drive the P3's 50-ohm input.  You could use a cathode follower
(if you want to be authentic) or an FET source follower (with clamp
diodes at the input to protect the gate from voltage transients).

Let us know how it turns out.

Alan N1AL
  

On Thu, 2012-02-09 at 21:03 -0800, Phil Hystad wrote:
> So, I get my Hammarlund HQ-170A out of the storage garage because I
> got a re-tubing kit and I am finally going to replace some or all of
> the tubes.  The HQ-170A works but audio is a little on the weak side
> and sensitivity could be improved.  I will do the tube thing first and
> then maybe consider some alignment experiments.
> 
> But...
> 
> I noticed on the back, something I have never noticed before that I
> remember, is that there is a 455 KC (well, it says KC) IF output.  I
> am guessing I might be able to plug this into the P3.
> 
> Am I guessing right or is there some other stuff I might have to
> consider -- such as signal level (voltage) or other things.
> I don't suppose anyone out there in Elecraft-land has hooked their
> HQ-170A receiver up to the P3.  If so, let me know how it works.
> 
> 73, phil, K7PEH
>