EMRFD Message Archive 6315
Message Date From Subject 6315 2011-05-17 07:30:51 KK7B Static Hi Dave--your last sentence: "Static crashes are crisper and less reception-disruptive
when received with only heterodyne detection." needs further discussion. I think that statement holds one of several keys to what makes the difference between a remarkable HF receiver and an uninspiring one.
The modern resurgence of amateur direct conversion seems to have been kicked off by the arrival of Wes Hayward and Dick Bingham's little receiver at ARRL headquarters in the late 1960's, and the post-modern era in 1980 when Roy Lewallen's little transceiver arrived at the same place. In each case, listeners at Newington noted that these simple receivers weren't merely adequate, they were remarkable.
When a static crash hits a front-end mixer, 2nd order distortion generates DC offsets, and a large impulse appears at the IF port. A wideband resistive termination provided by a diplexer or perhaps intentional resistive loss at that point gives the impulse energy somewhere to go. That may be even more important than previously thought.
For the next chapter in receiver understanding, we might want to roll back the calendar a century and pick up where Armstrong left off--studying the 2nd order response of the first few stages of a receiver to short high-voltage impulses.
6322 2011-05-17 22:13:52 davidpnewkirk Re: Static