[ARC5] Way OT -- SX-28

[radio_man at wbsnet.org]

I have a National SAF-1-2 Select-O-Ject, it was hooked to an SX-28 which I
sold a while back. Yes it connected to the audio chain. The National also
has a terminal to connect a key so you can use it as a code practice
oscillator I also have a Heathkit QF-1 Q-multiplier, it does not hook to
the audio circuit, rather connects to the 455Kcs (Khz) IF at the mixer.

Rod
K0EQH


>     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 Knoppow
> 1oldlens1 at ix.netcom.com
> WB6KBL
>
> ______________________________________________________________
> 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