[Hammarlund] HQ-180A Audio Sound

[Robert Sauvan]

Thanks for your input Byron. I have printed out your suggestions as well 
as others and will attack each one systematically. I have accumulated 
quite a book of info to sift through so I think it is going to take some 
time to get through it all. But, at this point, I believe I have a 
better direction to approach my problem.

Will let you know what turns up..

Bob-W0YBS


On 12/18/2014 12:00 AM, Byron Tatum wrote:
> Hello Bob, W0YBS-
>     I listened to your comparison video of the HQ-170A and HQ-180 receiving the CW of W1AW/3. I am wondering if the AVC is causing the effect, or if it is a combination of AVC and audio distortion.
>      #1. I had to take the AVC feed off of the 455 KC to 60 KC converter tube (6BE6) in one of my HQ-180's to stop a slight freq shift as the AVC voltage followed signals. I just took the AVC feed resistor (470K if I recall correctly) and disconnected it from the AVC bus, then connected the disconnected feed resistor lead to ground. The issue was a very slight "warble" effect.
>      #2. The AVC attack time needs to be sped up in stock HQ-180's. All this involves is to bridge across a 1.0 meg resistor in AVC line; I do not have my manual or notebook here handy. All of the desirable AVC mods for the HQ-180 were written up in a nice article by Dallas Lankford. Mostly the mods revolved around bridging this resistor and adjusting the 3 release times to be more suitable. I was very pleased with these AVC mods, plus they are easy to do and very simple.
>       #3. I added AVC feed to additional stages in several of my HQ-170/180 radios. I do not have my notes here handy but as best I recall there is no AVC feed to the 455 KHz IF amp and no feed to one (or maybe two) 60 KC IF amps. I do remember adding AVC feed to the 455 KC IF amp and to one of the 6BA6 60 KC stages. This really tamed the receiver down and made strong SSB signals easier to listen to. I used 470K resistors, bypassed with 0.1 uFD caps on AVC bus side of resistor.
>      #4. There is an email exchange between some good folks that detailed audio mods to address audio freq response and distortion. I believe the emails are at AM Fone.Net. Check with Larry W9MDX, Kim W8ZV or Les Locklear.I have done these mods in several HQ-170/180 radios.
>       #5. Check component values and voltages around area of product detector to make sure all is well there.
>       #6. If you have done any significant work in power supply that affected voltages insure that the VR tube dropping resistor does not need to have its value adjusted. I lowered the B+ in some units and needed to reduce value of dropping resistor to VR tube.
>       #7. Proper IF alignment at 455 KC, and esp 60 KC is very important in these radios. This is discussed in the same email chain by W9MDX and W8ZV.
>                            Hope this may help-
>                                       Byron WA5THJ
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