[Elecraft] K3/100 -Second floor- no RF ground ??

[Don Wilhelm]

Steve,

Just don't "bet your life on it" - the difference between stranded and 
solid wire will be minuscule for a lightning surge.

Good surge suppressors for every feedline are a must here in North 
Carolina, and most other parts of the world.  If you do nothing else, 
get some gas discharge tubes and solder them across the antenna feedline 
at the point where the feedline enters the building.  Bournes 2027-35-B 
are rated for 350 volts DC and 600 volts sparkover - that should be good 
up to about 1000 watts.  For higher power, two in series should do the 
job.  These are only $1.36 each in single quantity from Mouser (catalog 
page 591).  For parallel feedlines, use one on each side of the line.
To be effective, the coax shield  (and surge suppressor) should be 
connected by a good conductor to a good ground system at the entry 
point, failure to do so will reduce the effectiveness of whatever type 
surge suppression is used.

What do I use?  I have polyphaser suppressors on each coax line - but 
that is 150 coax feet away from the shack, so I add gas discharge tubes 
at the shack end for additional safety.  At each point, I use wide 
copper strap to connect to the ground system - 1/2 inch of width for 
each coax.   All control lines have Varistors to ground at each end.  
The ground 'window' is a 16 inch square of copper sheet purchased from 
McMaster-Carr.

73,
Don W3FPR

Steve Ellington wrote:
> Don:
>
> You answered my question when you said:
>
> "In fact, I would think that an antenna that has higher resistance to
> lightning surge is better - the strength of the surge will be reduced by
> the time it reaches the shack. "
>
> I have never seen this issue addressed.
>
> So bottom line:
> Using stranded wire for antennas improves ligtning protection.
>
> Steve
> N4LQ
> ----- Original Message ----- 
> From: "Don Wilhelm" <w3fpr at embarqmail.com>
> To: "Steve Ellington" <n4lq at carolina.rr.com>
> Cc: <don at w3fpr.com>; <n1al at cds1.net>; <elecraft at mailman.qth.net>
> Sent: Thursday, February 25, 2010 12:13 AM
> Subject: Re: [Elecraft] K3/100 -Second floor- no RF ground ??
>
>
>   
>> Steve,
>>
>> That is a bit of a strange question - because I never though of my
>> antenna wires as being a conductor for lightning.  While the antenna
>> wires will pick up lightning surges, I don't think that is what is being
>> considered.  What they are talking about is how to dissipate whatever
>> lightning surge that makes it into the shack to ground.  For that - yes,
>> you would use solid conductor (of heavy guage) wire, or better yet flat
>> copper strap with its large surface area for the station safety
>> ground.   Conduct the energy out of the shack and into the earth ground
>> where it can dissipate.  The greater earth surface that you can
>> distribute that energy, the better - be that several connected ground
>> rods separated by twice their length or a system of buried conductors
>> like a perimeter wire around the building where the shack is housed.
>>
>> In fact, I would think that an antenna that has higher resistance to
>> lightning surge is better - the strength of the surge will be reduced by
>> the time it reaches the shack.  The path from the shack to your
>> lightning protection ground is a different matter, and should be low
>> impedance at all frequencies if that is possible - it is not, so we do
>> the best we can with conductors having greater surface area and plenty
>> of conducting capability for high currents as well.
>>
>> So stranded wire is OK for antennas, but not for the run from the
>> station to the safety ground.
>>
>> 73,
>> Don W3FPR
>>
>> Steve Ellington wrote:
>>     
>>> Speaking of lightning grounds. MFJ says use soild wire or flat copper for
>>> ground wire and never use stranded or braided wire. They claim the latter
>>> has high impedance to lightning.
>>> Ok, fine....so if my antenna is stranded wire, does it have high 
>>> impedance
>>> to lighting? Would it be less safe to make ones antenna from solid
>>> conductors? Yes...a weird question but it's been bugging me.
>>> Steve
>>> N4LQ
>>>
>>>
>>>       
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.733 / Virus Database: 271.1.1/2708 - Release Date: 02/24/10 
> 14:34:00
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com 
> Version: 9.0.733 / Virus Database: 271.1.1/2707 - Release Date: 02/24/10 02:34:00
>
>