10 GHz polarisation

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Which polarisation should one use on 10 GHz EME

This is my personal view and you are off course free to decide different


 In the early years of 10 GHz EME stations used mostly linear polarisation, stations in Europe using vertical and stations in US using horizontal.

During an EME conference it was decided that in future the polarisation on 10 GHz should be circular,
since that time the discussion on 10 GHz polarisation has continued.
There are pro's and contra's in switching to circular polarisation on 10 GHz

Advantages as always thought were:
 no problem in spatial loss and two port output at feedpoint is a profit in using transmit receive changeover needing less isolation from a transmit receive relay
The building of a good circular feed system is more complex then building a Linear Polarisation feed

Some amateurs decided to follow up the advice to go to CP
Others decided to stay in LP
This situation lasted for more than 10 years

Then we had a more deep investigation into the use of CP against LP by Charlie G3WDG with important conclusions

•CP to CP performs worse than LP to LP by approx. 1.6dB
•CP to LP has 2dB loss
•No observed difference in spectral width between CP and LP
•CP is of course useful to overcome spatial loss in some cases
•For ultimate performance LP to LP with allowance for spatial offset is best

Since then the question about which polarisation to use still has not changed

In my opinion the way forward is that the recommendation in using CP should be withdrawn
and that use of LP on 10 GHz EME and higher frequencies is recommended.
In addition to that it could be recommended to use a polarisation rotor to correct for spatial losses.