09-13-2017 04:02 PM
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?
09-13-2017 05:31 PM
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.
09-13-2017 05:45 PM
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.
09-13-2017 06:54 PM - edited 09-13-2017 07:12 PM
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?
09-13-2017 06:57 PM
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.
09-13-2017 07:31 PM
I ask them a lot now if they double checked the jumpers. They love it. :-)
09-14-2017 10:51 AM
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.
09-14-2017 11:03 AM
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?
09-14-2017 11:22 AM
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.
09-14-2017 11:49 AM - edited 09-14-2017 11:49 AM
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.