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900 mhz vs trees

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900 mhz vs trees

We have an  important node at our Red cross Hq. Until recently it has been able to connect to another of our key nodes without problem.
However this summer we get only a weak, unusable signal. We have replaced the antenna with a different node, tried a different cable and POE, all of which
made no difference.  So we are attributing the signal loss to the growth of big trees in the signal path.  The other node is only 1 mile away.
The other node has a Rocket M2 with a 13 dBi omni H/V antenna, 180 feet high.  Red Cross now has a Mikroitk LHG XL2,  21 dBi node, 50 feet high.

One possible solution is to use 900 MHz.  But we would have to buy lots of expensive equipment and antennas and tower climber just to find out
if it would work. And the list of supported equipment lists the preferred Rocket M9 as being supported only for XM, and the ones likely available are
XW now.

Comments and suggestions please?


w6bi's picture

If the omni antenna is the Ubiquiti AMO-2G13, it has 2 degrees of electrical downtilt.    Assuming the Red Cross and the other node are at the same ground level elevation, the up angle at the other end (the LHG2) should be 1.97 degrees.  Assuming it does have the prerequisite 2 degrees of elevation, they are perfectly aimed (elevation-wise, anyway).   

Your Mikrotik LHG XL 2 has a power output of 25 dBm (max) and a gain of 21dBi
A Rocket M2 has a power output of 28 dBM (max) and a Rocket dish for 2 GHz would be 24 dBi gain.

Swapping the LHG XL2 out for the Rocket dish and Rocket M2 would theoretically give you 6 dB more link margin.  But the trees keep growing...   You'd have to decide if that's worth the effort and expense or not.  (on the other hand, it's probably more accessible than the  Rocket + omni at 180 feet...)

Hope that helps

Orv W6BI

More gain, please.

I had a link with identical parameters as yours, 1.0 mile, a few trees, but with two 2 23dBi MIMO panels on 5Ghz. There was occasional latency with weather as the MSC rates shifted, but the link worked quite well and never went down. The key with trees is punching through them with a highly directional signal, and some luck! 5Ghz will give you a little more gain+power. If it's a whole forest of pine trees then you might stick with 2.4Ghz but as you know there is really only 1 good channel to work with.

I also had antennas at the same two locations with the same trees, same path, as a test. One was a 13dBi MIMO omni and one panel on 5Ghz. It would never link up... Just not enough signal coming back from the omni even though it could hear the panel.

900MHz is a noise-fest anywhere I've ever tried it and equipment is hard to come by anymore. I wouldn't bother unless you're in a quiet place in the middle of nowhere.


wa2ise's picture
I live in a tree infested

I live in a tree infested area, and I'm lucky if my signal can connect to anything beyond 1/3 of a mile...900MHz or 2.4GHz

W2TTT's picture
I live in a tree infested

Why don't you try a 5 GHz link with W2JC using the Mikrotik dish transceivers? $80 for each end.  See above posts for specific models.


Thanks for the suggestion.  Unfortunately I did not explain the entire situation.  The tall tower at the other end serves a wide area, so we could not
do anything to change that. The tower is owned by the county, and they have to approve any changes we make, and we are required to hire a licensed
tower climber, which adds $500 to the equipment cost of any  change.  And then we could not be sure it would actually work.  We can change
most anything we wish at the Red Cross end.  It seems to be a hopeless situation at present.


nc8q's picture
Rocket M2 with a 13 dBi omni H/V antenna, 180 feet high

Hi, Bob:

 I would like to compare the /mesh page of your
2397 MHz Omni at 180 feet with our
2397 MHz Omni at 175 feet.
Please share your mesh page.


Image Attachments: 
I will send this as soon as I

I will send this as soon as I can.  Right now there are local equipment problems holding me back.


nc8q's picture
Rocket M2 with a 13 dBi omni H/V antenna, 180 feet high

Hi, Bob:

 Are there other nodes that link with the Rocket M2 with a 13 dBi omni H/V antenna, 180 feet high?
Did they also suffer similar signal loss?
If the other linked neighbors were dual stream, was the attenuation in both streams or only one?
We had a Rocket M2 with omni H/V antenna at 220' elevation that only worked in one polarity.
We assumed it was the vertical polarity that was working.
This node is 'dead' now and still at 220' a.g.l. :-|


Trees etc

Chuck - I have a copy of the mesh status, but it is in html and I can't figure out howBob W8ERD to get it into a form that this mail will accept.
The other nodes do not have this problem as they arr higher than the trees. All are dual stream.


nc8q's picture
Trees .vs. Omni antennas at 175+ feet elevation.

Hi, Bob:

 Here is a way around the attachment limitations:

Add ".tgz" to the end of the filename and add as a file.

Address an email to me at arrl dot net with the file attached.
Once I receive your file I will delete this forum message number
so not to  leave instructions on how to defeat the forum limitation.



mesh ve trees

Thanks Chuck.  I tried that but the gmail mailer refuses to send it, claiming it is a security threat.


nc8q's picture

Hi, Bob:

 I sent you an email to your address shown at from my active ham radio email address.


@wa2ise.  I know the tree

@wa2ise.  I know the tree problem all to well here in Wisconsin.  I have been a proponent of 802.11/mesh for years but sadly have never made much head way because of where I live; the topography, trees and access to towers and tall buildings are issues.

Outside of the traditional 802.11 arena these options might be of interest:

Beyond Line-of-Sight UHF Digital Communications with the LoRa Spread Spectrum Waveform - KG5VBY (Youtube DCC Video)

Hamnet over 70cm : NPR (New Packet Radio) - IP over 430MHz Ham Radio, up to 500kbps, 20W RF by F4HDK

Other options include: 

CalAmp Viper SC+

4RF Aprisa SR+

Icom ID-1

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