Horizontal long wire MW aerial.

[ppppenguin]

Yes. Because the purpose of equipotential bonding is to ensure that all exposed metalwork remains at the same potential during a fault.

There are discussions to be had on details. For example I don't think you need to bond a metal sink fed by all plastic plumbing as the chances of it becoming live are minimal and it's more or less insulated from anything else.

[pwdrive]

From the RSGB on the subect:

http://rsgb.org/main/files/2012/11/EMC07...-Basic.pdf

http://rsgb.org/main/files/2012/11/UK-Ea...v1.3a-.pdf

Lawrence.

[Crackle]

I see what you mean, in that circumstance yes I would.  
So what you are saying is, I am obliged to connect my nice new clean earth back to the mains earth.
So will fitting this earth make any difference at all to the RF signal from the new aerial, and will it help give a cleaner less interference signal?

The reason I thought I would fit a new earth was because I have noticed that interference is reduced a little if I disconnect the mains earth from the radio.


Thanks
Mike

[Terry]

This is pure guesswork, Mike, but could work.

The mains earth is a long wire running round the house in very close proximity to the live wire. The earth wire must have some inductance which, while it doesn't affect its function of conducting fault currents to ground, with have an impedance to earth for all RF interference injected into it - primarily, I would expect,  from the adjacent live wire.

If your new earth is effective, if you take a second wire from the earth rod itself and connect that to the mains earth in the house, any interference on the mains earth will be conducted directly to earth and not appear on your new receiver earth wire.

However, there may still be a common connection if both earths share the same physical path from the house, so it might be worth using a length of coax for this section, connecting both centre conductor and screen at the earth rod but only the centre conductor at the house end. The woven screen should have a low impedance to any interference picked up on it and, of course, you will now have two capacitors in series between the two earths which will also reduce any pickup.

It might also be worth stripping the outer sheath off the coax and ensuring that it is bedded well down into the soil beneath the concrete.

Worth considering?

[pwdrive]

What if the supply is PME and the neutral fails, possibly a heap of current going through a wire that you wouldn't want it to.

Lawrence.

[Murphyv310]

Hi Mike.
TBH I don't think some of this is hugely relevant to what you are doing. I realize I'll get the experts giving me flak which I accept.
What I do with long wires is to use a 1:1 or other suitable ratio RF transformer matched for the input impedance of the radio. I wind my own ones on ferrite rings using single core insulated wire. Thus electrically isolated from the mains side to the aerial and earth.
One winding to the long wire the other end of it to the earth rod. The opposite winding to the radio input (aerial & earth)
Safe as houses and no inference on the mains earth.

[Murphyv310]

Hi.
Any further worries about safety can be addressed by fitting two 100ma fuses, one in each leg of the secondary, I would use Wickman fuses in this case.

[Crackle]

I have tested the resistance of the mains earth in my room to the central heating pipe, (mains socket and CH pipe) and taking into account the 0.3 ohms meter lead resistance, it is 0.4 ohms.
I have also checked the voltage between the 2 earth points, (again mains socket and CH pipe) which is anything from 1mV AC to 2.5mV AC, on DC it measures 0.1mV.

In the past I have used the CH pipe as an RF earth and it seems cleaner than the mains earth, but as it is connected all around the house well above ground it also works very well as an aerial, so how efficient can it be as an RF earth.

How about if I connect a second substantial wire (16mm) from the new earth rod to the central heating pipe in my room, (that is a lot more convenient than having all the floor boards up all over the house to feed another earth wire back to the mains consumer unit) and another wire from the new earth rod to my radios.
Any fault currents should be able to be handled by either wire.

I would hope that by bonding the mains earth (CH pipe) to the new earth rod, that any interference on the mains earth would have better path to ground.

Does this sound safe and would the new earth help the radio signals with the aerial proposed in post #22 ?

Thanks
Mike

[Murphyv310]

I'd not connect the earths together at all as it can increase noise. If using the RF transformer you can try the mains earth on an AC set and compare the noise level with on or off. The other advantage of the transformer is sets that already have the earth connected via the plug as two earths like I say can increase noise.

[Murphyv310]

Sorry Mike. I'd not be feeding the earth to consumer units or radiators, your negating the effect of a separate earth. I know all the reasons mentioned above but it's totally pointless if you want to reduce the effects of noise from SMPS Etcetera. Mike, give the tranny a whirl I think you'll be impressed, it's the best method to gain the best from your earth rods.