If you rotate the whole thing 90 degrees with respect to the antenna waveguide
you could get the radios on the wrong polarizations.
Or you are peaked on a side lobe.
Have you tried to swap radios on one end?
From: Mark Radabaugh
Sent: Friday, March 6, 2020 10:29 AM
To: AnimalFarm Microwave Users Group
Subject: Re: [AFMUG] PTP Microwave antenna question
Odd thing is I don’t see any way to assemble this any way that would swap
polarity. Only way to screw it up would be internal to the OMT itself. We
are doing XPIC with this link which we have not done in a lot of other places,
so that is different.
Mark
On Mar 6, 2020, at 12:22 PM, ch...@wbmfg.com wrote:
V&H being swapped will always cost you at least 20 dB and if you have them
precisely aligned V&H I can see where 40 dB is reasonable.
From: Ken Hohhof
Sent: Friday, March 6, 2020 10:18 AM
To: 'AnimalFarm Microwave Users Group'
Subject: Re: [AFMUG] PTP Microwave antenna question
OK, that says the antenna should be dual pol capable. So … is a puzzlement.
You’d expect a problem would cost a few dB, not 40 dB. Unless H & V were
swapped.
Sounds like Cambium is looking into it, maybe they come up with some ideas.
From: AF <af-boun...@af.afmug.com> On Behalf Of Mark Radabaugh
Sent: Friday, March 6, 2020 11:00 AM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Subject: Re: [AFMUG] PTP Microwave antenna question
It’s currently 2 single pol Horizons on a Dragonwave OMT mount that combines
the H&V to the round waveguide on the back of the antenna.
Mark Radabaugh
Amplex
22690 Pemberville Rd
Luckey, OH 43443
419-261-5996
On Mar 6, 2020, at 11:19 AM, Ken Hohhof <af...@kwisp.com> wrote:
We put 11 GHz 820C w/XPIC on existing Trango 3 ft dishes replacing single
pol ApexPlus ODUs and everything went as expected. I’d have to look up the
details but I think it worked because Trango used Remec circular even with
single pol except for 6 GHz. We should have adjusted for best XPIC
cancellation but instead we just made sure the ODUs were plumb. But I think
what we did was roughly the same as what you’re doing, so it should work.
We got a couple bad 820S radios last year, failed the RF loopback test, but
it sounds like you have pretty thoroughly verified it’s not bad radios.
Were the Dragonwaves single or dual pol?
From: AF <af-boun...@af.afmug.com> On Behalf Of Mark Radabaugh
Sent: Friday, March 6, 2020 9:37 AM
To: AnimalFarm Microwave Users Group <af@af.afmug.com>
Subject: [AFMUG] PTP Microwave antenna question
We have installed a lot of Cambium 820C radios without much trouble. Yes,
the configuration takes some getting used to but we probably have 46 links
working and installed, so it’s not like it’s our first rodeo configuring these
things.
And then we tried something new - reusing a 4’ Andrew Dragonwave antenna
in a XPIC configuration. We purchased the Cambium adapter plate that clips
onto the antenna radio mount and presents the 820C mount for the OMT. Take
off the dual Horizon radio OMT, add the 820C and the RF signal is shit - in the
-80’s from the mid 40’s. Reverse the process and put the Horizon’s back on
and the signal is fine.
So we thought we had a bad 820C. It’s happened before. So we take two
different sets of 820C’s and test them one at a time swapping them in for known
good installed radios on working links. The 820C’s are fine.
Okay… we forgot to test the OMT's when we did that. So we try the OMT’s
in the shop - and they work fine.
At this point the only thing left is the antennas themselves and the
adapter plate. The adapter plate is nothing more than a hole in a aluminum
bushing with a couple of small steps to match diameter between the OMT and the
antenna waveguide. Pretty hard to screw up.
We have a pair of Dragonwave antenna’s in the shop that we can mount all of
this to and try here - and we can’t get a decent signal even 20’ apart. I’m
at a loss at this point. The only part that doesn’t appear to work is the
adapter plate - and there is nothing interesting about it.
How the heck can this not work:
<image001.jpg>
<image002.jpg>
I can’t buy that the alignment of the antenna would need to be adjusted.
That makes no sense in my head. Am I wrong in that assumption?
Mark
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