Interesting answers...
I am wary of any solution that leaves transmission lines loose and
ungrounded. I have seen how lightning can arc from a disconnected cable
across a desk and zap a radio. It my friend's SWL installation, but I
doubt lightning cared what sort of radio it is toasting.
Thus, I am skeptical bout just opening a knife switch on the wall and
not grounding the wires in some way. I am even a little worried about
Joel's balanced arrestor acting alone on an unterminated (open) knife
switch. I would ALSO ground the two wires on a buss bar. (See Wireman
857 and 858 - which I use.)
I really like Stuart's notion of a double throw
knife switch that grounds both sides when off
the air.
Coax enters my shack via 8 inch bulk head connectors. I use a properly
rated and grounded arrestor outside, and all disconnected lines are
routed to a buss bar with extremely short RG-213 patch cables (using the
same push on connectors Joel mentioned.) My theory is I can disconnect
all my antennas and ground them directly, and separately, from the
radios. The support masts are also grounded - and all grounds are bonded
together - using four (4), 8-ft ground rods located about 4 to 6 feet
from each other, they are all about 6 feet from the shack coax entry point.
My remote coax switch is grounded to this set of grounds, as well. I
switch the system to the dummy load when I close the station. I
disconnect the radios and patch the inside bulk head connector to the
grounded buss bar - so any energy that gets past the outside arrestor
(connected to the four ground stakes) is routed to the grounded buss bar
and directed back outside, again to the four stakes. My only concern is
that I may have created a ground loop that causes me problems, but so
far, no problems.
As per above, I would never leave a disconnected wire or cable loose and
ungrounded (disconnected)-- all unused lines are routed directly to the
grounded buss bar with a very short, heavy patch cable. I use screw on
connectors for HF antennas, and push on connectors for the SWL and VHF
scanner antennas as I think the screw type provide better (tighter) and
more positive electrical connection. (K4TAX taught me about snugging up
connections early on...)
Just My take, anyway.
-------------------- K8JHR --------------------
On 7/30/2013 9:39 AM, Joel Hallas wrote:
While knife switches have been popular over the years, the big ones with
wide spacing are hard to find. My approach is to have a balanced arrestor at
the entrance panel and then I have 3/4 inch spaced banana plug and jack
between the arrestor and the line to the tuner. When I'm not on the air with
that antenna, it is pulled out and feet away from anything.
The only balanced transmit level arrestors I'm aware of in recent years have
been from ICE and mine is one of their earlier series. Their arrestor line
is handled by array solutions and they now have a new design
http://www.iceradioproducts.com/. It is also possible to use a pair of coax
type arrestors, but determine the voltage at that point on each band due to
SWR and make sure that you select arrestors that won't flashover with the
RF.
I use a similar approach for coax fed antennas. I have arrestors on the
grounded panel and then use PL-259 push on adapters on the radio side. One
yank and they're all well removed.
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