A strong signal
> adjacent channel could reduce receiver gain. Anyone who
> tests receivers knows about being misled by things like
> that.
Yes that could happen just as it can with a spectrum analyzer.
That's why the main signal is often notched down to look at low level
products without overloading effectively increasing the dynamic range of the
analyzer.
>
> I'd like to see how it works on a half dozen common
> receivers both over the air and on loads. One major
> difference between analyzers and receivers is ingress into
> the system from power mains and such. I'm sure a good
> protocol and guidelines could be developed and it would be
> useful for something in most cases.
>
> I'm almost leaning more towards AGC off, an attenuator, and
> a sound card program. With careful adjustment it might be
> possible to get 50dB or more DR and use a voice signal.
>
> What spectrum programs are around?
I haven't played with any of the spectrum programs as of yet. That's on my
list for "one day". Maybe some of the others have experience there.
With voice the problem will be catching the particular products generated at
the right time. Maybe some of the programs are fast enough to provide real
time analyses.
The other problem with trying to run a spectrum from the receiver audio with
voice modulation is that many of the products 3rd, 5th, 7th etc can fall on
the same frequency and be indistinguishable from one another. As discussed
before, there are many combinations of frequencies available to generate the
IM products so for example a 3rd and 5th order product could be generated on
the same frequency by two different sets of modulating frequencies, one set
generating a 3rd order product falling on say 1.5 KHz and a different set of
frequencies generating a 5th order product that also falls at 1.5 KHz.
73
Gary K4FMX
>
> 73 Tom
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