Hardware Chat

its interesting, as like you i am a graduate of essex ham and have completed my intermediate (doing full exam at end of the month)

the courses all cover earthing but from a safety in the shack aspect, and reducing RFI / EMC and not much other than a few minor references for static / lightning protection 

all the bits i have read say the rig and other equipment in the shack should be connected to an "RF Earth" which is separate from the mains earth (but there are exceptions with PME systems)

i have seen references in the Full exam manual (pages 16-18) to high value resistor, or old spark plugs for static protection but no real general guidance as to when or if it is required

there are also a references to EMC Leaflets - Radio Society of Great Britain - Main Site : Radio Society of Great Britain – Main Site (rsgb.org) for more information on page 18 of the full exam manual

there is lots of contradictory information on the net, so like you i am interested in what the more experienced Hams think on the subject

Peter

2E0PWX

Greetings Peter 2E0PWX,

Fellow travellers indeed!  I shall be some low number of weeks behind you for the Full with any luck, and should I continue to study well.

I don't yet have an HF rig, I'm on back order for the Yaesu FTDX10 which will hopefully come in early March (I only aim to get one [bet I'm not the first to have said that]).

However, in advance of receiving that kit, I do have a Thunderpole CX-201 PL259 2-Way Antenna Switch which I now do have grounded to a separate earth copper spike outside, as I believe this will in any event be needed for HF operations.  So at present, and following my previous experience, the chassis of my UHF/Base station is connected via the screening on my RG213 jumper to the grounded switch, and the antenna is therefore also grounded via the feeder screen and the switch to that separate RF Earth (I am in an old none 'PME floating' abode).

I don't aim to be transmitting at more than 100W in any event in the near future, and have seen a post by ARK at Bleeding off static from a vertical | Page 4 | QRZ Forums which looks like an intriguing way to handle Van De Graaf static using a bleed resistor.  At this stage for Thunder and lightning I'll just take down/disconnect any antenna, but would like to consider that more closely when and if I put something permanent in. 

Again though, I'm kinda experimenting and guessing here, and am intrigued to see what others think.

73 for now,

William 2M0WKO

Hello,

So I believe I have gained a little further understanding (please don't take anything discussed here as advice, merely  a search for understanding).

The two things we want to cater for in our shack environment, for electrical safety purposes, are Voltage and Current.  Grounding is about keeping current away from our equipment AND keeping everything at the same voltage level.

In an old house like mine where I can see the massive earth wire coming in with the power supply to my 1920's house, so I do believe I have a TN-S type installation. 

A main reason that we would want equipotential bonding of any earth for our shack equipment to the main earth for our house is to avoid there being a potential difference between conducting surfaces e.g. bare metal of our mains grounded a.c. power supply, and bare metal on say our shack equipment.  If our body bridges the gap between those metal surfaces and sufficient p.d. exists then a potentially dangerous current could flow.

I had previously only seen/reviewed this:

Microsoft Word - EMC07-v4-Earthing-and-the-Radio-Amateur-Basic.doc (rsgb.org)

It turns out the RSGB has an excellent document covering this (was in list at link provided by Peter 2E0PWX):

Microsoft Word - UK-Earthing-Systems-And-RF-Earthing_Rev1.4.doc (rsgb.org)

Section 4.1 states we can minimise risks by e.g. Using earth free antennas (balanced feed) and use trees or fiberglass masts for support (I use these). If we use a vertical dipole then choose one which is mounted free from earth (so this ties in with the previously referenced Slim-Jim earthing advice.

So, as I understand it having attempted to absorb the RSGB document, with my old supply type, and not having a permanent/earthed tower, if I have my DC-Side shack equipment earths connected to a common bus to an external ground rod (btw the Americans appear to think two rods are better), then I don't necessarily need the bonding, nor the Part P qualified electrician to inspect and approve my installation (once current restrictions are gone I think I'll engage someone to review).  This should allow e.g. any common current coming down the feeder to go to ground thus avoiding RF in my shack.

I am separately considering anti static protection in the form of a bleed resistor to handle precipitation static which is what I think I experienced in my OP here Bleeding off static from a vertical | Page 4 | QRZ Forums. 

I do hope this discussion is of value to others and wish everyone well!

Regards, William 2M0WKO

My understanding on this subject grows in leaps and bounds and perhaps I coulda, woulda, shoulda reviewed lots of things before originally posting, but then I was hoping to provoke a conversation …

As always my comments below are in no way to be relied upon as advice or guidance, but rather as an exploration of this subject area (but my understanding feels very much improved) …

I’m focusing on the basics of grounding and bonding with a properties Main Earth Terminal MET, and how handling RF directly relates to that in what I’m calling a typical domestic situation. 

Electrical Safety:

We talk about earthing and equipotential cross-bonding.  Earthing protects us from electrical shock by providing a low impedance path (protective conductor) for any ‘fault condition current’ to flow to earth (and hopefully also blow the fuse or in a modern house trip the circuit breaker) via e.g., the Main Earth Terminal MET of a property.

Bonding reduces the risk of electric shocks where someone might provide a circuit by touching two metal surfaces when there is a fault in the electrical supply, so e.g., bonding metal pipework in the home to the MET.  It does this by ensuring these surfaces are actually at the same voltage level.  As an aside, if one device surface were at a potential of a million volts, and another was also at a million volts, then there would be no voltage delta between them, and if e.g. I bridged that gap by touching both equipment enclosures (please don’t try this at home), then no current would flow as there would hopefully be no actual difference in their voltage level. 

