Okay. So, let me throw another wrinkle in the mix. I'm wanting to
use an 8-foot Radiowaves dish that we've had in storage for this shot.
Looking at the back of the feedhorn, there is a plate where the
flexible waveguide attaches. That plate has a rectangular hole in it.
However, I can see that underneath that rectangular hole the
waveguide is actually circular. So, could I use an OMT with such a
configuration? Would have have to replace that plate with one that
has a circular hole instead of a rectangular one?
Craig
Quoting Daniel White <afmu...@gmail.com>:
I agree... we are saying the same things... just in different ways :-)
Many vendors now are utilizing integrated OMT's... the Ceragon IP-20S uses
it for instance.
Long story short - don't worry if the BOM says Single Pol if it includes an
OMT.
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 ch...@wbmfg.com
Sent: Friday, October 30, 2015 10:41 AM
To: af@afmug.com
Subject: Re: [AFMUG] Dish polarity question
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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