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Dirty and clean earths

Postby ericmark » Sat Jan 12, 2008 12:24 pm

Radio armatures using HF in order to prevent RF finding its way into neighbours TV and radio need a good earth which is not connected to any common earth. The method was a “Shackâ€


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Postby sparx » Sun Jan 13, 2008 10:14 pm

Hi ericmark, not sure if there is a question in there or just a statement...
but this radio AMATEUR [G6NLZ] licenced since 1982 has used the following system for my own 'shack' seperate from house.
Pyro feed to plastic con.unit,no earth connected. Earth rod on one side of shack to con. unit for mains circuits, all radio equipment supplied through double wound isolating transformers with secondary side to an extensive earth system of rods/tapes to a central earth bar to which all antenna earths connect in star config. so as not to set up loops, also three section 'crank-up' tower bonds to same point.
room is all insulated construction, & when running @'full-legal-power' hair stands on end, what a great hobby!!! never get visits from -der boss lady-
too scared to enter....ho ho
regards SPARX
Rank: Project Manager
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Postby ericmark » Sun Jan 13, 2008 10:45 pm

Thanks for info. Seems a good set up. Unlike you I (VP8BKM VR2ZEP and GW7MGW) have been using the 2 meter band in the main, and have not set up anything for HF and was considering doing that now. I had used HF as a VP8 but not in UK I had not thought about isolation transformer that would cure a lot of problems. We started about the same time VP8XBHZ was first license before I got HF one. But it was about 1991 before I took RAE and got UK license (Can't call it British as already had British one). But I looked at BS7671 and I could not find regulations as to not using the earth provided with the TN-C-S supply. And unlike you I will have to deal with some council official who will have little knowledge and will want to go by the book. Although I know what I need to do I can't find regulations that allow it. I left RSGB when UKRS started maybe I need to re-join or maybe joining IEE or what ever its new name is would be better?

73 Eric

Postby sparx » Mon Jan 14, 2008 9:25 pm

hi agn ERIC, when i operated 2Mtrs ran 100W to 2X16 element stacked yagis used TN-C-S earth with no probs at all, even with antenna array pointing at own tv aerial some 10 ft away, only slight audio breakthrough on peaks (ssb mode).
Only changed set up when started HF experiments with various aerial set ups, wanted consistant results from known ground mat for comparisons between say multi band vert, & trap crossed wire dipoles both in use @ moment.
Top of tower has 6mtr 2 element tringular loop beam, great band when open, modified 'sandpiper' design published in Radcom.
73's may meet on air one day!
Mac G6NLZ (JO- 00- kw/AK05J)
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Posts: 2166
Joined: Wed Mar 21, 2007 8:33 pm
Location: The fifth continent.

Postby ericmark » Tue Jan 15, 2008 4:27 pm

By George I think I got it. 413-02-17 If a residual current device is used for automatic disconnection for a circuit which extends beyond the earthed equipotential zone, exposed-conductive-parts need not be connected to the TN system protective conductors provided that they are connected to an earth electrode affording a resistance appropriate to the operating current of the residual current device. The circuit thus protected is to be treated as a TT system and Regulations 413-02-18 to 413-02-20 apply. Even if it doesn't I would not think man from council will ever work it out!

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