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

[Byron Tatum]

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 circuit shown 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 disconnected the 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, and disconnects lead from ground on all higher bands. I extended the 
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) I added a jumper across the paralled 18 uH RF choke and 560 pF 
cap for 6BE6 cathode.
                Just judging by ear I believe the HQ-170 benfited 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 time and 
any comments or recommendations-
                                                                                
    Byron WA5THJ