Is it normal for the results of a 10 MHz Spectrum Scan to omit noise found in a 20 MHz Spectrum Scan?
Not at all if you were capturing the spectrum with a former spectrum analyzer.
Are you able to repeat the same result, always?
Hello Daniel
I am running the built in Spectrum Analyzer on the 450i.
Yes. I can repeat the scans and get the same results that show differences between the 10MHz and the 20 MHz.
I have done this repeatedly Back-To-Back. (My OCD is showing a bit I know).
Furthermore I make sure the the AP not transmitting during the analysis.
Is the normal?
Stay Safe
Not for me, but then, I'm not operating any 900MHz Cambium equipment in the field.
It could be some kind of artifact not representing air noise but electronic intermodulation. Or and effect of the FFT windowing. Maybe some 900MHz techie could chime in and give some advice!
@LostInTheTrees wrote:Is it normal for the results of a 10 MHz Spectrum Scan to omit noise found in a 20 MHz Spectrum Scan?
LostInTheTrees,
Spectrum Analyzers detect the peak power for across that channel banwidth. So it is normal for 20 MHz to detect more interferers than 10 MHz. This is due to each receiver accepting power with a bigger filter. If the interferere is only 1 MHz for example, it will show for more readings in 20 MHz than 10 MHz.
For best most granular spectrum analyzer it is recommended running at the lowest supported channel bandwidth.
Charlie
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Charlie
Thanks for the information.
"For best most granular spectrum analyzer it is recommended running at the lowest supported channel bandwidth. "
So are you saying to select the smallest channel bandwidth to operate the link in or run the analyzer in?
And would noise seen in the 20MHz and not in the 10MHz affect a cambium link running in a 10MHz?
Stay Safe
@LostInTheTrees wrote:Charlie
Thanks for the information.
"For best most granular spectrum analyzer it is recommended running at the lowest supported channel bandwidth. "
So are you saying to select the smallest channel bandwidth to operate the link in or run the analyzer in?
And would noise seen in the 20MHz and not in the 10MHz affect a cambium link running in a 10MHz?
Stay Safe
He's saying that if you want to see a more detailed/granular picture from the spectrum analyzer, that you should use a smaller channel width (5MHz is the smallest) for your SA. If you're doing an SA from an AP, you'll need to actually change the channel width on the AP, save, reboot, and then run an SA. I'd recommend running a 5MHz channel width to get the most detail. At the top of the SA it will say 'Reciever Channel Bandwidth: 5MHz'. If you're using an SM to scan OR you're having the AP do a timed SM scan, you can set the 'SM scanning bandwidth' on the SA tab.
As far as your question 'And would noise seen in the 20MHz and not in the 10MHz affect a cambium link running in a 10MHz?'... it depends... you might want to run a scan over a longer period of time using a 10 or 5mhz scan width. It may be that because scanning using a 10 or 5mhz channel width takes longer then using a 20mhz width, that perhaps if you did a short scan using 20mhz, the SA caught a burst of energy... while a 10/5 scan possibly missed that burst of energy and might take a longer scan to finally catch that burst... but where the burst occures will be more accurate then a 20mhz SA and will give you a better idea of of a safe place to put your AP's center frequency.
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