[TowerTalk] grounding elevated vertical for lightning?

[Mark Robinson]

Could he not also ground through an rf choke to bleed off static?


Mark N1UK


----- Original Message ----- 
From: "Jeff Blaine" <keepwalking188 at yahoo.com>
To: "Jim Lux" <jimlux at earthlink.net>; <towertalk at contesting.com>
Sent: Friday, 08 February, 2013 5:28 PM
Subject: Re: [TowerTalk] grounding elevated vertical for lightning?


> Spark gap it is, then...  Thanks for all the suggestions.
> 
> 73/jeff/ac0c
> www.ac0c.com
> alpha-charlie-zero-charlie
> 
> -----Original Message----- 
> From: Jim Lux
> Sent: Friday, February 08, 2013 3:37 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] grounding elevated vertical for lightning?
> 
> On 2/8/13 10:36 AM, Jim Brown wrote:
>> On 2/8/2013 5:52 AM, K1TTT wrote:
>>> What is the best way to ground this antenna?  Can I put a few ground
>>> rods at
>>> the center base and run them up to the radial junction?
>>
>> NO! The work of Rudy Severns, N6LF, on the topic of elevated radials
>> shows that elevated radials should NOT be grounded, because doing so
>> causes radial currents to be unbalanced, which increases loss.  For the
>> same reason, a common mode choke must be used on the coax at the 
>> feedpoint.
>>
> Exactly... this was one of the interesting non-intuitive findings when
> NEC3 and NEC4 were being validated: antenna performance with radials
> alone was better than with the ground rod added.
> 
> 
> I assume you want to ground for lightning protection?  Then a spark gap
> is your friend. Open circuit for RF, but when lightning strikes, it
> closes.  Hook the spark gap to your ground rods and to your antenna, and
> you're all set.  A 1/10" gap breaks down at 7kV. Needle gap is more like
> 2kV.
> 
> 
> 
> 
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