[Hammarlund] Favorite Hammarlund Radio

[Byron Tatum]

Hello To All Fellow Hammarlund Appreciaters-
    My favorite is the HQ-180 as I viewed it as the "ultimate receiver" in my 
youth. There was no way I could afford one on the lawn mowing money I earned. I 
had the brochures from Hammarlund and just about drooled as I read them. I 
started out with the Heath GR-64, then had the HR-10 assembled in time for my 
novice.
    I spotted a Ham's antennas in my hometown and introduced myself. There was 
an HQ-180 on his operating table. So, I finally was able to see one in action 
and I was not disappointed! He gave me my novice test.
    I recently bought a really nice HQ-180 and went through it. A careful close 
alignment makes all the difference. It really purrs. I tried an experiment by 
separating the mixer and osc functions of the second mixer (converter 6BE6). My 
modification consisted of adding a 6BH6 osc using original crystal, and that was 
switched by the bandswitch in the same fashion as the original converter osc 
portion. This really improved the performance on the two upper bands where this 
converter was employed. Idea courtesy of W1VD.
    Another great improvement was the Dallas Lankford AVC modification, which is 
very simple and easy, it greatly improves the attack time and eliminates the 
"pop" on strong SSB/CW stations. Further AVC work was to remove AVC from the 
third mixer (converter) and add AVC to another IF stage.
    Another Hammarlund set I really like is the HQ-160. However, I do not care 
for the "linear detector" 6U8A that has both IF and BFO signals fed to grid. 
What I did to my HQ-160 was to rewire the 6U8A socket for a 12AU7A product 
detector, much like the one in the 75A-4. A separate BFO was built, well 
shielded, using original tuned circuit and a 6BH6 tube. This really worked well 
and kept the BFO out of the IF. So, the set was modified with replacement mode 
switches to allow AVC and S-Meter action with the BFO on. Suitable AVC release 
capacitors were chosen for fast/slow. This greatly improved the HQ-160 for 
SSB/CW and did not affect AM reception. The selectivity is a little lacking but 
I am studying installing a filter that would be in line on SSB/CW only. Then, I 
discovered my HQ-160 had the coupling capacitor in the link between the 
dual-frequency IF tranformers. Tuning WWV at 10 MC on the top end of the lower 
band (single conversion) was about 2 S- units better than tuning 10 MC WWV at 
the bottom end of the higher band. So, I shorted the capacitor and had the same 
signal strength on each now. Since I was fooling around in second mixer 
(converter) area I went ahead and removed the little sub-assembly box, pulled 
out the crystal and did some rewiring to change the 6BE6 from a converter to a 
straight mixer. Then, I installed a 6BH6 crystal osc much the same as I did in 
the HQ-180, however turning the osc on/off was a little different in this case 
using existing bandswitch contacts. An improvement in performance on the upper 
two bands was realized.
    On both receivers I removed the tube rectifier and built a choke input power 
supply with more filtering and slightly lower B+ voltage.
    As far as the drift I plan to do more study and see what may could be done.
    I hope I have not horrified the purists too much here, but I thought others 
may have interest in improving these fine old sets so that they will be the set 
you choose to listen to, and not be relegated to the shelf. 
                                            Thanks All,
                                                            Byron WA5THJ