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5ghz question, trees

Posted: Tue Apr 03, 2007 5:38 pm
by jo2jo
I hate to say it, but i have no experience with 5ghz ptp over distance.

I've done 2.4, and 900 with no issues. But I have a .75 mile link (1.2km) link between a 20 story building and a 4 1/2 story building. Its right through the top of a leafy oak tree.

I know there are alot of 2.4 APs around (consumer) so i wanted to use 5ghz, for the improved latency and Bandwithd, and less interfearence (right?)

I wanted to use a rootenna on one end, which will be going through a thin glass window, no lead, then the tree and directly to the other roof top.

I wanted to use R52s if possible.

any input before i get out there and waste time potentially? im not a fool, i know u guys cant give me numbers or anything specific about the link quality, but what i'm looking for is some kind of input on 5ghz through the top of a tree.....for all i know that may be a BIG no-no.

this is not a serious link, only 2-3mbit for like 10 very casual web browsers..and maybe a few low low use voip lines.


Thanks for the help.

Posted: Thu Apr 05, 2007 4:40 am
by Chipi
Mesh system work in 5.8 ghz, with Nlos (Trees, buildings, etc...) but with more power radios, like 500 mw and better sensitive cards...

I suppose that the R52 is not a good card for your situation....

Regards

Posted: Thu Apr 05, 2007 5:57 am
by jo2jo
good point on mesh.

I really wanted to use r52s, I was hoping the 15 and 19db antennas would ofset low power.. r52 does have good Rx sens btw.... I could use some extra nmp8602s that I have..but those are not very reliable.

so I guess thw question at thispoint is does anyone have any short range 5ghz on cm9 or r52 with slight obstructions experience?

thanks for the quick reply chipi.

Posted: Thu Apr 05, 2007 6:09 pm
by nickb
The Pacific wireless GD58-22 is a nice high gain grid in a very small package, if you need a few more DB. It's not much larger (if any) than the PA-19.

Re: 5ghz question, trees

Posted: Mon Jun 23, 2008 7:46 pm
by mmontz
We did a PTP test for a customer between 2 buildings @ 1.9 miles with SR9 on RB532 w/ 12db plat panels on each end. We had multiple trees and a hill to go through were still able to get a 1 meg link at -85db. This was with the standard b setting not 5 mhz but I would think with 1 tree a 1 kilometer you should be able to get 3 meg no issue. Make sure you use a higher cpu board like the 433AH so you don't have to deal with and CPU load issue.

Re: 5ghz question, trees

Posted: Tue Jun 24, 2008 6:40 pm
by 0ldman
I used a 24dBi Rootenna and R52's for a p2p shot. Still haven't put it up, but in testing, signal was awesome. -30's from 50ft away, shooting through 2 walls, my fridge, my washer/dryer/water heater/tv/etc.

It would have to be one hell of a tree to really put you down, although from time to time the ping might fluctuate.

Re: 5ghz question, trees

Posted: Thu Jun 26, 2008 9:13 pm
by ItsMe
I have a few 5GHz links with EMP-8602+S cards and PAC Wireless echo series 17dbi antennas. The links are all 1/4 to 1/2 mile and I could not get a reliable connection until I moved the antennas away from the trees.

Edit: It could depend a lot on the power, type of antennas used and the type of trees, (size of the leaves).

Re: 5ghz question, trees

Posted: Fri Jun 27, 2008 3:12 pm
by steveloomis
I have quite a bit of experience with 5 gig and as stated above, trees will kill it fast. Tree growth is a real problem too. A new link was installed a couple of months ago with -62dbm signal level and good performance over a 2 mile path. After a 3 week period the signal went down to high 70's then a week later middle 80's and would drop out all the time. Raised antenna a few feet and now -57dbm. Only thing in the way was a few scrub trees.

Very short distances, of under a couple hundred feet you can probably punch thru.

I hope this helps.

Re: 5ghz question, trees

Posted: Mon Jun 30, 2008 2:55 am
by CarulloS
The answer is almost always (unless its obvious based on other experience) that you never really know until you try because every environment is different.

I will agree with those above and say that do not ever build a new link knowing you have to go through trees unless it is less than a half mile and its like maybe one tree.

Scott

Re: 5ghz question, trees

Posted: Mon Jun 30, 2008 9:40 pm
by jorj
Try it. Most probably it will work.
You might still get into trouble when raining....... that tree will look like a reinforced concrete wall then....... because of the water.
I have perfectly working links with 1 oak, about 15m circumference, on about 1.5 km, with 12db omni+11 db yagi. No los at all, or maximum 1% on heavy rain. Your conditions may vary.

Re: 5ghz question, trees

Posted: Tue Jul 01, 2008 9:51 am
by Tanker
We have a redundant link - 4 Km (± 2½ miles) in 5.8GHz and we used CM9's with 27dBi grid antennas.

Generally we get -60 out of this link and we cannot actually see the other side through the tops of the trees. This link runs at 54Mbps air-rate all day and has been in operation for > 2 years. We also have it running in Nstreame.

So I guess to answer your question - yes it works, but I would approach it with caution.
Some testing might be the order of the day just to make sure it'll be stable.

Hope this helps.

Tanker