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Re: [Amps] Tiny SA ultra, part 2

Subject: Re: [Amps] Tiny SA ultra, part 2
From: Jim Brown <>
Date: Sun, 7 May 2023 21:12:22 -0700
List-post: <>
On 5/5/2023 9:28 AM, jim.thom wrote:
Several folks told me that the Tiny SA was useless for IMD testing, due
to it's 3 khz resolution.   Apparently somebody listened, and the newer /
bigger version, with it's 200 hz resolution, should fare better.

That's quite coarse. The Elecraft P3 can get down to a few Hz; the SVGA card, which does a higher res FFT of the same data, gets down to fractional Hz. This is the sort of resolution needed to measure transmitted bandwidth.

Some measurements I did about ten years ago are shown in these pdf files. The first, for a talk by Elecraft engineer Bob Wolbert, K6XX, was done before the SVGA card was developed.

The second file, which uses Power Point as a convenient means of showing graphical data, was not intended for presentation to a club or at an event. The measurement method is mostly described with text slides.

The P3, with or without the SVGA board, measures 100 dB of dynamic range, but can display only 80 dB on the screen at a time. It turns out that 80 dB is more than enough for even the best rigs I've measured, but if a cleaner rig showed up (or perhaps with Pure Signal), the bottom 20 dB could be displayed simply by changing the zero reference for the display.

The various SDRs shown in the talk and text pdfs on chasing RFI by studying their spectra, mostly have very good frequency resolution. NR0V, who authored both Pure Signal and computer software for ANAN radios, told me that the little 10W Anan rig is good for fractional Hz  Text  Slide show

I used the P3 and SVGA board because they could do the job and I had them. Both are discontinued by Elecraft. If I were doing those measurements today, I'd probably use the ANAN.

I own both HP8590D and Rigol spectrum analyzers. Their frequency resolution specs are comparable, MUCH to wide (at least two orders of magnitude) for transmitted bandwidth measurements of transmission modes used by hams.

73, Jim K9YC

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