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RobClem
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65Km Link - Problem

Sun Oct 08, 2006 9:45 pm

Hi,

I've just install a 65Km link using a pair of 32.5dbi dishes at each end of the link - one end of the link is temporarily using an RB112 with an R52 mini=pci card runing in station mode. The other end of the link is using a wrap board with an SR5 card and also has a CM9 connected to a Sector ANtenna for my clients.

I have a signal dependnig on the channel I select of around -78 but I know this can be improved with a little more alignment. I am running Nstreme and Best fit Framer Policy - both ends are hard set to 6Mb for now.

The problem I have is when I run a BTest from the SR5 end of the link in Send mode I get around 2Mb throughput and no dropped packets - when I run a Btest in Receive mode the link drops totally which is the bit I am trying to figure out right now.

I think it has something to do with the 400Mw SR5 card I am using at one end of the link - can anyone offer any advice please as I need to sort this fault before I proceed with fine tuning.

Also - can anyone offer suggestions/tips for optimal settings on a long link like this.

thanks

Rob
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ghmorris
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Mon Oct 09, 2006 12:29 am

If the link is dropping you probably have an interference problem that MT is not displaying. Happens all the time.

Put SR5s both ends for starters and use a 532 at both ends. The 112 is not ideal.

Make sure polling is turned on in Nstreme, and while you have the 112 on line turn off link aggregation. Too much load.

Depending on where you are, your antenna choice is very marginal. -78 could well turn into -100 in a split second, too fast for you to detect in fact. We use 12' dishes for 30 mile links, but we are in an ugly area for fade and need 50dB plus to run successfully.

If you want to run through this, send me your phone number to ghmorris at candlelight.ca.

We do tons of long-haul links.

Regards
George
 
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BrianHiggins
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Wed Oct 11, 2006 6:57 am

If the link is dropping you probably have an interference problem that MT is not displaying. Happens all the time.

Put SR5s both ends for starters and use a 532 at both ends. The 112 is not ideal.

Make sure polling is turned on in Nstreme, and while you have the 112 on line turn off link aggregation. Too much load.

Depending on where you are, your antenna choice is very marginal. -78 could well turn into -100 in a split second, too fast for you to detect in fact. We use 12' dishes for 30 mile links, but we are in an ugly area for fade and need 50dB plus to run successfully.

If you want to run through this, send me your phone number to ghmorris at candlelight.ca.

We do tons of long-haul links.

Regards
George
12' dishes?? we have a few 19 mi links running with 3ft dishes and CM9 radio's with signal's of -61... we had SR5s in there, the signal was around -40, but very flakey. I suspect we just couldn't power the radios correctly (SR5 and CM9 at same time)...

on another note, as a WISP, why in the world would you have a picture of a bunch of lightning hitting the city on the front page of your website??? you've never heard of bad karma before have you....
 
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ghmorris
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Wed Oct 11, 2006 2:34 pm

We're in the text books for some of the highest fade 6 gig long-line shots in North America. We need way over 50dB of fade margin to survive on 30 mile links in early summer and mid autumn.

In fact, 12' dishes with frequency, polarity and spatial diversity will just barely yield 99.9997% uptime which is crappy for a telco long-haul link. OTOH, for our use that reliability is pretty nice, so we now use 6 gig licensed for our longest backhauls.

I still have a couple of 35-milers left and we run them at -44 to get enough fade margin for reasonable reliability.

I wish MT would give us diversity so we could set up spatial diversity on some longer shots...

That picture is an in joke. We want all the lightning to whack Toronto and leave us alone. Doesn't happen tho, we get more than our share...

George
 
variable
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Thu Oct 12, 2006 1:58 am

what causes that much fade? the rain?
 
jo2jo
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Thu Oct 12, 2006 7:51 pm

wooo i would assume that a big issue here could be that he is using a low memory / low cpu rb112 i know its temporary but simply using nstream on a 112 almost over loads it...BW tests generated on teh RB takes up A TON of resources.

either try upgrading toa 532 or better or do the bandwidth tests THROUGH the routers and not from each (i.e a computer on each side)
 
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ghmorris
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Fri Oct 13, 2006 1:14 am

what causes that much fade? the rain?
Thermal effects.

Lots of lakes, exposed granite and trees on the path. All of them heat and cool at different rates. We get lots of ducting as well. Seems like sometimes the signal goes everywhere except where its supposed to.

Wild swings from -30 to -100 or worse every few minutes before dawn and at dusk.

Great sport (if you don't have to explain to customers why their service is flaky!)!!

George
 
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BrianHiggins
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Sat Oct 14, 2006 4:15 am

we get some thermal fade, but not at our towers or our backhaul links (at least nothing significant) where we see some issues is our CPE's, they are much lower to the ground and often shooting over the roof's of customers. on a real hot day we see the signal's jump (yes, sometimes they actually get better) or drop, as much as 8 db, but no more then that... we install down to a -80 signal, gives us a full 10db of operational fade, anyone that can't maintain a -80 or stronger, we put bigger antenna's on, until they do.

nice to see you've got a sense of humor about the lightning :)
 
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znet
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Microwave Fade

Sun Oct 15, 2006 8:10 am

Hard to explain to my 'management' that fade situation you have there George. When I get asked 'What happened last nite' after they get an onslaught of alarms that they foist on themselves by receiving them on their Blackberry's, :roll: I remind them 'Its microwave fade season again'. Your situation would put them over the edge! :lol: I take 30db fades on 30mi paths without disconnects and feel good about it. Its amazing the differenct scenarios that can cause the inversion fades. My situation is radiational cooling and humidity. Happens every change of season. So far my best solution has been diversity in every way possible.

So, what do you think happens to the microwave when you get cool nights after hot and humid days? Does the wave sink or lift? I have my gut feel on this, but you seem to take the cake on this topic, so which way does it go?

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