RIGOL DSA815 Spectrum Analyzer - How To Caprute An Intermittent Signal - Page 1
Forum section: electronics / testgear

author: Steve Wayne
author_rank: Contributor
timestamp: December 14, 2015, 10:16:29 pm
content: Help would be greatly appreciated from those with knowledge on how to capture an intermittent signal on a RIGOL DSA815 Spectrum Analyzer. I cannot seem to find a trigger function or mode enabling the unit to stop on, and/or freeze & record an intermittent signal frequency and amplitude. The roughly 430 MHz signal lasts for around 500ms and occurs between appropriately every 1-2 minutes. Mahalo,

author: KD0RC
author_rank: Regular Contributor
timestamp: December 15, 2015, 02:26:20 am
content: Hi Steve, I often use the Max Hold trace type. I set one trace to Max Hold and the other to Clear Write so that I can see what is going on. You can also use the single in the Sweep/Trig menu, but it could be hard to time it right to capture the desired signal popping up. After the Max Hold grabs the shot you want, you can change the trace type to Freeze and it will hold it there without subsequent traces influencing the capture. Go to the Trace/P/F menu and select the Tace Type there.Hope that helps.Len

author: Richard Head
author_rank: Frequent Contributor
timestamp: December 15, 2015, 05:57:41 am
content: A sweeping spectrum analyser cannot capture short bursts of RF. You need a realtime spectrum analyser. They are quite amazing devices and I yearn for one.

author: Pinkus
author_rank: Frequent Contributor
timestamp: December 15, 2015, 10:43:48 am
content: Quote from: Richard Head on December 15, 2015, 05:57:41 amGenerally you are right Richard, but I would not call a 500ms long signal a "short burst". If you set the analyzer to 430 Mhz center and a span of 5 Mhz at 30 Khz RBW you will have a 10ms sweep time - this is quick enough to catch the signal at the first occurance. Switch on 'Max hold' as Len suggests and you are all set.Another solution for short or seldom occuring signals: use the pass/fail mode. In this case the signal you are looking for shall be the strongest of other possible signals of the same frequency. Then set a pass/fail limit (e.g. -60dB for 429 to 431 Mhz - the analyzer will draw a line). Whenever a signal 'hit' the line, the analyzer beeps and stops automatically (if you selected these two options).

author: Richard Head
author_rank: Frequent Contributor
timestamp: December 15, 2015, 01:43:05 pm
content: PinkusYes, I agree. 500ms is possibly workable like you say. I'm not sure if my Advantest can capture that though. Those realtime spectrum analysers are amazing. So powerful when it comes to signal analysis.I wonder if Santa could bring me one this year.

author: gm0otb
author_rank: Contributor
timestamp: December 15, 2015, 02:28:53 pm
content: Hi Steve,Crude I know, but you could try using the RTL dongle as it can monitor up to 3.2Mhz at a time in a single chunk? (Real time!) provided you know the rough frequency.Probably use some SDR software as the spectrum analyzer software for the RTL dongle does a single sweep.As mentioned Max hold is your best bet on the DSA815.Ray.

author: cncjerry
author_rank: Unknown
timestamp: December 16, 2015, 09:47:13 am
content: I have an advantest SA r3131a as well as an HP 8568b. I think both can capture that signal pretty easily. Max hold is the way to go. If you have a pulse generator you could experiment with it first before looking at the live signal.

author: Steve Wayne
author_rank: Contributor
timestamp: May 31, 2016, 07:40:18 pm
content: Thanks everyone. Your suggestions were quite helpful.