Harold Smith wrote:
>
>> Greetings everyone. . .
>>
>> I received several responses to my email regarding installation of
>> lightning protection on my 160 meter four square. Several people
>> suggested I put a Polyphaser on the coax output of the Comtek box. . .the
>> coax going to the rig. In my case, the lightning did not enter the Comtek
>> box via the coax going to the rig (it's buried with a Polyphaser on the
>> rig end of the coax). Lightning came into the Comtek box from one of the
>> vertical elements of the array itself.
>>
>> Several people suggested spark gap arrestors, shorted 1/4 wave stubs, or
>> choke shunts (ala Array Solutions) on the elements. These approaches
>> would, no doubt, help. Unfortunately, I didn't get a firm answer to the
>> real question. Will the addition of the standard DC blocked Polyphasers
>> (basically, a big series cap) installed on one end of each coax phasing
>> line, alter and destroy the correct phasing of the array? A couple of
>> people said they thought it would but weren't sure. It would seem that
>> inserting a large amount of C in series with the phasing line would have
>> to alter its electrical length. . . and ruin the phasing in the process.
>> If so Polyphasers wouldn't work, leaving the spark gap, stub, or choke
>> solutions. Is my thinking on track?
>>
>> 73 . . . Dave
>> W0FLS
I did a quick EZNEC model and adding -4 Ohms reactance (.02 ufd)at the
feedpoint of the verticals showed no change in F/B ratio. I would also
add a robust spark gap and an RF choke to act as a static drain.
73, Roger
--
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/
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