Lightning Protection, feedpoint? - run to ground in what?

[VE7ORA]

In the process of constructing an ccean side Cabin (wood construction) on high bluffs in an area subject to Lighting. Need help answering th e most basic of questions.

Antennas for:

- yaggi cellular bridge
- WiFi covering property
- VHF/VHF
- FTA/Broadcast Sat

I am thinking about installing inline Coaxial Gas Discharge Tube Surge Protectors, with a good run to earth ground.

Questions:

1. Am I correct in assuming that the Surge Protectors should be located at the Antenna end of the run, as near to the assumed source of strike?

2. Ground runs, what type of conduit should these run in, passing through two stories of wood framed construction. Concern is potential fire risk, or peripheral lateral discharge to nearby components or cabling.

Thoughts?

 

[VEBill]

Traditionally, the lightning protection devices are located at the point where the cables enter the structure.

The typical illustrations, drawn in the 1970s or earlier, tend to assume that the cables run down the exterior to an entrance point near the ground, and with a very short run from the protection device to a good ground system.

The problem with this old tradition is that modern systems use much higher frequencies where cable loss is an issue and there's no point running (for example) your WiFi 2.4 GHz RF cable an extra 80 feet - there'd be no RF left at the far end anyway unless you used very expensive cable. So you're left with bringing the cable in where appropriate and having a longer run to ground.

Reducing the risk of fire would seem to be much easier than preventing equipment damage. Follow code.

The WiFi antenna could probably be indoors. The satellite dish could be installed well down from the peak of the roof. Perhaps the Yagi for the cellular could also be installed slightly lower.

Leave the Ham V/UHF antenna up high, use excellent grounding and pull the plug on that system when you're not using it.

PS: FTA, or "FTA" ?

 

[BrianR]

You certainly have your work cut out for you here. Lightning prefers to strike edges like bluffs so it is a risky position.

Do provide the lowest resistance ground possible so if the soil allows it then drive a series of (eg)3 ground stakes as deep into the ground as possible. (A depth of 6' - 10' if you can do it). Space the stakes by their own length and interconnect with heavy copper cable. You can buy copper stakes that screw together is sections from suppliers of electrical hardware.

The arrestors should be installed as VE1BLL suggested but the provision of the connection from them to ground is critical and I think a coaxial conductor is often used but here are some useful web sites.

http://www.lightning.org/

http://www.lpi.com.au/

http://www.ecoptions.com.au/

 

[whycliffrussell]

put a 90 deg bend in the cable that enters your building. this will also help to provice a path for the lightning to 'exit' the cable, enter the gnd and not your building...this is quite common in these types of installations...ie: (excuse the crude graphics).

\
\
\ Y <-Antenna
\ |
\ |
\ |
\ |
BUILDING |
| |
| |
| |
| |
| |
|----/ <----bend in cabe entering building
| *<-Lightning will 'arc' here and entern ground
--------------------------GROUND

 

[dpc]

A little light reading:

http://www.polyphaser.com/ppc_ptd_home.aspx