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Re: Got The Urge To Work Some Aurora
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Back in my early 6 meter days, AM/CW rigs was pretty much what we had to
use. While difficult, if you did it enough times, you could use AM (you
knew what ...
2 hours ago
Very interesting article and thank you. I will politely point out that this is the American history of solid state direct conversion radios. Under the name homodyne, synchrodyne and later zero intermediate frequency this radio method was used throughout Europe for decades. It was probably invented in the UK. My grandfather from Bristol operated both tube and then much later PNP transistor homodyne receivers starting in around 1938. Since he worked for the Intelligence wireless service, his circuits and contributions to the design will never be known. Peter Colston, Cardiff
ReplyDeletePeter: Wes Hayward never claimed to have invented the direct conversion concept. If you look at his article, he states "The direct conversion concept was certainly not a new one. An excellent vacuum tube example is a design by White in QST for May, 1961." What Wes did was to take this receiver concept, and put a solid state version of it in front of American radio amateurs. Bill
ReplyDeleteyou titled this post The History of Direct Conversion receivers Bill
ReplyDeleteA year or so ago, NIck Kennedy (WA5BDU) and myself built a pair of these DC receivers and they sounded exactly as described by DeMaw and others. Was fun revisiting that bit of history.
ReplyDeleteJerry
KI4IO
Warrenton, VA
True, there were various homodyne, synchrodyne,etc efforts, but Wes's methodical approach to DCR made it practical and effective. An old vacuum tube version that I tried was noisy with heater hum. It was more difficult with my 6SN7's! The W7ZOI approach worked first time, every time.
ReplyDeleteI still use the 88mH toroid and capacitor matching network, which also effectively provides ~9-12dB less loss between product detector and Q2. This also attenuates the local guys ~100KHz away with their KW's on phone. KK7B's approach uses a common-base first stage to reduce mismatch. As always, attention to the details pay off.