Fade test will tell for certain if there's an issue between the two paths - you do not have to wait for degradation to do this. And, since you control both of them it should be fairly easy to turn one down while monitoring the other, etc. Fade tests should be done on every newly installed link and it’s a good idea to do this periodically as well.
From the Aviat Eclipse manual in the Commissioning and Troubleshooting Section: Fade Margin Test This test is designed to check that the expected (calculated) fade margin for a link matches actual performance. The expected fade margin should be included in the link installation datapack together with Tx power, system losses, antenna gains, the effective radiated power, free space path loss, expected receive signal level and the calculation for link availability. The fade margin test measures the difference in receive signal level between the normal, operational level, and the threshold level, the level at which bit errors appear. The threshold level can be specified for a bit error rate (BER) of 10-6 or 10-3. For Eclipse, the difference between 10-3 and 10-6 thresholds is not more than 2dB. CAUTION:Fade margin measurement should only be conducted after it has been verified that expected RSLs, as indicated in Portal performance screens, are correct at both ends of the link. If an RSL is low, the reason for this must first be investigated and resolved. When coupled with an ability to measure receive signal level at the receiver input, this procedure also provides an indication of receiver threshold, which can be checked against receiver specifications. For Eclipse, a fade margin test involves reducing the Tx power at one end of the link, and checking the error performance at the other using the G.826 data presented in the Portal Performance Screen. However, achieving a threshold RSL is only possible where there is sufficient adjustment available in Tx power. Tx power adjustment ranges apply down from the maximum power setting supported by the frequency and bandwidth option configured for the link. Therefore, in situations where the expected fade margin is greater than the Tx powerreduction range available within Portal, it is not possible to reach threshold. Nevertheless, reducing Tx power to its minimum and confirming error-free operation should still provide an acceptable degree of confidence. -----Original Message----- From: Af [mailto:af-boun...@afmug.com] On Behalf Of Mike Black Sent: Thursday, January 15, 2015 4:17 PM To: af@afmug.com Subject: Re: [AFMUG] Licensed backhaul pricing - still ridiculous Well, looking at your image you have some things that might be working against you: -The shadow of the antennas show they are both mounted in close vertical proximity which isn't ideal. -It appears there is an A/C enclosure near the south-facing dish, and it might provide a reflective face for scattering a signal back to the north-facing dish. -The building to the north looks taller than the one you are on, so this may provide yet another reflection path. Also, the license shows both paths are operating on vertical polarization, so this isn't helping either. None of this can be reliably modeled with available tools, and the antenna specs aren't necessarily reliable over these very short interference path lengths. The links may appear to be operating normally but in fact have a degraded threshold due to the bucking. This degraded threshold would then make the link more susceptible to interference from other licensed systems that were actually coordinated properly. As I mentioned, when the path in question starts to degrade you could try shutting down the other link to see if the situation improves. If it does, you may need to look into reconfiguring the site to avoid the interference path. For example, mount your dishes on either side of the A/C enclosure so you have the enclosure as a shield between the antennas. Hope this helps, Mike Black Black & Associates 727-773-9016 www.bamicrowave.com<http://www.bamicrowave.com> -----Original Message----- From: Af [mailto:af-boun...@afmug.com] On Behalf Of Seth Mattinen Sent: Thursday, January 15, 2015 3:32 PM To: af@afmug.com<mailto:af@afmug.com> Subject: Re: [AFMUG] Licensed backhaul pricing - still ridiculous On 1/15/15 12:08, Mike Black wrote: > If you look at the "TMCC MEADOWOOD" (WPOQ622) end of that link you will see > that there is a potential bucking situation between two of the college's > Dragonwave systems: Meadowood/Redfield is TX low while Meadowood/Red > Mountain is TX high, with only 100MHz separation. Have they tried shutting > one of these two paths down to see if the issue resolves? The path of redfield-meadowood-red are almost as close to a straight line as you can get without it being intentional. The two opposing antennas on the middle site are back to back. There should be enough front to back isolation on the Radiowaves 3' HP so it's not a problem, correct? Picture attached. ~Seth
