In message <19970617021628.AAD16467@fred> w8jitom@postoffice.worldnet.att.net
writes:
> > From: Joe Fitzgerald <jfitz@albany.net>
> > w8jitom@postoffice.worldnet.att.net wrote:
>
> > Tom, what is your opinion of generating two audio tones say, 2 Khz apart
> > and feeding them into the mike of an ssb transmitter?
> I don't think much of that method, because the exciter always has
> IMD distortion and less than perfect sideband and carrier
> suppression. Most tube PA's will go far beyond what a modern solid
> state rig will do in IMD performance.
The question of which is the best method must revolve around whether
you are attempting to measure the IMD of the total system or just of
the external rf amplifier alone. Measuring the data to print in an
amplifier spec sheet is a different exercise from performing a health
check on your overall station, and it will call for different methods.
A difficulty with the two-exciter method will be coupling the two
high level drive sources in such a way that the generators are still
sufficiently mutually isolated so as not to introduce IMD themselves
and make the measurements meaningless. Coupling two low level audio
sources with minimal mutual coupling is a more straight forward task.
Regards,
--
Tony - G3SKR / W2TG email: tgold@panix.com
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