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Monday, December 1, 2014

Building a Better Diode Ring Balanced Modulator (with Knack Karma)

So yesterday Pete and I were talking about Dave W2DAB's Michigan Mighty Mite malady. Dave is tantalizingly close to the joy of oscillation.  Wizard that he is, I think Pete diagnosed the problem with his eyes closed from 3000 miles away.  I sent Dr. Juliano's prescription to Dave this morning and expect the concrete canyons of Upper Manhattan to be ringing with pure 800 Hz tones as soon as Dave fires up his soldering iron. 

Anyway, I then told Pete that I'd been looking through my bookshelf for something suitable for my 11 year-old nephew Sebastian.  I found something for him, but I also came across a book that was too advanced for the young fellow:   "The Master Handbook of Ham Radio Circuits." TAB Books, 1977.  By "The Editors of 73 Magazine."   Between turkey sandwiches I started looking through this book.  I immmediately found an article of interest:  "A Better Balanced Modulator."   The author (unnamed) looks closely at the performance of our beloved and much-used diode ring mixer with dual trifilar transformers.  He concludes that the unbalanced input and output coils (in the traditional configuration) detracts from the balance needed for optimum carrier suppression.  He suggest the use of baluns at input and output (see above) and claims significant improvement in carrier suppression.   Very interesting. (If anyone wants to dig into this, e-mail me.)  There is also a very simple solid-state VFO circuit that promises phenomenal stability.   

Anyway,  I found myself trying to remember where this great book came from.  Then I remembered someone sending it to me.  A quick check of my e-mail revealed the source:  Dave W2DAB sent it to me three years ago.  Thanks again Dave!  

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1 comment:

  1. It was written by Andrew J. Borsa, WAIFRJ and originally published in March 1969. Archive dot org has a copy.

    Love my old stack of 73 and the W1SDM 73 magazine search web page http://www.w1sdm.net/cgi-bin/73search.pl


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