[Moon-net] 10GHz Polarisation

[Luis Cupido]

Brian,
and all,

I just processed some signals from the Bochum's experiment
being Amsat DL transmitting linear and G4NNS receiving
linear rotating from 0 to 90 degrees. The graphic (that I hope
Brian post on his web pages soon) clearly shows the amount of
polarization preservation at that experiment.

The signal is 20dB above noise when aligned and 10dB above noise
when orthogonal.
This is even more polarity conservative than the experiment
with RX at OK1KIR that I processed and presented in my Dubus
article, where 6dB were observed.

### This clearly show that we are not in a marginal situation ###
If we believe in the results of the tests conducted so far,
In a QSO between two average size stations with a few dB of S/N at each
end, 45deg misalignment means NO QSO.

> At present my view is that for inter EU or EU - US contacts following the
> convention of EU vertical and US horizontal the benefits of circular will 
> be
> marginal at best.

Brian, this is a recurrent issue. There are stations with polar mount and
modified rotational mounts that don't maintain linear polarity alignment
while tracking. (those to maintain the convention must have variable linear 
!!!)
Not to mention spatial offset, for example I'm 45 deg off Russia and
90 + 45 off Japan... well we no longer have just central Europe
and central US on the game.


> If the circular system has more than about 1dB of
> elipticity

Why should it have more than that ???


> or if the circular polarizer system involves coax,

Why should it involve coax ???
(only if we want, for example the PwrAmp out is SMA
and we need an sma cable to connect to the feed)
(otherwise all is waveguide...)

> particularly
> on the receive side,

Geeee........ why are you devoting time to such pessimistic
and bad suggestions ???

> that marginal advantage could be negated.

Why are you saying it is marginal when the first batch of tests
shown something like 6dB
And the last ones with the signal received at your OWN end
show 10dB !!!!!!

---

Folks, the results I've processed with signals from various
stations ALL point in the same direction.
There are depolarization that varies from 5 to 10dB down.
Never had a SINGLE example of total depolarization by anyone ;-)

>From all this, it is pretty obvious now that

### if there is room for polarization misalignment in linear###
### they would better in circular ###

or, if we don't want to allow room for misalignment,

### if we say that EU-EU and EU-US are okay
with the old standard of vertical / horizontal ###
### we are forcing polarmounts and alike plus
some geographical regions to use rotable linear ###

It is as simple as that, in my humble opinion.

---

Folks,

I'm starting to believe that this discussion may
easily leave technical grounds and enter emotional
fields (and it will not be the first time that something like that
happens on moon-net ) and that is exactly where I start to
lose interest ;-)

(or start writing poems, and you don't want that to happen  ;-)

Luis Cupido.
CT1DMK.




----- Original Message ----- 
From: "Brian Coleman" <brian-coleman at tiscali.co.uk>
To: "Moon Net" <moon-net at list-serv.davidv.net>
Sent: Friday, September 29, 2006 9:21 PM
Subject: [Moon-net] 10GHz Polarisation


> Hello All
>
> Anyone interested in the 10GHz polarisation discussion  may be aware that
> with others various tests are being conducted to try and establish whether
> circular polarisation will be advantageous at 10GHz or not. Some results 
> are
> posted on my web pages at http://myweb.tiscali.co.uk/g4nns/Poltests1.html 
> .
> In my view, there are further tests to be done before a balanced 
> conclusion
> can be reached.
>
> At present my view is that for inter EU or EU - US contacts following the
> convention of EU vertical and US horizontal the benefits of circular will 
> be
> marginal at best. If the circular system has more than about 1dB of
> elipticity or if the circular polarizer system involves coax, particularly
> on the receive side, that marginal advantage could be negated. Where both
> these are true I doubt there will be any useful advantage.
>
> If anyone wants to continue this discussion and analysis AFTER the other
> necessary tests have been done I would be pleased to hear from them. The
> tests which are needed include:- Circular to Circular and Circular to
> rotateable linear (perhaps concurrently with the cp-cp test). When that 
> data
> is available a balanced discussion will be possible.
>
> My thanks to the AMSAT DL team at Bochum,  the OK1KIR team and the IQ4DF
> team for their help with the tests done so far.
>
> If anyone is put off from coming on to 10GHz EME because they feel they 
> must
> have the additional complexity of a circularly polarised system that would
> be a pity.
>
>
>
> 73 Brian G4NNS
> Currently 9W, 3.7M, remote controlled linear polarisation, 24 initials on
> 10GHz.
> I have a choice of circular or linear on 3.4 and 5.7GHz but so far all 
> QSOs
> have been with linear.
> PS anyone for circular on 24GHz.....
>
>
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