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Friday, February 19, 2016

Inside the Hammarlund HQ-100

I continue to work on this old beast.  I picked it up in the Dominican Republic around 1994.  One of the IF transformers had gone open.  I fixed that.  Had to replace the AF output transformer too. And the variable cap that tunes the antenna.  Check out the flywheels!  And the rope and pulley thing.  You don't find those kinds of things in any of those fancy modern rigs. 

Earlier I had removed "the exclusive Auto-Response audio output circuit."  See:

Today I installed a simple feedback network in the AF amplifiers (as prescribed here:  

It sounds nice now.   The rest of the bands have been ravaged by some sort of solar event, but 160 seems to be benefiting -- signals last night and this morning were quite strong.  I was being heard by WA1HLR way up in Maine.

UPDATE 20 Feb 2016: After installing the feedback network mentioned above, I noticed a big increase in AC hum.   It was not the electrolytics.  I reversed the feedback mod and the hum went away.  But the receiver continues to sound a lot better with the removal of the Auto-Response output circuit.

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