----- Original Message ----- From: "Angus" angus@young5769.freeserve.co.uk To: amsat-bb@amsat.org Sent: Saturday, July 26, 2008 3:29 PM Subject: [amsat-bb] Re crossed yagi question.

OK now that I have a crossed yagi in the X format, I must say I am very

pleased with its performance.

Here is the question with the yagi in the X format, does it perform as

well when set with delay lines to horizontal polarity as a yagi with the same gain beam width etc set in the horizontal polarity?

I ask this as I don't have a lot of test equipment and most of my results

are a 'by ear' equipment.

I just wonder if anyone (someone will have I am sure) has done any

checking to see what if any difference there is between X set to Horizontal and a normal yagi set in horizontal?

Thanks for allowing me to ask what might be some very daft/odd questions

hi

regards Gus M0IKB

Hi Gus, M0IKB

If you want the switching polarization agility be happy with your crossed yagi in the X format. In theory your polarization switcher send 50% of power to the \ yagi and the other 50 % to the other / yagi. The components \ and / can be combined by the switcher to make a resultant that can be horizontal or vertical but any polarization switcher has losses due to relays and delay lines. In particular to divide exactly the power 50% to the \ dipole and / dipole is difficult and this can generate a resultant that is not exacly horizontal or exactly vertical. In conclusion if you feed 100% of your power to a single horizontal antenna or to a single vertical one it is better but if you need the polarization agility to get V-H-RHCP and LHCP there is no way to do different and a good polarization switcher is mandatory.

For the theory on how a four polarity switch works read please the article "Switching Four Polarizations on a 70 cm Crossed yagi" Part-1 publisched in the AMSAT Journal March/April 2007 www.amsat.org

For building the switcher read Part-2 in the issue May/June 2007

73" de

i8CVS Domenico