Phase noise...separating wheat and chaff? - Page 1
Forum section: electronics / rf-microwave

author: 0culus
author_rank: Super Contributor
timestamp: August 03, 2019, 03:44:31 am
content: So I finally got me a GPIB adapter, so I've been playing with the KE5FX utilities using my 8566A and different signal generators. Having already read the app note, I'm still unsure of whether I'm seeing bullshit or not. Attached is a phase noise plot, at 4 different clipping settings, of a 500 MHz carrier from my 8640B sig gen.First of all, my gut feeling is that those super low dips are not real. Pretty sure -170 dBc/Hz is well below what the 66A is capable of based on reading spec sheets. Also, the clipping settings appear to be doing very little other than shifting the plot around.Any tips/suggestions/other resources I perhaps haven't found?Thanks!

author: 0culus
author_rank: Super Contributor
timestamp: August 03, 2019, 04:50:04 am
content: ...and those gigantic peaks don't look normal either.

author: KE5FX
author_rank: Super Contributor
timestamp: August 03, 2019, 05:37:55 am
content: The peaks are spurs; you'd normally hit ctrl-s to remove those from the plot. The divots aren't normal, and could be a problem with the analyzer itself. Likewise, changing the carrier clipping really shouldn't move the whole plot around like that.Questions:- Can your 8566A pass its auto-align routine (Recall-8, adjust amptd cal, Recall-9, adjust freq zero, Shift-W, then shift-w to check the results versus the manual)?- What happens when you measure the analyzer's own calibrator? Do you get a baseline plot similar to the ones in the Composite Noise Baseline Plots subdirectory under the GPIB Toolkit's installation folder?

author: 0culus
author_rank: Super Contributor
timestamp: August 03, 2019, 06:20:56 am
content: Quote from: KE5FX on August 03, 2019, 05:37:55 amAs to your first query, yes it does. All the values appear within nominal ranges.However, I cannot get either the 66A or my 68B to communicate over HP-IB now...I suspect it's just windows being a pile of crap as always though. It gets into loops where your GPIB configurator app just launches and crashes after "not responding" for about 5 seconds.

author: 0culus
author_rank: Super Contributor
timestamp: August 04, 2019, 01:43:27 am
content: Got things working again. Here's the pn plot with spur reduction enabled and using the 8566A cal signal.

author: 0culus
author_rank: Super Contributor
timestamp: August 04, 2019, 01:57:51 am
content: Additional tests:

author: 0culus
author_rank: Super Contributor
timestamp: August 04, 2019, 03:11:30 am
content: I can't seem to do a noise floor test like one of the examples. If 0 dB atten is force, it just stops in the middle of the procedure.

author: coppercone2
author_rank: Super Contributor
timestamp: August 04, 2019, 03:17:30 am
content: i shudder to think what I will get when I try to calibrate/verify the equipment I have10 years of work ?

author: KE5FX
author_rank: Super Contributor
timestamp: August 04, 2019, 03:44:32 am
content: Quote from: 0culus on August 04, 2019, 03:11:30 amDefinitely something wrong there, but it's hard to say what. Send me that .PNP file, would you?

author: 0culus
author_rank: Super Contributor
timestamp: August 04, 2019, 03:55:29 am
content: Quote from: KE5FX on August 04, 2019, 03:44:32 amSent.