[Moon-net] Polarity switching - 45 degree steps - Myth or Secret Weapon?

[Leif Asbrink]

Hi Vic,

I am not aware of anyone who made 45 degree switching on the
tx side. I know for sure that I lost several highly wanted 
QSOs because I did not have it....

On the receive side it is trivial.

Use two Rx/Tx relays and two preamps. Bring both cables down into
the shack. Adjust the noise floor to become equal, then tweak
the cable lengths so the received phase is the same. This is
easy in the X configuration, but difficult in the + configuration
where you have to wait for a high elevation EME signal to be equally
strong in both channels. Then tweak cable lengths so the signal 
dissappears when you add the two cables in a T-connector.
Insert a 180 degree phase shifter in one of the cables to 
allow the opposite polarization. The remaining polarisations
are obtained by switching off one or the other preamp.

This was my first X-pol system. It worked extremely well:-)

Once you have two pre-amps, maybe you should consider adding
another channel all the way to the loudspeaker. That way you get
full control of polarisation at AF. One way is to use one ear for 
each antenna. Another is to use Linrad for an optimum combination 
of the two.

73

Leif / SM5BSZ



> So far, no one has responded with any experiences. I am beginning to  
> wonder if 45 degree switching is a Myth or a secret EME weapon?  :-)
> 
> Has anyone had any good or bad experiences using 45 degree switching?
> 
> Thanks,   Vic - K4UCY
> 
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