Jerry,
Sorry - you are quite wrong on this :)
If you have a carrier at 9.000 and a tone at 9.0015, subtract 5.000 for
80m and you get carrier at 4.000 and a tone at 4.0015.
*USB* both at the IF and at the RF output frequency
If you write down the simple expression:
RF = IF - LO for 80m
RF = IF + LO for 20m
the absence of any minus sign before the RF or IF terms proves there can
be no frequency inversion between them.
If you've ever built a radio using that mixing arrangement you will know
that you need two 9MHz BFO crystals: a USB one for 20m and a LSB one for
80m.
This one of the longest running Ham Myths I know :)
73,
Steve G3TXQ
On 16/04/2011 20:14, Dr. Gerald N. Johnson wrote:
> No Steve you are wrong. There is side band inversion. I was there.
>
> Look at it this way. say you have a carrier at 9.000 and a tone at
> 9.0015. Subtract 5.000 for 80 meters, the carrier comes out at 4.000 and
> the tone comes out at 3.9985, LSB. Add 5.000 for 20 meters, the carrier
> comes out at 14.000 and the tone at 14.0015, USB.
>
> Its NOT folklore or myth, its the truth. AND IT IS THE REASON FOR THE
> SIDBAND CONVENTION we have today and that is fundamental to the Corsair
> and Corsair II normal sidebands because they use they same mixing
> schemes as did many Tentecs before them. In the OMNI VI they arranged
> all the LO injections to be on the highside, but CW to be only on LSB so
> it runs CW on LSB on all bands. With solid state switching some of the
> anomalies were taken out in the control logic that are not so easily
> changed in the Corsairs because mode switching is a ganged switch.
>
> 73, Jerry, K0CQ
>
> On 4/16/2011 1:00 PM, Steve Hunt wrote:
>> Jerry,
>>
>> I never understood that piece of Ham folklore, or should it be "Ham Myth" :)
>>
>> In a mixing arrangement comprising a 9MHz IF and a 5-5.5MHz LO, designed
>> to cover 20m/75m, there is *NO* sideband inversion between the IF and
>> the RF. A USB signal generated at the 9MHz IF would become a USB signal
>> on 20m and also a *USB* signal on 80m.
>>
>> So, simplification of the sideband generation or detection for that
>> simple mixing arrangement cannot be an explanation for the sideband
>> convention we have today.
>>
>> 73,
>> Steve G3TXQ
>>
>>
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