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spectrum analyzer question

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Posts: 522

« on: March 09, 2020, 02:23:55 PM »

Why is it that when I use my HP-ESA 4411 spectrum analyzer to look at two tone signals from a SSB transmitter I can get it to show the nice clean two peaks with twenty or thirty Db skirts like the pictures that I see on line and in the ARRL handbook?  I can bring the span out to 20 or 50 kHz and see the two peaks but the skirts are super wide with maybe a gradual sloping giving a display that looks like two mountains. Tried different tones and all that sort of stuff. May have tried bring bandwidth down to 10 kHz or so but just not getting that pretty waveform that I would expect.
Been using this analyzer for years to look at things like harmonics, noise and occupied bandwidth in commercial stuff but as of late want to look at the level of intermod in SSB transmitters.
Was wondering if itís because I need a better level of performance that whatís in the ESA? Have been looking at maybe picking up a surplus HP-3585 thinking maybe thatís a better preforming box for narrow bandwidth work? But wanted to see what others think.
Maybe the SSB transmitter I am using has that much intermod? Do you have to do these test at stupid low power levels or what?


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« Reply #1 on: March 09, 2020, 02:59:44 PM »

You're probably at the limit of your resolution bandwidth. I believe the "stock" ResBW for that SA is 100kHz. Optional filters are available that can bring that down to probably as little as 1Hz. Got a manual for it?


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« Reply #2 on: March 14, 2020, 09:52:10 AM »

Don't know about the "B", but the "A"s RBW is 1Kc minimum.   Too wide for two tone measurements, I think.   If the sweep speed is adjustable perhaps slowing it down might might improve things a bit.

Mike KE0ZU

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