[time-nuts] Double balanced mixer question

[Richard (Rick) Karlquist]

A DBM inherently does harmonic mixing...at no
extra charge :-).  In this case, the third
harmonic of the LO mixes with the RF and
you get 15.0 MHz - 5.000001 MHz = 9.999999 MHz.
This signal be down 20 log N, where N=3, IOW,
-9.5dB.  There is nothing you can do about this
as long as you use a DBM.

As has already been pointed out, an RF analog
multiplier is the only work around.  Depending
on how ideal it is, and how much you back off
the drive level, you will get some amount of
9.999999 MHz, but it should be considerably
less if you play your cards right.

You could also build a frequency tripler to
change 5 MHz into 15 MHz.  That will "eliminate"
the problem to the extent that you filter the
tripler output to eliminate 5 MHz spurs.  There
is no limit to how much suppression you can
get since it's just more filtering.

Rick N6RK

On 7/23/2020 11:01 AM, cdelect at juno.com wrote:
> Hi,
> 
> I'm feeding 5.0 MHZ and 5.000001MHz into an HP10514A mixer.
> 
> A buffer and a 12dB attenuator feed each input and a 50 Ohm buffer amp
> (10Mhz) is on the output.
> 
> I get a nice sine output but get the 1Hz as amplitude variations.
> 
> Playing with input levels I can minimize the variations but the best I
> can get is a 3.2 V P-P with a .4 V P-P amplitude modulation.
> 
> Are there mixer schemes I can use that will eliminate the amplitude
> variations?
> 
> Cheers,
> 
> Corby
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