[TowerTalk] Feedline (choke) question

[Jim Brown]

Exactly right. In the words of the late Neil Muncy, W3WJE, a great 
engineer who in 1995 recognized "The Pin One Problem" as the major cause 
of RFI, "The earth is not a sump into which hum, buzz, and RFI is poured!"

What solves all of the problems being discussed is BONDING! That is, the 
connecting together of every earth connection and every chassis by 
short, fat copper. That, in addition to an earth connection at power 
entry, and at any outbuildings, is required by LAW -- that is, Local 
Electrical Building Codes, the model for which is the National Electric 
Code, written by a bunch of very smart engineers. The earth connection 
is ONLY for electrical safety and lightning protection, and Bonding is a 
critical part of that.

More wise words from Neil Muncy at one of his workshops in Chicago. 
"Park at the end of  runway out at O'Hare (substitute your local large 
airport), and call me collect when you see an aircraft taking off 
trailing a ground wire!"

I was paid to teach this stuff to electrical contractors who install 
sound and video systems for large and small facilities, taking over that 
gig from Neil when he was no longer able to do it. My slide decks for 
that are here.

http://k9yc.com/InfoComm-PowerSystems2012.pdf
http://k9yc.com/InfoComm-Grounding2012.pdf

I was also commissioned to write a "white paper" on the topic. This is 
the international version, which includes a section on the differences 
in how power systems are done in the UK and EU.

http://k9yc.com/SurgeXPowerGround.pdf

And these are slides for talks I've done at Pacificon, Visalia, and to 
several large clubs. http://k9yc.com/GroundingAndAudio.pdf

Most recently, I worked extensively with Ward Silver, N0AX, on both 
versions of his excellent ARRL books on the topic.

ALL of this is nothing more than applied fundamentals. One of the best 
parts of my education was a 3-day workshop by the late Henry Ott, a 
veteran of AT&T Bell Labs, who consulted on EMC to dozens of the major 
corporations.

Jim Thompson -- bonding on the tower you describe is textbook correct -- 
that is, a serious choke at the feedpoint, running coax/hard line down 
the inside of the tower, bonding shield to the tower top and bottom. 
That bonding is for lightning protection for the feedline -- failure to 
do that can result in arcing inside the feedline in the event of a 
strike. Many years ago, I found a piece of Andrew 7/8-in at a 
decommissioned AT&T Long Lines site where I had a station for a while 
that had exactly that fault. I discovered the fault when I tried to use 
it in my station at home years later.

73, Jim K9YC




On 9/27/2025 11:07 AM, David Gilbert wrote:
> That's a fallacy.  It simply isn't.
> 
> Dave   AB7E
> 
> 
> On 9/27/2025 10:31 AM, Brian Beezley wrote:
>> I've always thought of ground as a current sink.
> 
>