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Re: [TenTec] RFI Issues and other station high voltage precautions

To: tentec@contesting.com
Subject: Re: [TenTec] RFI Issues and other station high voltage precautions
From: Stuart Rohre <rohre@arlut.utexas.edu>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Thu, 17 May 2012 17:55:21 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
I agree on safety issues with the tuned counterpoise as I prefer to call 
it.  They are useful to remove RF from the rig metal cabinet.  But, 
they need to be adjusted for each band in use, they need to have a well 
insulated wire and run it outside the shack if possible, so that its end 
can be away from the shack.  But, you have to protect the end from 
accidental contact with anything as you must treat the end as a high 
voltage conductor which it becomes when tuned.

Also, be aware, in the case of wind induced static on either an antennas 
wire or feed line, that the feeder, even if insulated, may attain a high 
voltage that can conduct right thru insulation or such as house wiring 
devices stamped 600 volts.  Sustained wind charges up a well insulated 
dipole or double Zepp to  much higher voltages than attained when 
running normal RF levels.  Thus, insulation suited for 100 watts or 1000 
watts may pass current to someone trying to grasp a plug and unplug a 
feed line from the station.  Disconnect before a storm is within 10 
miles.  Best, to leave a station's antennas unplugged from the house 
entry point except when you intend to operate.

One case of a local ham, was that lightning struck the power line to his 
house, then entered his unused VHF rig via the power cord, and exited 
partly on the feeder and VHF vertical antenna that was much lower than 
the power line coming to the house.  Had the rig been unplugged from the 
AC outlet, it might not have been damaged, but both it and the antenna 
were destroyed along with some house wiring and all his major appliances 
that were plugged in, but off or on.

-Stuart Rohre
K5KVH
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