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 <mailto:[email protected]>
*Sent:*Friday, October 23, 2015 12:35 PM
*To:*[email protected] <mailto:[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] <mailto:[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] <mailto:[email protected]>– 314-735-0270
x103 – www.linktechs.net <http://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] <mailto:[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.
