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Established Member
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AF-5X Poor Capactiy on One End

I have a 12.5 mile with with perfect LOS.  Im using AF-5X radios with 2' dishes and iso rings.  On one end of the link I have very low capacity no matter what channel I use.  What could be causing this issue?

af-5x link.png
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Re: AF-5X Poor Capactiy on One End

In that frequency range I would suppose interference, however you are also missing 5-6db of signal. You should be able to hit 8x if everything is well aligned and interference is minimal.

 

You can split the freqs and choose a different one for the weak side. Just run airview on both ends and pick the best channel. It's hard to find 50Mhz that is clean in most of the places we install these. I don't think we have any installed at 50MHz. We have a few with 40Mhz channels, but 30Mhz and 20Mhz are way more common on ours.

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Re: AF-5X Poor Capactiy on One End

These two sites are in the middle of nowhere with no interference.  Airview is very clean.  I've tried multiple frequencies from 5150 - 5840 and every one has similar results.

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Re: AF-5X Poor Capactiy on One End

Have you tried swapping radios and/or dishes?

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Re: AF-5X Poor Capactiy on One End

I have not tried that but was thinking about changing the radio.  Which end would you think would be the one causing issues?

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Re: AF-5X Poor Capactiy on One End

[ Edited ]

Depending on the mounting location, swapping hardware can often provide a quick sanity check before you dive deeper.

 

Real-world antenna gain is probably closer to 28 dBi on those (per Claude's AF-5X link calc -- we still lack proper documentation of gain versus frequency on UBNT antennas).

 

 

You should be able to hold 6X there with 8 dB of fade margin, with 8X on good days.

 

Several possibilities there, starting with alignment.  The AF-5G30-S45 dishes have fairly prominent sidelobes around ± 10° but they're down ~13 dBi from the main lobe so I doubt you're on one of those.

 

Any chance you have Fresnel zone issues at one end of the link?

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Re: AF-5X Poor Capactiy on One End

There are no fresnel zone obstructions here.   The link is wide open.

 

I agree that I should be seeing 6-8x in both directions on this link even with the current alignment.  Im not sure what is going on.

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Re: AF-5X Poor Capactiy on One End

You sure those jumpers are tight? We had a link that was baffling us and one of our guys was so mad he kicked the non pen or hit or something, and one of the jumpers fell loose. That's when he realized no one had double checked all the jumpers. I was quite surprised we had a link at all with it being just pressed on and not really screwed down.

I ask them a lot now if they double checked the jumpers. They love it. :-)
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Re: AF-5X Poor Capactiy on One End

[ Edited ]

Do you have short cp or enhanced mimo turned on?

 

Chuck

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Re: AF-5X Poor Capactiy on One End

Short cp and enhanced mimo is turned off on both ends.
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Re: AF-5X Poor Capactiy on One End

Any ideas?
Highlighted
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Re: AF-5X Poor Capactiy on One End

Hi,

 

Ideas...

 

1. Aiming? Where is that 5dB going? Are we aimed at a reflection?

2. You say clean spectrum - are there no other 5GHz transmitters near the rate low receiver? Are there other AF5X's there? Power (even off frequency) can desense the radio.

 

Chuck

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Re: AF-5X Poor Capactiy on One End

There's another AF-5x link at this site on a 40 mhz channel on 5230 facing the opposite direction.  GPS Sync is on.  Both are the same gender at this site.  The techs are working on tweaking the aiming now.  The problem I see is that even with the current aiming shouldn't the one side be more than 2x?

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Re: AF-5X Poor Capactiy on One End

My approach is to fix what is known and then, if there is any unknown left, look at that. Are both co-located units masters with GPS sync on AND with strict timing/NxN on? Can you turn the other link's radio off for a few moments and see if that improves things?

 

I believe you are receiving either noise from another source or multipath that is causing the issue.

 

Chuck

 

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Re: AF-5X Poor Capactiy on One End

I do not have strict timing/NxN on.  What does that do exactly?  What is the affect on capacity?

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Re: AF-5X Poor Capactiy on One End

[ Edited ]

Hi,

 

It potentially removes 1 symbol if one straddles the rx/tx crossover point for a given duty cycle. If you have co-located masters, it ensures that one isn't transmitting at the beginning of the other's receive window. This could be important if the links are not both of the same length or you are using different bandwidths.

 

I think it could cost you a few hundred kilobits per second, but, you will more than make that up if it increases your modulation rates.

 

Chuck

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Re: AF-5X Poor Capactiy on One End

I get the same results with strict timing enabled.

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Re: AF-5X Poor Capactiy on One End

Here's the link.  Where could I be getting multipath from?

2017-09-14 17_36_08-airLink - PTP.png
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Re: AF-5X Poor Capactiy on One End

FWIW, that airLink image shows 3 foot dishes.

 

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Re: AF-5X Poor Capactiy on One End

So you have sync enabled and strict timing / NxN on both of the colocated links? I am not sure what is happening yet...

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