Folks,
I have been meaning to try such an idea out for a while as a Friday
night (less than four hours build time!) project.
I have a Racal 100mW drive source that I can set to CW and pad down
to drive an SBL-1 as the mixer. SpectrumLab running on one PC will
generate the two or three tones required. WaveSpectra or some such
FFT program (any other suggestions?) should give a display on the other.
I wonder if useful results will be forthcoming? We shall see...
Regards.
Mark.
-------------------------------------------------
At 15:59 11/08/2006, Bill Fuqua wrote:
>An oscillator, good mixer and a sound card running FFT should work. You
>want to mix the RF down to around 10 kHz ( center of the sound card
>frequency range) and observe sidebands around it.
>
>You can use a sound card to also produce the two tone test signal to insert
>into the SSB exciter.
>
>73
>Bill wa4lav
>
>
>
>At 10:43 AM 8/11/2006 -0400, Martin AA6E wrote:
> >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
> > > _______________________________________________
> > > Amps mailing list
> > > Amps@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/amps
> > >
> >
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*******************************************
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E-mail: g4fph@mjha.co.uk
Current web pages at: www.g4fph.net
Old web pages at: www.qsl.net/g4fph
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