I think Daniel and I are saying the same things.
-----Original Message-----
From: Daniel White
Sent: Friday, October 30, 2015 10:13 AM
To: af@afmug.com
Subject: Re: [AFMUG] Dish polarity question
This comes up all the time with many manufacturers.
Almost all licensed microwave antennas a WISP is going to come in contact
with have circular feedhorns, meaning their polarity is determined by the
interface on the feedhorn. Typically, they are rectangular and single
polarity.
Then an OMT is added... depending on the radio it may be an external or
internal device. This combines the transmitters into a circular feed.
No voodoo required. The OMT makes a single polarity dish dual polarity.
Thank you,
Daniel White
afmu...@gmail.com
Cell: +1 (303) 746-3590
Skype: danieldwhite
Social: LinkedIn: Twitter
-----Original Message-----
From: Af [mailto:af-boun...@afmug.com] On Behalf Of Craig Baird
Sent: Friday, October 30, 2015 10:07 AM
To: af@afmug.com
Subject: [AFMUG] Dish polarity question
We are getting ready to put up a licensed 11 GHz 2+0 link using Cambium
PTP820S radios. We have two 11 GHz frequencies that are oppositely
polarized for use on this path. I had assumed that we would need to use
dual polarity dishes in order to make this work, but Cambium and our
vendor
are saying that we need to use single-pol dishes. This completely baffles
me.
How can a single-pol antenna transmit in two polarities? Cambium's answer
is that it's because we're using an OMT, and that device essentially makes
the
single-pol antenna circularly polarized, so it will transmit both
polarities. My
first thought is "what kind of voodoo is this?" Will this really work???
I'd sure
hate to start transmitting, only to find out from an existing license
holder that
we're interfering with them because one
of our frequencies is coming out the antenna in the wrong polarity.
Can someone confirm for me that this will really fly?
Thanks!
Craig
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