Old style earthing connected to roof aerials

Joined
18 Oct 2013
Messages
1,098
Reaction score
10
Location
London
Country
United Kingdom
I just remembered that our old 1930s semi detached house used to have some thin wire cable running down the side of he house into the front garden. I think one end may have been attached to their aerial should a lightening strike it.

1. Do houses still get built this way?
2. If an aerial was struck, would the wiring have done any good?
 
Sponsored Links
Possible an "earTh for an overhead telephone line Protector Terminal Box

In the good old days overhead telepone lines has fuses and transient voltage suppressors fitted where the cable entered the house. These required a thin cable to ground. Party Line telephones ( two subscribers, different numbers but sharing the same copper pair ) needed an earth for signallong to the exchange which subscriber wanted to make a call.

0X41.jpg


If an aerial was struck, would the wiring have done any good?

The wire would vapourise very quickly as the discharge current built up and the metal vapour might then create a path for a plasma discharge along the route of the wire and thus outside the building.
 
If an aerial was struck, would the wiring have done any good?
Absolutely - it would have done the strike good, insofar as it would have helped it happen by taking an earthed pointy thing closer to the clouds.
 
Sponsored Links
Any bend in a lightning conductor oresents a high impedance to the rapidly rising and falling currents in the strike. This high impedance creates a voltage spike which can cause the current to jump to a near by conductor.

A loop in the aerial feeder and a gounded plate next to the loop is believed to be an effective way to protect equipment inside the equipment room.

0x45.jpg
 
Last edited:
I assume the insulation needs to be removed from the black, near the green earth for the current to jump across
 
Any bend in a lightning conductor oresents a high impedance to the rapidly rising and falling currents in the strike. This high impedance creates a voltage spike which can cause the current to jump to a near by conductor.

A loop in the aerial feeder and a gounded plate next to the loop is believed to be an effective way to protect equipment inside the equipment room.

View attachment 152887
Yes this is something that used to appear in publications but I don't recall seeing it in recent times, it's not applied on any of the aerial masts I've worked on, however the feeders are bonded to the mast or some other point of the earth arrangements at the aerial, at the point it leaves mast towards the cabin and at the point it enters the cabin, commonly into a gland plate. Additional bonds are used if the mast is particularly tall.

The lightning conductors on buildings would have typically been formed into curves when rods were used to go from, say, a horizontal run to vertical but now with the flat bar they just cut and clamp together at right angles.

These are my observations and not 'the rules', which may be two very different things.
 
I guess that would explain the thick insulation kV cable has
You need quite a lot of kV to need particularly thick insulation. The dielectric strength of PVC is around 15-20 kV/mm. Most other 'plastics' (polymers) are similar, other than PTFE which has a dielectric strength about 3 times greater than that.

Kind Regards, John
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top