Topband: Feedline Grounding and Feedline Chokes

[donovanf at starpower.net]

Hi Bob, 


Bonding (not grounding...) coax to the bottom of a tower helps to 
divert lightning currents from the coax shield to the ground system 
at the base of the tower 


Bonding coax to the top of the tower helps to equalize the voltage 
between the coax and the tower face. This helps to avoid pin holes 
in the coax during a lightning strike. 


Bonding all coax, control cables and all other external wiring to the 
a ground system at the entry to your shack forces the voltages on all 
of those those cables to be equal. 


None of this is related to common mode suppression. That is best 
accomplished by a choke near the feed point of the antenna. 


73 
Frank 
W3LPL 






From: "Bob K6ZZ" <bob.selbrede at gmail.com> 
To: "topband" <topband at contesting.com> 
Sent: Wednesday, March 25, 2020 10:24:11 PM 
Subject: Topband: Feedline Grounding and Feedline Chokes 

Folks, 

I see a lot of references to grounding coaxial feedlines at the top of 
towers, bottom of towers, and at house entry points. Is this purely for 
static and lightening protection purposes or does it also help mitigate 
Common Mode problems as well? 

If feedlines are well grounded, are chokes still useful for controlling 
Common Modes problems? I suspect that both can be used, and should be 
used, in a well designed station. 

Are there specific recommendations on the use of chokes on grounded 
feedlines? Does placement matter? 

Thanks, Bob K6ZZ 
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