Yeah, I was not thinking of a system with the same freq on both.
Odd. Perhaps a rectangular waveguid somewhere in the system or the wrong
freq waveguide somewhere.
The photos show what I would guess is 11 GHz. That is about .750" dia plus
or minus for most system. I think dragonwave used .777"
-----Original Message-----
From: Caleb Knauer
Sent: Friday, March 6, 2020 10:40 AM
To: AnimalFarm Microwave Users Group
Subject: Re: [AFMUG] PTP Microwave antenna question
With XPIC it wouldn't matter that slot 1 was talking to slot 2 on the
other side, it wouldn't know. At least I think anyways. Since it's
just looking for RX on the frequency it's set, and it's on the same on
both ends, and it'd still have XPD to separate the two. You could
rotate one end 90 degrees to simulate on the office rig to test I
suppose. Plus anyways if you can't get signal worth a flip on the
office rig, even if it was a polarity thing, that short of a link
should blast it through to something you'd see.
Only thing I can think of is that something in that tube is not
aligned, bad press fit or mill or something like that and the waves
are getting blown out of phase or similar. There's not but one way to
put it together, and 820c -> OMT takes it to circular and you have
circular to dish.
On Fri, Mar 6, 2020 at 12:30 PM Mark Radabaugh <m...@amplex.net> wrote:
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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