While it doesn't hurt to put protection devices at the tower it really
doesn't do too much good. Keep in mind that lightning energy on the
center conductor of coax has already made it all the way down the tower
in the coax. If it hasn't arced over by that time it will probably not
by the time it gets to the shack.
The whole purpose of the protection device is to equalize voltages on
all conductors at one place. You always want protectors at the shack
where everything is tied together (single point ground).
Yes grounding the shields to the base of the tower is recommended.
Just so some don't get confused about "grounding to a single point at
the shack". That doesn't mean that you have an elaborate ground system
at the tower base and then only one ground rod or connection at the
shack end. The shack end where the single point ground system is also
needs an elaborate ground system of its own if it is located any
distance from the tower ground system. It should also be connected to
the tower ground system.
73
Gary K4FMX
Dick Green wrote:
> Not necessarily. According to the ARRL Handbook (or maybe it's the Antenna
> Book) and Polyphaser, the optimum configuration is to install lightning
> suppressors at *both* ends -- at the tower and at the entry to the house. I
> believe the main idea is to protect the coax run between the house and
> tower, which is an important consideration if it's expensive hardline and/or
> buried in such a way that it would be hard to replace. I would think it's
> also good to have two sets of shunts to ground in case the suppressors at
> the tower get overloaded or fail. The shields should be grounded at both
> ends as well -- at the tower end to a system of ground rods and radials
> connected to the tower and at the house end to the single-point ground.
>
> 73, Dick WC1M
>
>
>>-----Original Message-----
>>From: Gary Schafer [mailto:garyschafer@comcast.net]
>>Sent: Thursday, March 31, 2005 10:14 PM
>>To: Craig Sande
>>Cc: towertalk@contesting.com; Craig Lekutis; 'Gene Smar'
>>Subject: Re: [TowerTalk] Wet setting conduit?
>>
>>
>>Your lightning protection devices should go at the house not at the
>>tower. Ground the shields at the base of the tower though.
>>
>>73
>>Gary K4FMX
>>
>>
>>Craig Sande wrote:
>>
>>>I finally decided not to risk any compromise to the base by
>>>introducing
>>>a total of 5 conduits. The pour will proceed tomorrow
>>
>>morning per the
>>
>>>original engineering. When the dust settles, I will take my time
>>>installing the conduit runs to the edge of the pier. I'll
>>
>>probably use
>>
>>>a NEMA box mounted nearby for the lightning arrestor
>>
>>devices and have
>>
>>>the conduit enter directly from below. I'll run a 6"
>>
>>copper strap from
>>
>>>the NEMA box to the tower. I'll be sure to snap plenty of
>>
>>pictures and
>>
>>>share my experience when complete.
>>>
>>>Regards,
>>>
>>>Craig, AE7I
>>>
>>>
>>>Craig Lekutis <craiglekutis@wirelessestimator.com> wrote:
>>>
>>> Craig,
>>>
>>> If it's a slab foundation and the PVC entries are not near the
>>> anchor bolts then it might not be a problem since the
>>
>>foundation is
>>
>>> probably designed for its compressive load and its overturning
>>> moment. However, if it's a pier type design, it may be a problem
>>> since it could affect interaction with the shaft and
>>
>>anchor bolts.
>>
>>> Best practice is to do what you are going to do, check with your
>>> engineer. You'll find addition information about
>>
>>foundation design
>>
>>> at http://www.wirelessestimator.com
>>> <http://www.wirelessestimator.com/> .
>>>
>>> Best regards,
>>>
>>> Craig
>>>
>>>
>>>
>>
>>
>>
>>
>>
>
>
>
_______________________________________________
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