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Cable Loss:
There
is a little-known fact that coaxial cables, such as RG-8, RG-213,
RG-214, and RG-58, have more RF loss in one direction than the other.
This is due to the
twist
direction
of the
inner conductor and the
braid
twist
on the
outside of the cable.
The inner
conductor controls forward power and the braid is the return path for
receive signals.
This
phenomenon was discovered and documented by Professor Loof Lirpa (SMØAFD)
at the University of Stockholm, Sweden, in 1956. Quality cable
manufacturers print a tiny arrow on the outer jacket of their cables
indicating which way the transmitted RF should go.
If the coaxial cable in your shack does not have an arrow, you can
experimentally determine it. Connect your transmitter to one end of a
cable and a wattmeter, with dummy load, to the other end. Check the
power and then reverse the cable to see which way it works best. Then,
mark the cable with an arrow so you will always know the “sending end”
of the cable for minimum loss to your antenna.
Install
it accordingly.
This can
be a significant advantage for an Amateur Radio
operator trying to make a long distance contact.
April Fools
Editor’s note: Mark Persons is
Certified by the Society of Broadcast Engineers as a Professional Broadcast
Engineer with over 30 years experience. He has written numerous articles for
many industry publications over the years. His website is:
http://www.mwpersons.com
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