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Re: Circular polarization question



True RHC to LHC will be > 20 dB on a line of site terrestrial path.

RHC or LHC to Linear (Vert or Horiz) will be 3 dB loss.

All this changes when you are looking off axis, i.e., with SQUINT. At high
squint angles you will find that the polarity of design (Right Hand
Circular) may be exactly WRONG and Left Hand Circular will work better, but
only during periods of high squint.

Yes, the loss of RHC to LHC is the same as Horiz to Vertical on a line of
site terrestrial path. Theoretically it can be as much as 40 dB as I recall,
but practically it tends to run 20 to 30 dB.

Once you start scattering (tropo, etc) or involving the ionosphere, or
working on poor squint angles to the satellites, then all bets are off.

In general, I find using RHC up and Linear down with a good antenna and low
NF,  high gain downconveter,  works extremely well. (M2 CP30 and HyperLink
Tech 39" BBQ Horizontal > UEK 3000 d/c).

For my operating, I find those times when LHC is superior to the designed
RHC of the bird to not be of sufficient length to warrant the expense of
switching polarities. (split infinitives?!?), or the increased complexity
and lack of reliability associated with the switchboxes.

73

...hasan, N0AN


----- Original Message -----
From: "Randy Mclean" <rmclean@natdoor.com>
To: <amsat-bb@AMSAT.Org>
Sent: Thursday, June 06, 2002 9:47 AM
Subject: [amsat-bb] Circular polarization question


> Being that I am new to the Satellites and to AMSAT(new member as of Dayton
> 2002), I have a quick and maybe a dumb question. I just acquired the m2
> 2MCP14 and 436CP30 antennas. I see that there is an option that allows you
> to switch between LHCP and RHCP. How useful is it to have this ability.
> When I'm receiving a signal that is RHCP and I'm set for LHCP or vice
> versa, what amount of loss will I experience. Is it equal to the amount of
> loss experienced between Horizontal and Vertical polarization on the
linear
> setup? Thank you for any assistance.
>
> 73's de wo5m
>
>
>
> --
> Randy Mclean
> Security/Network Administrator
> rmclean@natdoor.com
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
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