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Re: Polarisation On L- Band



At 08:04 PM 5/19/03 +0200, Barry Murrell ZR6DXB wrote:
>Hi All
>
>A dumb question - I am currently getting set up for L-Band uplink, and have
>an M2 35el yagi waiting to go up. Should I use horizontal or vertical
>polarisation, and are there any specifics to note when mounting the antenna.
>I got the antenna second-hand, and the mounting bracket is missing. I need
>to make up the relevant mount, so any info or comment would be appreciated!
>
>73
>Barry ZR6DXB
>Johannesburg, South Africa

Barry,

Always happy to see more countries getting on AO-40 and I'm sure there not
many from S. Africa.  UNfortunately the orbit of AO-40 is not likely to
ever provide us a common view.  Western Europe is a challenge for us
Alaskans (never above 2-4 degrees from the horizon).

But to your question, the 1268-69 MHz antenna on AO-40 is circular polarity
so it will not matter which orientation you choose.  I had a loop-yagi
setup for mode-L and found it convenient to mount in the vertical-pol
position (no interaction with my metal crossboom).  One factor that you may
want to consider is if there is any local 1296 activity.  If there is then
chose whatever polarization is in use so you can use the antenns for local
operation on 1296 (assuming the M2 works at 1296, too).

A strange situation exists in Alaska in that all terrestrial ssb/cw use on
2m and higher* is vertical polarity which is counter to use in the lower 48
states where Horinzotal is standard.  This has occured up here becuase most
hams have migrated from VHF FM operation and want to use existing
"repeater" antennas.

73, Ed - AL7EB
*Note:  since there is no microwave activity established yet in Alaska, I
am promoting Horzontal as the default polarity >2300 MHz up here.
50-144-432-1296-2400-3456-10,368-24,192 MHz
BP40iq

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