Bill,
I've wondered about this, too. The lab method is to use a high-priced
spectrum analyzer, but couldn't you do something useful with a soundcard
based spectrum analyzer? You would need to have a linear detector and a
two-tone audio source. This would be similar to the IMD measurement you
get with a PSK31 monitor. The trouble is you need pretty good dynamic
range to measure a healthy system.
You could check the boxes being sold by www.cleanrf.com as described in
the latest CQ. They let you look at "linearity" on a scope. My take is
that you will only catch gross non-linearity (overdrive), but you
wouldn't get quantitative IMD numbers with this approach.
73 Martin AA6E
Bill Turner wrote:
> Is there a simple procedure one can use for checking the IMD of an
> amplifier? Frankly, it's something I have never tested myself, instead
> just keeping the amp tuned correctly and underdriving when using SSB.
> I've never gotten any complaints of splatter so I think it's under
> control. Since I do mostly RTTY and some CW it has not been an issue
> but I would like to be able to check it.
>
> Any recommended reading on the issue?
>
> Bill, W6WRT
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