[Hammarlund] HQ-180 versus HQ-180A

[Roger D Johnson]

Leigh Sedgwick wrote:
> Mike, K7PI wrote:
> 
>>What are the main differences between a HQ-180 and HQ-180A?
> 
> 
> Thanks to all for the response to my question.  Here is
> a summary of the responses:
> 
> 1.  My favorite - one has an "A" after the number and 
>     the other one doesn't!
> 
> 2.  The tuning gear design is greatly improved in the
>     "A" by mounting the gears inside the frame instead 
>     of outside, reducing wobble.
> 
> 3.  A cabinet that opens on top (note:  my HQ-180 
>     non A has also has a cabinet that opens on top.  
>     Wish my HQ-170 also had this feature).
> 
> 4.  Two critical tubes, the 6C4 and the mixer tube 
>     stay on when the radio stay on when radio is 
>     shut off to improve stability.  A special jack for 
>     the clock so the AC doesn't turn off these tubes. 
>     Makes disassembly easier if needed.
> 
> 5.  Solid state rectifiers.
> 
> 6.  Switchable between 120V and 240 V. 
> 
> 7.  The "A" tends to be more expensive.
> 
> Thanks again for the information and Happy New Year to all!
> 
> 73 de Mike
> K7PI
> www.k7pi.com (http://home.comcast.net/~bipi/home.html)
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> 
There is another difference. The A models have a 9pf capacitor
between the primary and secondary of the 455 kHz IF transformers.
This broadens the "nose" of the selectivity curve but it also
increases the gain to excessive levels. I tamed mine by putting
a cap (270 pf, I think) from the grid of V-5 pin 7 to ground.
This forms a capacitive voltage divider and reduces the gain to
about the same level as my HQ-170 (non-A).

73, Roger

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