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colebert
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802.11n PTP links going batsh*t crazy

Mon May 24, 2010 1:13 pm

OK, I have a set of PTP links I've been testing for a few months and they have been pretty solid. I got them all going well, or so I thought.

For the last six hours they have basically been going crazy and it is all related to signal strength.

Let me just say that all my links have clear LOS/fresnel and are "big boy" Andrew ptp waveguide antennas. Currently the weather is perfect. Clear skies, 68 to 72 degrees F, no wind, 29.99 barometric pressure, 94-100% humidity, 66 degree dew point, no fog. But my signal strength is going haywire. Torrential rains, crazy fog and ice storms have never bothered my links like this.

Link #1 (26 miles): Normally -55 to -60 strength is bouncing around from -75 to -90 and above and dropping out even at MCS0. CCQ normally 95-100% is now in the 40s with no traffic passing.

I have about 7 other PtP links that run back to back from each other and span about 150 miles worth of ground. They are all sucking for signal strength, at least 10 to 20 db off their normal readings which usually vary depending on link from -45 to -60 (at worst.) Tonight everything is just taking an nose dive and I don't know why.

I'm use RB411AH boards for every link, SR71-15 cards at default power, Laird pigtails, ROS 5.0 beta2, 5.7-5.8GHz, and bandpass filters. The links all run stable at MCS7 but I also have MCS6 and MCS0 enabled for fall back but signal strength on some links are so bad that MCS0 isn't working.

Remember, this isn't 7 links running out of the same place. Each link is in a different location and covers completely different geographic areas, runs between 18 and 36 miles, and is experiencing severely impacted signal strength and CCQ. I've tried rebooting and it hasn't helped (duh.)

I'm thinking weather is causing this but I don't know why ostensibly perfect conditions are resulting in all these different links to wig out.

Ideas?

BTW, this would be a great time to have that power offset issue fixed in ROS for the SR71-15 so I could bring the full power of these cards to bear on my problem! Days like today make me appreciate my old XR5s.
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popcorrin
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Re: 802.11n PTP links going batsh*t crazy

Tue May 25, 2010 3:46 am

I've heard of exceptional weather circumstances causing a solid link to take a nosedive but it's hard to believe that it would cause 7 links over a stretch of 150 miles to crap out.
 
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colebert
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Re: 802.11n PTP links going batsh*t crazy

Tue May 25, 2010 5:45 am

Well about 3 links crapped out to the point they wouldn't stay at MCS0, had CCQ of between 15 and 30, and registered a total throughput of about 5120bps or something. It was pretty bad.

But every link was off from 20 to 40 dbm. A couple that have really high SNR (70+) continued to work but the ones that only had a 50+ were really compromised.

They are all back to normal and working just fine. The only thing that changed between when they were wigging out and when they came back to their sense was the humidity came down from close to 100% to about 70%. But it regularly gets that humid here and I haven't seen ill effects like this before.

It's really confusing because I've got really high end dishes equipment here, clear fresnels, and pretty good fade margins but this anomoly totally wiped me out. Maybe this is just one of those days that the Motorola LinkPlanner assumes you'll have even though all the numbers say it should be 100% uptime...?
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changeip
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Re: 802.11n PTP links going batsh*t crazy

Tue May 25, 2010 8:55 am

so that rules out hardware issues if it just came back to life, correct? i wonder if a pure A link would have been affected the same way.
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0ldman
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Re: 802.11n PTP links going batsh*t crazy

Tue May 25, 2010 7:58 pm

I've had some odd issues lately myself.

5GHz shot just crapped out, -77 signal just went off the grid.

changed channels, got it limping through, went back to the original channel, -77 again. About 10 minutes worth of trouble, then it was just gone.
 
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tgrand
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Re: 802.11n PTP links going batsh*t crazy

Wed May 26, 2010 3:57 am

SOLAR BLAST: A magnetic filament on the sun erupted yesterday, May 24th, and the blast hurled a coronal mass ejection (CME) in the general direction of Earth. NASA's Solar Dynamics Observatory recorded the action around the blast site in 10xHDTV resolution:

http://www.spaceweather.com

Possibility.....
 
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tgrand
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Re: 802.11n PTP links going batsh*t crazy

Wed May 26, 2010 4:03 am

Problem should get somewhat better come night fall.

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