[Hammarlund] RE: SP-600 BFO

[Christopher L. Cowan]

I have made the modifications included in the article:

http://www.hammarlund.info/info/sp-600/detector/

Which includes, among other things, rewiring the SP-600 audio system for a product detector.  The article describes mixing the low BFO output with a lower level IF in a produdt detector.  This involves rewiring the audio system entirely but the performance is good.

I had two troubles.  One was severe microphonics from the 6C4 prod det which was solved by replacing with a ruggedized version or equivalent and  second, hi freq audio oscillation at mid and higher level audio control settings.  The latter was solved with additional HF roll off in the audio filter network.  I could not find the cause for the feedback but the filt worked.

Check out the article which is in five .JPG files.

Regards

Chris Cowan, KA0A/7

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