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Re: 435 MHz CP antenna



First Tracy K7KCS asked:

I would like recommendations on an uplink 70cm CIRCULAR polarized antenna
for AO-40 (or linear if I don't need circular . . you tell me).   My
available power is about 30 watts.  I'd prefer to purchase not build.

Then Wayne replied (in part):

<snip>
You could also try to find a used KLM circular polarized antenna.  KLM is
out of business, but they made great antennas.  The most popular KLM 435
MHz antenna had 40 elements on a very long (19 foot?) boom, which is
inconveniently long in my opinion.

30 watts (with low cable loss) to a 436CP30 is probably barely enough power
to "meet LEILA" when the off-pointing angle is low.  Times Microwave
LMR-400 is a good low-loss cable for short-to-medium cable runs.  It has
about the same loss as Belden 9913, but it more water-resistant.

Now Jim - K6CCC adds:

KLM made two versions (for each of the two bands) of their CP yagis.  The
"long boom" version that Wayne refers to is 22 elements on an 18.5 foot
boom for 2M and 40 elements on about a 12 foot boom for 430.  These are the
antennas I use for satellite and have been very happy with the antennas,
but the CP phasing switches have been problematic, and I understand that is
a common problem.  One of these days I'll rebuild the phasing switching
with some better relays I recently picked up.  Here is a photo of these
antennas:
http://home.earthlink.net/~k6ccc/Photo/Pics/SatAnt1.html
There are some more antenna photos on the site, just click the link for
Amateur Radio Photos to see more.  BTW, that photo was taken before I put
up S-Band.  For a mode U/S station of course the 2M antennas are not
required, so a fairly small rotor won't have any trouble with the 430
antennas, however your 2.4GHz antenna may be a different story - depending
on what you have there.

I would agree with Wayne that 30W is barely enough.  30 at the antenna may
be OK, but you wont get that much to the antenna due to feedline.  You can
expect to be useable, but one of the weaker signals on the bird.  some of
the stations with less than ideal receive capability will have some
problems hearing you.

73
-----------------------
Jim Walls - K6CCC
k6ccc@amsat.org
Mobile Radio Operations
Southern California Edison Co.
Ofc:   626-302-8515   -   PAX   28-515
FAX:   626-302-7501   -   PAX   27-501


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