On 12/15/2025 10:13 AM, jim.thom jim.thom@telus.net wrote:
The ICE, now Morgan arrestors work superb. They use a static drain
resistor, then a DC blocking cap, then the shunt inductor, then the GDT.
I like this circuit.
I still have a fairly large copper panel full of Polyphasers that K6XX
built for me in his shop when I moved here 20 years ago, but they're not
repairable and a PITA to replace -- it takes two people to do it, one on
each side of the wall.
I had to do it often enough that I added a panel in a large Hoffman box
using arrestors using this circuit that Array Solutions was selling.
They are repairable, and W6GJB made me some mounting brackets to make
that easy to do.
Arrestors can be blown by too much voltage across them. Like when I
transmit into the wrong antenna. Or a lightning event.
It's important to remember that arrestors fulfill two distinct
functions. First, to short the center to the shield, second to bond the
shield to the facility ground system. Because voltage is induced inside
the coax by current on the shield, arrestors must be installed in close
proximity to the receiver to protect the receiver and the station. An
arrestor at the antenna cannot fulfill that function.
AND they can't protect much of anything unless they, and the entire
premises, are properly bonded.
BTW -- in my professional life in pro audio, we had to deal with the
safety certification requirement for any installed systems that were to
be inspected, and it came to light that almost none of the equipment we
need to use for high quality systems were certified. At that time (about
25-35 years ago), there were three recognized testing and certification
agencies -- UL, CSA (the Canadian agency), and ETL (Electrical Testing
Laboratory). UL, based in the US, was VERY expensive, which was why
smaller companies didn't spend the money to get certification, and those
that did went to CSA.
The pro audio industry got together and pushed UL to reduce the costs
associated with their testing, and some went to ETL. It took about five
years, but eventually nearly all of the gear we needed to specify
carried one of those listings.
73, Jim K9YC
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