Can I add earth rods to my incoming setup?

[OwainDIYer]

having 22" walls and solid floors make it no small task. :

Decent SDS drill and drill bits will get there (eventually)

 

[JohnW2]

But I want to put it much higher and for the lower bands, possibly multiple wires. Problem is that I have 55' from chimney down to the back of the property.

Sounds a bit worse than some of mine:

Untitled

• JohnW2
• 4 Dec 2012
• 2

Am off to a rally in Sale in the morning to get some bits, a center & some insulators - a balun if I see one cheap enough etc.

Happy shopping! Most of my activity, albeit mainly in the dim and distant past, was on VHF/UHF - so a whole different set of antenna issues!

Kind Regards, John

 

[DetlefSchmitz]

Long time since I was active. But since then I believe the RSGB have since published a number of papers covering the earthing problem. It might be worth googling them. They may cover things you hadn't thought of.

 

[JohnW2]

Long time since I was active.

Quite possibly not as long as in my case - my 'peak' was probably mid-60s to mid-70s It was brought home to me when I found myself in the published list of those with 50 years continuous RSGB membership a year or two ago!

Kind Regards, John

 

[DetlefSchmitz]

Quite possibly not as long as in my case

Mmm.. you might have a slight edge on me.

Congratulations on the RSGB membership. I let mine lapse, or I might have been on the list.

 

[JohnW2]

Mmm.. you might have a slight edge on me. ... Congratulations on the RSGB membership. I let mine lapse, or I might have been on the list.

Thanks. I'm actually not quite as old as it might sound - rather, I was somewhat 'precocious' and got my licence on my 14th birthday (having had to wait until I achieved that age to be 'eligible'!).

Kind Regards, John

 

[mattylad]

I'm being a born again ham, ticketed in the 90's then kids came along.

Now trying to play on HF on a wet shoestring.

Your chimney is a tad higher than mine although I wouldn't want to be pulling it with an antenna wire unless it had something pulling it back also.

I'll get there in the end. baby steps

 

[JohnW2]

I'm being a born again ham, ticketed in the 90's then kids came along.

Similar kids issue here, but I never really had a renaissance in any serious way. By the time that might have happened, the world had 'moved on' so far that many of the attractions and appeals which has existed in the 60s and early 70s had largely evaporated!

Kind Regards, John

 

[ericmark]

543.1.1 says 4 mm² min for protective conductor don't know if this has now changed.

I actually saw the results of an earth mat connected to TN-C-S earth when road works severed the combined neutral/earth the 4mm² cable became copper beads on the ground. As a result his shack was made TT which cured the problem but he had also gone rather OTT with earth rods and tape for shack.

At 10Ω or above for the earthed metal you will not get enough current to melt the 4mm² cable. His earth mat was more like 2Ω which is extremely low.

I have not used HF with my UK licence I did as a VP8 but not as a GW7. When I was active in UK and Hong Kong "VR2" I used packet radio and as a VP8 I used a tri-band three element yagi and long wire for 80.

I left RSGB to become a founder member of UKRS which folded but still got what we wanted and I can now use HF with my licence.

I have put in earth rods under a floor. but reading was 60Ω as so dry.

 

[JohnW2]

543.1.1 says 4 mm² min for protective conductor don't know if this has now changed.

It still does (or 2.5 mm² if mechanically protected), but that's just for protective conductors in general. However, here we are talking about a Main Protective Bonding Conductor, and 544.1.1 specifies the minimum for that of 6 mm² (or 10 mm² minimum if PME)

I have put in earth rods under a floor. but reading was 60Ω as so dry.

Indeed. It was the potential dryness which led to the uncertainty I was expressing about 'under house' earth rods. Probably OK for a TT earth, but hard to get a decent low impedance for an RF one- so hence my comments about the alternatives to RF earths.

Kind Regards, John

 

[ericmark]

I stand to be corrected but my understanding is an earth rod in a house with a TN-C-S supply is not called a protective earth electrode it's called an extraneous-conductive-part if you can touch it from outside the house and an exposed-conductive-part if you can only touch it inside the house.

Hence why some say you can't fit an earth electrode with a house with a TN-C-S supply you can physically fit the rod but it's not called an earth electrode.

In one job we had a huge resistor between the DNO supply earth and the site earth I would assume a very low value it was around 6 foot x 4 foot x 4 foot in size so clearly could dissipate a lot of heat. The earth pit had four rods at 8Ω each linked with 180mm² bare copper which was back filled plus around another 100 earth rods throughout the site at 8Ω or less I had to sink between 3 and 7 earth rods at 1.2 meters each to get an 8Ω reading. Very sandy soil.

Since I have done very little with HF I can't really say what earth is required for the radio but really you would not want the radio connected to DNO earth directly as it could cause signal to be radiated from DNO cable into other properties.

I have seen another way to connect a TN-S or TT earth this time to a boat in fresh water and this was in essence a pair of diodes back to back allowing a PD of 0.6 volt between boat hull and shore earth to stop electrolysis. I would be wary of diodes in the earth as I remember how the rusty bolts in an aerial mast caused loads of interference as the rust acted as a diode. But it is clearly permitted to put devices between earth wires to limit both voltage and current.

As you have said the RSGB (Radio not Research Surveys of Great Britain) likely has advice.

 

[JohnW2]

I stand to be corrected but my understanding is an earth rod in a house with a TN-C-S supply is not called a protective earth electrode it's called an extraneous-conductive-part if you can touch it from outside the house and an exposed-conductive-part if you can only touch it inside the house.

Unless I'm going mad, that is surely all "upside down and back to front". The whole point (and danger) about extraneous-c-ps is that, if not Main Bonded, they can result in the inside of the building not being an equipotential zone, hence possibly containing dangerous potential differences between various conductive parts. It is surely the case that any conductor which appears out of the ground and enters a property must be regarded as an extraneous-conductive-part, and therefore needs Main Bonding.

Hence why some say you can't fit an earth electrode with a house with a TN-C-S supply you can physically fit the rod but it's not called an earth electrode.

It doesn't matter what the earthing system is, or what one calls the rod - if it (or an extension of it) enters the building, then it surely represents an extraneous-c-p, which could introduce potential hazards into the premises. In practice, that's not usually an issue/problem, since if it's being used as an earth rod (connected to the installation's earth), the CSA of the 'earthing conductor' will usually be required to be at least as great (usually greater) than that required for Main Bonding. As per this discussion, an exception might exist if it were not being used as a supplement to the installation's earth but, rather, only as an 'RF earth' for equipment which essentially isolated it from the installation's earth (at least as far as 50Hz was concerned). If one did that, without Main Bonding, it clearly would represent a potential danger, since the building would no longer necessarily be an equipotential zone.

Since I have done very little with HF I can't really say what earth is required for the radio but really you would not want the radio connected to DNO earth directly as it could cause signal to be radiated from DNO cable into other properties.

As above, it would be difficult or impossible to have an earth which was not connected to the installation's earth directly connected to equipment within the building (as an 'RF earth') without creating a possible shock hazard. However, I imagine that the 'RF earth' could be effectively 'isolated' as far as 50Hz was concerned by inductive coupling (or even perhaps just a small capacitor) outside of the building. That would obviously be difficult for the OP, given that his earth rods will be entering the property through the cellar floor - but I suppose they could enter into insulated enclosures with the "50Hz isolation" within them.

As you and others have said, the RSGB have written a lot of this over the years/decades. It's never really been much of an issue for me, so I haven't taken much notice of it, but I'm sure that the material, and advice, is 'out there to be found'.

Kind Regards, John