[Hammarlund] HQ-170 / HQ-180 6BE6 Converter Split-Off

[Kenneth G. Gordon]

On 11 May 2011 at 20:16, Byron Tatum wrote:

> Hello-
>
> Thought I would post some results of some experimenting with a HQ-170.
> I did a couple of things:
>
> 1. Removed the AVC from the 455 KC to 60 KC converter 6BE6. I 
> connected the AVC feed resistor (470K) to ground. 
>
> 2. Added AVC to the second 60 KC IF amplifier, using 470K feed resistor,
>  bypassed with 0.02 uFD disc cap.
>
> These two AVC mods improved the strong signal listening qualities, and
> eliminated the slight pulling of converter due to AVC action. I plan to add
> AVC to the third 60 KC IF amplifier next.
>
> 3. Split up the converter (used as second mixer 3035KC to 455 KC, or as
> pass through 455 amplifier).
>
> a) Added a 6BH6 as the 2580 KC crystal osc, mounted new tube directly in
> line with T-1 / T-2. Used the circuitshown on page 566 of 16th edition
> Radio Handbook by Orr, entitled "DX Receiver". The circuit is a 6BJ6
> crystal osc. I duplicated the circuit, except used a 14-22 uH slug tuned coil
> paralleled with a 300 pF cap, in the plate circuit. Took output from plate
> through a 2 pF cap, through a miniature coax cable, over to pin #2 of
> 6BE6. Used 105 VDC regulated B+.
>
> b) To turn the 2580 KC osc on / off properly I disconnectedthe lead that
> performed this function for the original converter, connected in cathode
> circuit. The 2580 KC osc is off when operating on 160 and 80 meters, and
> on on all other bands. This lead goes to the rear of the first wafer (nearest
> front panel)of the bandswitch.  It grounds the lead on 160 and 80 meters,
> anddisconnects lead from ground on all higher bands.  Iextendedthe lead
> and connected it to the cathode of the 6BH6.  In the circuit the cathode of
> 6BH6 is grounded through a paralleled 1 mH.RF choke and 75 pF cap.
> The 6BH6 will not oscillate when the cathode is directly grounded.
>
> c) Iadded a jumper across the paralleled 18 uH RF choke and 560 pF cap
> for 6BE6 cathode.
>
> Just judging by ear I believe the HQ-170 benefited from having a separate
> osc and mixer in this part of the circuit, as the spurious responses I could
> tune on the 10 meter band are not appearing anymore, plus the receiver
> seems a little quieter and more sensitive on higher bands.
>
> Am considering this for my HQ-180 but have not studied the chassis layout
> for where to add the extra tube. 
>
> Thanks for the time and anycomments or recommendations-      
> 
> Byron WA5THJ

Ya done good, Kid. :-)

Personally, I have always disliked pentagrid converter tubes. The 6BE6 is 
NOT one of my favorite tubes.

Thanks for the info, and if you do anything similar to your HQ-180, I would be 
very interested in your results.

Ken Gordon W7EKB