[Hammarlund] HQ-160 Work

[Byron Tatum]

Hello-
    Just a report to fellow Hammarlund enthusiasts about some work I did to an 
HQ-160. I hope I do not offend any purists as holes were drilled and punched. I 
believe the receiver is quite a bit more usable, however.
    1. I reworked the 6BE6 converter by removeing the little subchassis 
containing the 6BE6 and T-2. Took out a couple of capacitors and the 3490 KC 
crystal. Rewired it as a straight mixer, the same as the first mixer, with a 
sub-mini teflon coax bringing in LO signal. Replaced the module in receiver. 
Removed the coax cable that went from 6BE6 screens to bandswitch (this 
originally turned on / off the 3490 KC osc section of 6BE6).
    2. Installed a 6BH6 3490 KC crystal osc over near canned electrolytic cap. 
Used a 150K screen dropping resistor. Turning the osc on/off by grounding the 
screen pin of 6BH6 using bandswitch contacts that were freed up previously. Put 
a 270 ohm resistor in series with this grounding lead. The 3490 osc 
is activatedon on the upper two bands. The performance on upper two bands in 
improved some by this conversion to a mixer, with separate osc.
    3. Installed a 6BH6 tube toward very front of chassis, adjacent to BFO coil, 
inline with 6AQ5 and 12AX7. Placed a small, square tinplate box around tube 
socket on chassis underside, to shield the tube socket wiring from 12AX7 Q-Mult 
tube wiring. Used feedthru caps and submini teflon coax, wired this up as the 
new BFO osc. using original BFO tued circuit.
    4. Stripped the parts from 6U8 "BFO / linear detector" tube socket. Re-wired 
this as a 12AU7A twin-triode product detector, very similiar to version in 
Collins 75A4 receiver. Fed IF signal to one triode grid, the BFO to the other 
triode grid.
    5. I am in process of replacing the "AVC / MAN / CW" switch with one where I 
can operate AVC with the BFO on. I have already operated the receiver in this 
fashion by disconecting the two AVC lines that are grounded by switch when the 
BFO is turned on. The new product detector really sounds good with AVC. I 
experimented with some mylar caps increasing the release time on the IF AVC 
line. Also, I jumpered the S-Meter connections that are opened up when BFO is 
turned on allowing S-Meter action using product detector. I was very glad there 
is no detectable BFO leakage into the IF.
    6. Removed the tube rectifier and socket, converted power supply to solid 
state and installed a nice hermetically sealed choke over tube socket hole, 
making supply choke input.
    7. Replaced some of the "couplet" modules with discrete components.
            OK, I guess enough description of my butchery here. But, I have 
heard people inquire about having AVC with product detector use, and with the 
original detector that would probably not worked well as both IF and BFO were 
fed to same grid on the pentode section of 6U8. Since I had broken up the 6BE6 
converter (second mixer) on a HQ-170 and HQ-180, and liked the results, I wanted 
to try it on this HQ-160.
                                                                    Thanks, 
Byron WA5THJ