In article ,
says...

The W7ZOI homebrew spectrum analyzer article is not to be missed:

http://www.qsl.net/n9zia/wireless/pdf/9808035.pdf (part 1)
http://www.qsl.net/n9zia/wireless/pdf/9809037.pdf (part 2)

You'll find this design vastly superior to the "poor man's spectrum
analyzer" projects out there that are based on CATV tuners.

The W7ZOI project is very interesting. I'm interested in what ways you think
it's superior to the poor man's spectrum analysers based on CATV tuners? The
latter surely have greater frequency coverage. But in what ways are they
inferior and can you quantify it?

Apart from what Ian said, it's also really important to have a stable
LO. If you don't -- i.e., you're relying on an inadequately-stabilized
cable TV tuner -- you can only tell if a signal is present or absent.
You can't tell much about its stability and noise level, or look for
close-in IMD products. Narrow resolution bandwidths require stable LOs.

I haven't used a W7ZOI analyzer myself, but it ought to be at least an
order of magnitude more stable than any CATV implementation. It would
indeed be interesting to see a spec-for-spec comparison between the two.

Either way, they make great educational projects.

-- jm

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