[ARC5] Way OT -- SX-28

[Ken]

No . Q-multipliers do not work at audio: they work at the IF, period.Select-o-jects work at audio.Ken W7EKBSent via my Samsung Galaxy, an AT&T 4G LTE smartphone
-------- Original message --------From: Richard Knoppow <1oldlens1 at ix.netcom.com> Date: 8/6/21  13:12  (GMT-08:00) To: arc5 at mailman.qth.net Subject: Re: [ARC5] Way OT -- SX-28     Q-Multipliers work at audio. While they can be of considerable help they do not eliminate beat images (the beat at the other side of a CW signal) or specific QRM, i.e. a single signal, like another station adjacent to the one you want. They really do not improve the selectivity.    The original Q-Multiplier was designed by a fellow at Stanford U. I am unable to remember his name. The circuit and theory was published in QST and a commercial version was made by National under the name Select-O-Ject. Heathkit also made a version. They operated at audio frequencies so could be used on any receiver and did help with very low cost receivers with minimal selectivity.    Of course, the principle works at RF too and some receivers were built with RF selector or notch filters. These, like a crystal filter, do null out a specific signal and will eliminate CW images but the fact that a  Q-multiplier could be used without any modification to the receiver made them very popular.On 8/6/2021 12:50 PM, Hubert Miller wrote:> You folk remember that ARRL article on the Q-multiplier outboard unit for> the SX-28 ? It was published, I think, in some edition of the Handbook or> maybe in QST. Would that addition be for more variable SSB selectivity> or the notch feature, or actually both ?> -Hue Miller> ______________________________________________________________> ARC5 mailing list> Home: http://mailman.qth.net/mailman/listinfo/arc5> Help: http://mailman.qth.net/mmfaq.htm> Post: mailto:ARC5 at mailman.qth.net>> This list hosted by: http://www.qsl.net> Please help support this email list: https://www.qsl.net/donate.html-- Richard Knoppow1oldlens1 at ix.netcom.comWB6KBL______________________________________________________________ARC5 mailing listHome: http://mailman.qth.net/mailman/listinfo/arc5Help: http://mailman.qth.net/mmfaq.htmPost: mailto:ARC5 at mailman.qth.netThis list hosted by: http://www.qsl.netPlease help support this email list: https://www.qsl.net/donate.html
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