[amsat-bb] CP Antenna questions
ko6th.greg at gmail.com
Sun Sep 23 16:18:11 PDT 2012
I've just obtained a nice, old, but disassembled, KLM 144-150-16C 2m
circular antenna. I think I have all the pieces (yea!). That, plus a tree
trimmer, and I should be in great shape for an upgrade. The old antenna is
a linear (vertical) 8 element beam of unknown pedigree. It's been working
fine, but I couldn't pass this one up.
1. The antenna does not have a polarity switch. The instructions are for
RHCP ("as used by Oscar-7" to give you an idea of it's age!). Given that I
don't (yet) have a polarity switcher, is that still the best polarization?
2. I have a 2m preamp that I have mounted some 10' away from my current
antenna, on the mast; I'd like to put it closer. Is it ok to mount the
preamp on the antenna itself, between the elements? I'm guessing not. How
about on the cross-arm, a couple of feet from the antenna boom?
3. The instructions recommend routing the cable out the back of the beam,
and looping it over to the support mast. But that won't work well as it's
rotated in elevation (it will get caught on the stuff below). My plan is
to run the cable forward and then sideways out at the mount point in the
middle. Will this have a significant effect on the polarization? The
cross-arm is a wood closet pole, not metal, but I'm thinking that the
antenna should be mounted in the X orientation instead of +, to lessen the
effect of the cable shield on the pattern. Good idea, or not?
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