> There appears to be several flavors of RG-6, the heaviest and most
> cost is one claiming extra shielding. (quad shielding?) The price
> looks ok even for the extra shielding at 60$/500 ft.
> My understanding is better shielding is less likely to effect the
> beverage pattern.
Hi Bob,
The shield is the least of things affecting coax radiation problems
on HF through upper VHF. Thick multiple-shields can be a good
thing because they can take a lightning hit with less worry about
opening up the cable shield, but forget about signal ingress
problems from poor shielding unless the cable is incredibly poor.
The general rule of thumb is if you strip the cable back and can't
see the cable's internal dielectric looking through the shield, it is a
good enough shield!
Most concerns in cable selection are related to mechanical and life
worries. Flooded cables should be used for all underground wiring,
wiring that lays in wet areas, or wiring that rodents and animals
might chew. Other than than problem and loss concerns, one cable
is about as good as another.
The biggest problem by far with interaction and signal ingress are
common mode currents, and that depends on connections at the
ends of the cable and how the feedpoint is arranged.
Do not route the cable parallel to the antenna and close to the
antenna. Use an isolation-type matching transformer at the
antenna. Don't worry about Faraday shields and other things in the
transformer, they are for the most part useless. Just use a straight
primary/secondary-type transformer using the correct core material
(73 material works about best in this application).
You can ground the cable to a separate ground rod several feet
from the antenna (I usually don't bother, since my cables are all
buried), but never ground it to the same ground as the Beverage
feedpoint.
73, Tom W8JI
W8JI@contesting.com
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