I believe that in a typical domestic setting, it is sensible for most of us, to have our station earth path bonded with our main house supply earth path by a Part P approved Electrician Microsoft Word - UK-Earthing-Systems-And-RF-Earthing_Rev1.4.doc (rsgb.org).  In an old house with an old TNS supply like mine this ‘may’, arguably not be a legal requirement in the UK.  I believe that it is illegal to operate in the United States without bonding the shack and house earth paths, in a typical domestic setting.

We further protect ourselves by using:

Circuit breakers, which are an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit.

Residual Current Devices to supply our shack power, these typically can detect currents as low as 10mA flowing between the mains live and neutral conductors, and shut of the electrical supply should this fault condition arise.

Introducing RF:

RF Currents that flow back through our feeder lines or are picked up by cabling etc. are at much higher frequencies than our mains supply. 

Bonding materials like copper conductors have what is called a skin depth What Is the Skin Effect? | Reactance and Impedance -- Inductive | Electronics Textbook (allaboutcircuits.com). At a frequency of 10MHz a length of 10-guage earth wire with a DC resistance of 25 Ohms, has an AC effective resistance of 2.182K Ohms, Blimey!  This is one reason we see the use of big hollow copper pipes and/or wide flat straps for earth connectivity in an RF Station.  If you don’t have that, use heavy gauge Multi-strand cable to start with (but improve if/when you can).  Solid core, large gauge wires are not a good choice.  Fat connections are more conductive / less resistive, and short connections have lower inductive reactance, so overall minimising impedance.   Please also keep in mind something is better than nothing.  Avoid mixing different types of metals in the bonding path.

Bonding for our shack should therefore be done to a common earth path using the shortest, straightest and lowest impedance connections we can, preferably to a single point, thus minimising impedance and ground loops (connectors in effect being mini-inductive coils that develop impedance at RF).  The bonding path should not be daisy chained through the equipment.  It should be bonded to the MET. This ensures an equipotential voltage level for all equipment surfaces with respect to the MET and to each other.

All conductive items in the shack are an antenna equivalent and can pick up RF through coupling, so we should add common mode chokes to all none-bonding wiring to minimise RF pickup.  RF chokes will also minimise static build up (something also done by e.g., those little corona balls we see at the end of many whip antennas).

If we don’t bond our RF earth path (e.g., the conductor path to the earth rod I’ve knocked in) to our MET, then a ‘shocking’ potential difference ‘could’ develop at RF between my Station Equipment and e.g., my radiators, there being no mythical Zero level voltage in the earth itself.  Please see the table about half way in the linked article showing the massive voltages that can exist with long wires at RF, and compare these to your domestic supply voltage…( Grounding Systems in the Ham Shack - Paradigms, Facts and Fallacies – FlexRadio)

Lightning Protection, RF and Static:

Paths for lightning to ground should be outside the house, and as before be heavy Gauge and Low Impedance (lightning behaves like RF on wires [reactance]), so short and fat.  They must NOT go through, but around/past the station/shack on the way to ground.  Most lightning energy centres around 1MHz (ranging from 100KHz to 10MHz).  Where an outdoor antenna is not typically disconnected when unattended, a lightning suppressor should be fitted.  For most of us standing waves, common currents and static are the main things we want to handle; once we have towers and so on things require a little more thought…

Slim JIM:

The Slim Jim is a vertically polarized, omnidirectional, end-fed half-wave antenna with a quarter wave J-Type matching stub (J Integrated Matching), and should be totally insulated, and a quarter wave free space from any mounting mast (mine is fibreglass).  Apparently, no part of the antenna should be grounded.  My feeder line has an electronic path to earth via the coax screening just before it enters the house.  I’ve found I definitely need some good ferrite RF chokes near the antenna (SLIM JIM ANTENNA PROJECT (hamuniverse.com)), especially during a heavy snowstorm.

There’s just so much stuff for us to absorb in this hobby even just on this narrow subject area, if we want to, and of course, I’ve only scratched the surface.

I think I, happily have much more understanding in this area now, and this book in American-ese gives a ‘very’ good background for US amateurs, and there’s a handy guide by G6GPF linked for brits to interpret…

ARRL Grounding and Bonding for the Radio Amateur - Radio Society of Great Britain - Main Site : Radio Society of Great Britain – Main Site (rsgb.org)

Lastly I’d like to recommend another American book by the same author that I’m finding incredibly informative with regard to the hobby in general, modes, competitions and general jargon, despite its title, it’s Ham Radio For Dummies (For Dummies (Computer/Tech)): Amazon.co.uk: Silver, H. Ward: 9781119454847: Books.

No end to learning in sight, but understanding increasing, and that’s not a bad thing…

William (2M0WKO)

Very interesting, certainly been doing your research, lots of links for additional reading

my antenna will be moving from on my fence to 4-5m in the air, so i guess at that point i will start suffering from the issues of static, so watching and reading this topic with interest

my 2m/70cm antenna is a std white stick with the antenna inside a sealed fibre glass case, which seems to shield it from the static issues

so one question if you have a transformer balun (not a current balun for dealing with common mode issues) do you still suffer static? if not is that yet another reason for a balun along with impedance matching?