Finding interference source

Products PMP
1

I have a 900 MHz Omnidirectional AP that has recently had 2/3 of the subscribers drop off.

It appears that the noise floor has risen as only folks w/ -60 dBm or better are getting registered.

I’m wondering how we can find the source of the interference? Obviously the omnidirectional antenna makes it a more difficult proposition than it would be w/ 6 x 60* sectors…

(BTW, the spec analysis shows noise across the whole band…)

Thanks in advance all

2

This isn’t cheep, but it will find the problem.

http://www.cognio.com/solutions_rfid.html

3

You can rent a professional spectrum analayser like an Anritsu, and use a directional antenna (18dBi Yagi).

Use triangulation to locate the source by starting at your AP’s, find the general direction - drive that way for a while, take another measurement, drive that way for a while, etc, etc. Eventually you will arrive at the source. Leave your AP down while you do this on a Sunday.

You can rent equipment here: http://www.electrorent.com/index.aspx

I assume that your AP and all SM’s are on 7.3.6?

I have all SM’s allowed to scan all frequencies for just this reason. We had a helluva time finding a clean frequency to use. I started at the bottom, and start working my way up until everyone can register. I have had to move freq’s twice.

Oh, the joys of Unlicensed Spectrum!!!

4

Just called Electrocomm to see what the cost is.

The Anritsu/Wiltron MS2721A 100kHz-7.1GHz Handheld Spectrum Analyzer for 7 days is 632.00 and for 30 days is 842.00 (bring your own antenna). Since they cost some rediculous $$$ to buy, renting seems to be the smarter way to go.

I think we are going to rent one anddo some baseline testing while the network is running well.

5

Thanks for the insight!

I figured it would come down to drive testing… I used to work at a GSM cellular provider that was forever drive testing the PCS side of things…

I wonder if you can just modify the GSM gear & software w/ the Canopy specs… hrmmmm.

6

Yes !!! Isn’t it wonderful!!!. Unlicensed spectrum!!! For us the users is a constant worry in the back of our head. For the manufacturer is a heaven. They show you the numbers…it’s so cheap…you’ll have 6 months ROI. But then…BOOM!! interference. We are on this building, where everytime we have to get to the roof to make repairs they’ll the security at the building would almost take blood samples from us, do cavity search, and everything to make sure we are authorized to access the rooftop. We been there for almost 7 years. One day all our customers were down, when we get up there, we found that somebody new had manage to smugle a 6 foot 5.7 ghz dish up there, and fired it up right next to our canopies. How did he manage to do that? Anyway, it’s been fixed now.

7

Has anyone seen or tried one of these. Spectran 6060 or 6080?

http://www.aaronia.de/

Look to be very useful for us (models 6060 or 6080), Good price 799 or 999 euros. They will ship to the USA (I have emailed them).

This guy sells them here (in the USA)

http://www.lessemf.com/rf.html#135

Model 6060 for $1200.

What do you think? Could be sweet compared to $650 to $850 for one time rental.

8

Very Very cool

Thanks for the link!

9

Jerry, are you going to get one?

10

It’s on the wish list…

Maybe a month or two. Need a couple more 600/mo cutomers…