Or in addition to low signal, maybe the signal quality is crap. This can happen if your signal is getting ducted or a lot of the signal is coming from reflections. It would be interesting to see a graph of modulation level, I wonder if this link is ever getting to full modulation.
From: Adam Moffett Sent: Friday, October 23, 2015 2:01 PM To: [email protected] Subject: Re: [AFMUG] 20+db swing Maybe there's a cliff....from -65 to suddenly nothing On 10/23/2015 2:53 PM, Scott Vander Dussen wrote: Ken- Thanks, all good observations and questions that I’ll need to dig into. I know for certain we have HAAM (Hitless automatic adaptive modulation) enabled, not sure why it’s dropping around -65, that’s more weirdness. `S From: Af [mailto:[email protected]] On Behalf Of Ken Hohhof Sent: Friday, October 23, 2015 10:56 To: [email protected] Subject: Re: [AFMUG] 20+db swing Yeah, that’s what it looks like. I would also worry that you only seem to be getting into the 40’s around sunrise and your steady readings are around –56. Do calculations and past experience say you should be that low? What I’m thinking is that if you tried to align it during a fade, you may have misaligned the elevation. I would only do alignment when the signal is stable. It is possible to get a reflection off a wide area of flat ground or a thermal layer at dusk/dawn that is stronger than the main path, and to align on the reflection. Another question is why the link is dropping at around –60? I would expect a licensed link to stay up as low as –80, unless you have it set for fixed modulation. Do you have ACM on this link? From: Scott Vander Dussen Sent: Friday, October 23, 2015 12:35 PM To: [email protected] Subject: Re: [AFMUG] 20+db swing Yes, “thermal inversion layer” or whatever- I wasn’t involved in the call to SAF, but I believe this is why they wanted us to lower the tall side to avoid “reflecting” off the thermal differences. The signal swing is a bit rhythmic From: Af [mailto:[email protected]] On Behalf Of Keefe John Sent: Friday, October 23, 2015 10:31 To: [email protected] Subject: Re: [AFMUG] 20+db swing signal can change from thermal ducting On 10/23/2015 11:40 AM, Dennis Burgess wrote: Signal don’t change unless you have rain, etc. The last two things are wind (antenna alignment) and tx power. That’s it.. Dennis Burgess, CTO, Link Technologies, Inc. [email protected] – 314-735-0270 x103 – www.linktechs.net From: Af [mailto:[email protected]] On Behalf Of Scott Vander Dussen Sent: Friday, October 23, 2015 11:31 AM To: [email protected] Subject: [AFMUG] 20+db swing 17 mile link, 11GHz, 3’ dishes- it’s worked fine for years and over the past few months there has been an increasing fluctuation with signal quality. SAF support suggested we were too high on one side and actually lowering it would help, it didn’t change. We’ve verified LOS, even switched out to a DragonWave 11ghz pair of radios and it exhibited the same behavior as the SAF. We then moved one side of the link to a different tower about 6 miles away (still makes overall link 17 miles) and we’re getting the exact same behavior. In years’ past the signal was consistent, now we’re seeing this: Am I missing something? Same behavior with two different radios, frequencies, and towers. There are no environmental conditions like moisture, etc. that are obvious culprits.
