Again we agree.... although I WAS under the impression that 24/30 was considered acceptable for amateur equipment. A quick Google reveals that there is no apparent requirement beyond the spur suppression that you mention.
It seems that 24/30 is commonly accepted and often violated in commercial amateur equipment. I would be interested to see the mil spec.
Thanks for that! I learned something again.
Warren Allgyer - 9V1TD
--- In firstname.lastname@example.org, Jack Smith <Jack.Smith@...> wrote:
> Yes, I believe that is correct, except that I would question 24/30 dB
> down as "acceptable" for an exciter. I don't believe there is a minimum
> specification for 3rd order IMD for amateur band equipment other than
> whatever may be implied by the 20 dB down bandwidth rules and the "out
> of band" emissions, but except for QRP equipment I would hope for better
> performance than 24/30 dB suppression.
> Jack K8ZOA
> On 6/14/2013 6:20 PM, warrenallgyer wrote:
> > So the answer to the question as posed is:
> > 1) Modulate the transmitter with two, equal level audio tones well
> > inside the SSB bandpass.
> > 2) Display the resulting RF signal on the spectrum analyzer with an
> > RBW setting low enough to resolve the two resulting audio peaks.
> > 3) Measure the relative level of the next two peaks on either side of
> > the center audio peaks. These are the result of sum and difference
> > products of the original two tones.
> > 4) The level of these products must be 24 dB below the main peaks in
> > order to comply with accepted IMD3 levels.
> > 5) 24 dB below the two main peaks is, by definition, 30 dB below the
> > PEP capability of the transmitter at this modulation level.
> > Warren Allgyer - 9V1TD