nanog mailing list archives
Re: Presumed RF Interference
From: Matthew Sullivan <matthew () sorbs net>
Date: Mon, 06 Mar 2006 21:17:17 +1100
Jon, Peter Dambier wrote:
Cut the ground wire in your power cords but ground the equipment directly to a metal frame.
As a time-served electrician... *****DO NOT DO THIS***** - it will kill someone.
However....You could try separate earth bonding of each components (ie connecting all the chassis together via a provided grounding terminal using nice thick copper wire), however if there is a significant earth fault even that could be dangerous (think fire) - so get a qualified electrician to do it - if there is a ground fault it will use the chassis and the bonded earths as it's route to ground.
Earth faults are often easily detectable by using a digital volt meter (Note: analog volt meters do not work for this unless there is a serious fault). First check for induced and ungrounded 'floating' voltages (any AC or DC voltage above 0.05v should be investigated), then if the DVM is fused, check for any current (amps) between chassis.
If you have money to spend before investigation find out if the building has a grounding stake and if not add one... A couple of meters of copper stake which will be connected to either the armoring of the supply cable (TN-S) or to the incoming return cable and installation earth PME (TN-C-S) - likely based what someone else in this threat said. In either type of grounding scheme the structure metal frame could (and should) be grounded (esp if exposed) which is likely to cause the phone RF signal drop. A faulty bonding in the structure (esp as it is steal) can also provide for some interesting ground faults as it is not uncommon to provide localised grounding to building frames. (In the UK where I served my apprenticeship, we were required to provide earth bonding to the copper plumbing system, additional bonding at every exposed fitting - this caused a few issues when plumbers first starting using PVC pipes)... All this said with the faults appearing with no external power and with just UPS supply, ground faults really do not 'fit' the problem - however if a generator is used also, you are in an IT type installation (electrical term 'IT' not 'Information Technology' ;-)) and will have to have a grounding stake on site.
Please note, I am trained from the UK - laws and regulations change from country to country - get a local qualified/licensed sparky to do the work or assist you.
Regards, Mat
Current thread:
- Presumed RF Interference Jon R. Kibler (Mar 05)
- Re: Presumed RF Interference David Lesher (Mar 05)
- Re: Presumed RF Interference Peter Dambier (Mar 05)
- Re: Presumed RF Interference David Lesher (Mar 05)
- Re: Presumed RF Interference Steven M. Bellovin (Mar 05)
- RE: Presumed RF Interference Scott Morris (Mar 05)
- Re: Presumed RF Interference Robert Boyle (Mar 05)
- Re: Presumed RF Interference Steven M. Bellovin (Mar 05)
- Re: Presumed RF Interference Peter Dambier (Mar 05)
- Re: Presumed RF Interference David Lesher (Mar 05)
- Re: Presumed RF Interference Martin Hannigan (Mar 05)
- Re: Presumed RF Interference Matthew Sullivan (Mar 06)
- Re: Presumed RF Interference Steven M. Bellovin (Mar 06)
- Re: Presumed RF Interference ww (Mar 06)
- Re: Presumed RF Interference Ian Mason (Mar 07)
- Re: Presumed RF Interference Andrew C Burnette (Mar 08)
- Re: Presumed RF Interference Randy Bush (Mar 06)
- Re: Presumed RF Interference Peter Dambier (Mar 06)
- Re: Presumed RF Interference Jay Hennigan (Mar 06)
- Re: Presumed RF Interference Iljitsch van Beijnum (Mar 05)