[Hammarlund] HQ-180/HQ-170A audio comparison video

[Robert Sauvan]

Yes,
After looking at the video myself I did notice the fact that my 
receivers were at a different pitch and was a concern of mine as well 
since that same thought came to mind. I knew right away it would be 
addressed. It was getting late so I threw it up on the site quickly 
anyway. I believe it did raise questions and comments as to what may be 
going on though which was my main target for making the video. The agc 
circuitry was a topic in previous emails so it looks as though I should 
concentrate on that area of the radio to see whats going on there. I 
will do a new video and get both receivers on the same pitch since I 
will be taking some time off for the holidays. This will be a better 
"before and after" when I find my issue. I believe the video has 
achieved its goal at this point and gives me a more direct approach to 
my troubleshooting effort. The radio is not a pleasure at all to use or 
listen too. It may be a while before you hear back, I have lots of input 
and articles to read before attacking this thing. I will go through each 
suggestion one a step at a time. As always I will post questions if 
needed as I get through it.

Thanks for all of your help

Bob-W0YBS


On 12/17/2014 10:33 PM, Kenneth G. Gordon wrote:
> On 17 Dec 2014 at 22:07, Robert Sauvan wrote:
>
>> Hi all,
>> Everybody has been a great help in trying to troubleshoot my HQ-180
>> audio issue.
>> In an attempt to find a cure for what I feel is a distortion problem on
>> my HQ-180, I decided to make a short video comparing my 180 with my 170A
>> since it is difficult to actually explain what I am hearing.The video
>> isnt quite as good as hearing the comparison in the shack, but Im hoping
>> for everyones opinion. Let me know what you think. Click the link below
>> to take you to a temporary page on my website.
>>
>> Thanks-Bob-W0YBS
>>
>> http://w0ybs.com/w0ybs_025.htm
> First of all, it sounds as though you are not using the same loudspeaker
> for both receivers.
>
> Secondly, if you want us to compare what you are hearing on the two
> receivers, you should try to set them both at the identical audio pitch.
> You have the 180 tuned to a much lower pitch than the 170. That makes it
> somewhat difficult to accurately compare the two receivers.
>
> Thirdly, to me it is VERY obvious that the AGC is always on with the 180,
> but is turned off on the 170....OR, the AGC is working correctly in the
> 170, but is not working correctly on the 180.
>
> Lastly, what you are hearing on the 180 are what is called "popping on
> peaks" if it was listening to an SSB signal: this is due to the AGC
> allowing a very strong pulse from the signal to hit the receiver before
> the AGC can "grab" it and drop the receiver's gain. It sounds as though
> you have the AGC set to "Fast", but there is a slight delay before it
> activates. The attack-time of the AGC is a bit too slow.
>
> What you are, essentially, hearing are receiver-generated key-clicks on
> the 180.
>
> I suspect the problem is in the AGC circuitry.
>
> THis would also explain why the RF gain control is not working the same
> way as it is on the 170: the 180's AGC is controlling the gain and,
> essentially, bypassing the RF gain control.
>
> I think you need to take a very close look at the 180's AGC circuitry.
>
> And, by the way, AGC circuits can be very difficult to troubleshoot. The
> 180's is especially difficult because Hammarlund's schematic for that
> receiver is extremely "messy".
>
> Ken W7EKB
>