I've been having lots of fun returning one of this receivers to its old glory. For the most part is going pretty well, mostly realignment , specially the IF cans. The problem I'm having is with SSB and only above 10 Mhz, as the sound "warbles" , not clear like in the lower bands. Even the xtal marker sound exhibits this distorsion, but only in the 2 higher bands. Has anybody experience this on this HQ radios? thanks for any pointers in advance.

The 6C4 HF oscillator is the most common cause of such problems in the HQ series receivers and just because it tests OK in a tube tester does not mean it will work well in the receiver. In general, owners of the HQ series receivers that use a 6C4 HFO should have a few on hand to select the one which works best.

HOWEVER, given the problem only shows up on the two highest ranges it may well be a problem with V4, the 6BE6 converter/amplifier stage. Only on the two highest ranges (starting with 10 Mhz) does the receiver operate as double conversion so I would first try substituting another 6BE6 tube here. A small amount of heater/cathode leakage would be enough to hum modulate the signal. You could also try listening to the note from the crystal oscillator in this stage on an external receiver (with its BFO on and tuned to 3.49 Mhz.) to see if the crystal oscillator has a clean note. The HQ-160 must be on the fifth or sixth range because otherwise V4 simply provides another stage of 455 Khz. amplification.

Rodger WQ9E

Hi for Hmmarlund's I recommend using the military 6C4W tube. As he wrote the 6C4's can test fine but can cause a host of problems. Never had to wonder with the mil 6C4.

Good luck

Bill KB9IV

Yes, replacing V4 did the trick! Now it sounds just like the lower bands !! Thanks a lot... boy this is a very nice BA.. if I could just modify it to get AVC working on SSB that would be great. Playing with the rf gain all the time gets old after a while.

Glad your HQ-160 is now working as it should.

The combination of using a product detector but not setting it up for AGC on CW/SSB was an odd design choice. The National NC-270 has the same setup and although a comparison between the two is apples and oranges I much prefer the HQ-160 over my NC-270.

The Hammarlund HC-10 SSB adapter works very well with the HQ-160 and using a HC-10 with the HQ-160 provides perhaps the most versatile setup of the HQ series. For AM you still have the broader bandwidth available when conditions are good and the HC-10 provides narrower bandwidths and selectable sideband on AM when conditions are rough. For SSB you get AGC with selectable release times. The HC-10 provides you with the equivalent of the final mixer, 60 Khz. IF, detector, and audio system of the HQ-170 and also has a slot filter and noise limiter. It is self contained except for speaker and all it needs is the 455 Khz. IF feed from the receiver to work. Mine is now set up with my HQ-160, prior to that it spent several years attached to a TMC GPR-90. My GPR-90 now has the matching TMC SSB adapter which has an extremely sharp filter in its 17 Khz. IF section but I often miss the versatility of the HC-10 now when using the GPR-90.

I pointed out in an earlier posting that it should be possible to get the AVC working, the S-meter working, and insert a longer time contant for AVC action on SSB.

It takes a 3PDT switch, some wire and a cap (in red below). The cap is only if you need to slow the AGC action and would be selected subjectively.Curtis Eickerman

No doubt the HC-10 SSB adapter sounds like the best option, but probably will cost me more than the radio itself. Meanwhile I've tried lifting the AVC line and enabled the S-meter like Curtis suggested and is a lot better, I could set the rf gain at max all the time and without distortion, and the s-meter works too !!. Also tried different caps on the AVC line without much success. How to get fast attack and slow decay at that point is my next goal. Any ideas Curtis? thanks.

You could try this way. If you can't get a long enough decay, the third pole then can come in handy for another slight change. I show it being used here with a 1M resistor, but that can be changed to alter the decay time.

You will still have to fiddle with cap value. You might try something like 0.1 uF for starters. It should have a relatively short charge with a longer decay. You should be able to go up on the value until the charge gets too slow and causes popping on the first syllable. If that isn't long enough for the decay rate then start increasing the 1M.Curtis Eickerman