Hey everybody, we’ve been having weird fluxuations in the Signal/Noise readings within Cacti for one of our 20MB BH’s.
The BH is 12.85 miles on Hardware Scheduling, with a RSSI of 1050ish and a jitter of 7-8 and a Power level of -58.
I watched the status page for a bit and monitored the signal and noise the RSSI went from 1050 up 1088 and down to 1008, and the jiter would from 5-9 and the Power level would go from -56 to -59.
There are no errors (CRC or CarSense) and the link is 100% down and 99% up, and the speeds are pretty even (about 7Mb down and 6.3Mb up)
Here’s a snap of what I’m seeing in Catci:
Anybody know what could be causing this?
Cheers
Brad
i wish i could figure out my cacti ez to get graphs 
That looks like interference adaptation.
You must have a noisy neighbor in that band
Jerry
would noise not show up on the jitter as well? Cause it doesn’t seem to go anyhigher then 9.
a jitter of 9 is pretty high. I dispatch a tech if it stays above 7ish
This is for a 20MB BH not a client so a jitter of 9 is pretty normal. Sorry if I didn’t make myself clear on that.
I would agree with Vince, 9 on a BH is high in my books… but if you are getting the throughtput and link is stable (reg and re-reg) then it should be ok.
I have seen RSSI flutuate in Alignment and status page… I don’t pay much notice to it anymore…
There is eno0ugh margin there to handle some interference without too much effect on the Jitter.
9 is a tad high, but as mentioned if you are getting 100% both ways then you are probably OK.
Hmmm…alway’s thought that a jiter of 8 on BH20 was pretty standard.
So what’s a respecticle jitter then for lets say a 10mile link? 4-5?
I believe 9 is OK with 20 Mbps modulation. I’m sure the acceptable numbers are in the manual somewhere.
FWIW looking at the last week of data the jitter on our main BH20 [P9] with HW scheduling @ 11.7 miles the average is 6.8 with a rare spike to 9.
Downlink RATE: 4169216 bps
Uplink RATE: 9785344 bps
Our tower to tower BH20 [P8] with SW scheduling @ .12 miles averages a jitter of 8 with the occasional 9 or 10.
Downlink RATE: 10487808 bps
Uplink RATE: 4096000 bps
Both pass at 100% both ways all the time.
We aim for jitter of 3/4… but use the link efficiency as the true decider of if the link should be commissioned.
I read the Canopy article on RSSI and jitter. It says that a 10Mb BH will generally have a jitter from 5 to 15 but a sustained jitter of 9 or higher is bad. And a 20Mb BH will also have a jitter from 5 to 15 with acceptable jitter vaules anywhere within that range. So if you have a jitter of 3 or 4 on a 20Mb BH you got a kick’in link!!