Reid wrote:
>
>Greetings:
>
>Is there a recommended (i.e., possible) method for using 9913 (non-flex)
>coax in a rotating antenna application? I have a set of m^2
>uhf/vhf yagis mounted on one boom with feedpoint near the ends (both
>yagis have 10 foot booms). The cross boom to which the pair is mounted
>is 7 feet long. Given that I need 360 degrees az and 90 degrees el, can
>9913 be used without breaking? If so, what would be the recommended
>method for connecting the coax?
If you're going to use this cable, you have to treat it as "consumable",
and expect it to fail after a certain total amount of flexing... but
that could be a long time, depending on your operating habits.
For what it's worth, I have been using a European 9913 near-equivalent
for about 5 years now on the 432MHz EME system (can't use RG-213 because
it melts, and Andrew Superflex broke apart very quickly). The system has
360deg azimuth and 70deg elevation, both of which rotate very slowly to
track the moon, but also 360deg polarization rotation which is used a
lot when operating. It's still going OK, mainly because EME sessions are
maybe only one weekend a month, but I'm conscious of gradually using up
the fatigue life of the inner conductor.
Another part of the answer is to make certain there are no stress
concentrations. In other words, the flexing must be evenly distributed
along the whole length. Also, the ends of the cable must be firmly taped
down so there is absolutely no stress on the connectors.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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