Red Wave Radio

So any one got some pointers or helpful hints on installing a separate
station
earth. The ground connection is easy 3 to 6 off 6' long 1" dia copper pipes
driven all the way in to the soil (I know it is a big is job but not
impossible).
The bit I am puzzling over is do I use a heavy copper strap as used on
church
lightening conductors to provide a common earth for every thing or just for
the
static protection and then a separate heavy conductor to provide the shack
equipment earth.
In either case how can I ensure that the earthing does not radiate RF (I
assume
that making sure the aerials are correctly balanced with suitable baluns
fitted is
the answer here.)
I did here about using RG8 type coax and connecting both inner and screen
to the hardware in the ground but only connecting the shack earth buss to
the
inner - any thoughts on this.

Cheers Martin

------><------- snipped

Oops I forgot to add :-
REMOVE _NOSPAM_ to send email back to me or reply to the group.

Thanks Martin

Quote:> Hi, and thank you for reading this.
> I am in stalling my radio station in to the small "box room" on the 2nd
> floor
> of the building and I have in the past not worried about a separate earth
> for
> the station. But as this station is going to be a more permanent
arrangement
> than my other previous locations I want to make sure that :-
> 1) the station is safe electrically. (of course the supply earth will be
> connected)

Steve

Quote:> Hi, and thank you for reading this.
> I am in stalling my radio station in to the small "box room" on the 2nd
> floor
> of the building and I have in the past not worried about a separate earth
> for
> the station. But as this station is going to be a more permanent
arrangement
> than my other previous locations I want to make sure that :-
> 1) the station is safe electrically. (of course the supply earth will be
> connected)

If not, under certain fault conditions a LOT of currrent can try to pass via
your shack to earth. Not good.

Quote:> 2) protected form static (lightening etc).

You can get devices to protect against lightning but having seen the effects
of lightning tests I don't think I would trust a cheap one. I always
disconnect.

Quote:> 3) has a good RF performance. (this means low resistance earth connection)
> 4) is as clear of EMC problems as possible.

For VHF/UHF  the problems are  generally resolved by using good coax,
connectors, sensible antenna siting, and filtering (as required).

For HF, given the likely problems of a earth lead impedance at HF, I
recommend an external ATU- either a SGC (or similar) automatic beast or a
remotely variable arrangement. The latter need not be overly complex- a
simple LC arrangement, L either switched with relays or a roller coaster
with a small motor (a cheap electric screwdriver is ideal) and a motorised
capacitor(s). I can look out a circuit I did for someone else if you like-
he want something cheap and cheerful and I think the motorisation cost him
about 10! I works very well, if I ever get around to HF myself I may build
one.

To get a good RF earth you can run out radials from the ATU, the more the
better. These should be bonded to an earth rod at the ATU.  A buried 'earth
mat' is nice but not always practical.

The above approach tends to keep the RF 'in' via the coax and equipment
casing until it get to the ATU which, as the latter is remote,  minimises
coupling to other equipment.

Once the RF gets to the antenna it may still cause EMC problems- but that is
down to the fact it is radiating, which it is meant to do ;-)  Then it is
down to filtering to minimise harmonics etc. and coupling into domestic
items.

73

Brian
G8OSN
www.g8osn.org.uk

Both Peter Chadwick and I, who've had previous discussions and agreement
on this would profoundly disagree with you!

PME, where the neutral has a disconnection somewhere outside of your
property has likelihood to pass huge amounts of current, and hence  a
rise in potential down and to any local earth you might provide or have
in your home. It is a cheap but dangerous way to supposedly provide an
electrical earth.

The answer is to provide yourself with some good quality ELCB's (30ma if
possible) at your shack and home. Provide yourself with a good quality
earthing system which is tested to current standards and when this is
done disconnect the crappy PME system.

And yes I have seen the effects of a disconnected neutral with PME,
which has resulted in persons receiving shocks as well as interference
to electrical equipment

 From someone with Experience! Who has his PME disconnected and that's
the way it's staying!

Quote:> Well is that so? Add yourself a bit of extra earthing and bond it to the
> PME - I think NOT!

> Both Peter Chadwick and I, who've had previous discussions and agreement
> on this would profoundly disagree with you!

Quote:

> PME, where the neutral has a disconnection somewhere outside of your
> property has likelihood to pass huge amounts of current, and hence  a
> rise in potential down and to any local earth you might provide or have
> in your home. It is a cheap but dangerous way to supposedly provide an
> electrical earth.

Quote:> The answer is to provide yourself with some good quality ELCB's (30ma if
> possible) at your shack and home. Provide yourself with a good quality
> earthing system which is tested to current standards and when this is
> done disconnect the crappy PME system.

 >

Quote:>  From someone with Experience! Who has his PME disconnected and that's
> the way it's staying!

Quote:> I did here about using RG8 type coax and connecting both inner and
> screen to the hardware in the ground but only connecting the shack
> earth buss to the
> inner - any thoughts on this.

> Cheers Martin

watch this space - if it moves, see your optician.

Quote:> Hi, and thank you for reading this.
> I am in stalling my radio station in to the small "box room" on the 2nd
> floor
> of the building and I have in the past not worried about a separate earth
> for
> the station. But as this station is going to be a more permanent
arrangement
> than my other previous locations I want to make sure that :-
> 1) the station is safe electrically. (of course the supply earth will be
> connected)
> 2) protected form static (lightening etc).
> 3) has a good RF performance. (this means low resistance earth connection)
> 4) is as clear of EMC problems as possible.

> So any one got some pointers or helpful hints on installing a separate
> station
> earth. The ground connection is easy 3 to 6 off 6' long 1" dia copper
pipes
> driven all the way in to the soil (I know it is a big is job but not
> impossible).
> The bit I am puzzling over is do I use a heavy copper strap as used on
> church
> lightening conductors to provide a common earth for every thing or just
for
> the
> static protection and then a separate heavy conductor to provide the shack
> equipment earth.
> In either case how can I ensure that the earthing does not radiate RF (I
> assume
> that making sure the aerials are correctly balanced with suitable baluns
> fitted is
> the answer here.)
> I did here about using RG8 type coax and connecting both inner and screen
> to the hardware in the ground but only connecting the shack earth buss to
> the
> inner - any thoughts on this.

> Cheers Martin

Has anyone ever installed a mains isolating transformer or two
and run the shack items off of that ?  The idea being that those
shack items can then have their chassis connected to an 'RF'
garden-style earth rather than the household mains earth - there
being no direct connection between the two earths.

Cheers,

Gareth.

--
http://www.rat.org.uk/

Quote:> Just a thought.

> Has anyone ever installed a mains isolating transformer or two
> and run the shack items off of that ?  The idea being that those
> shack items can then have their chassis connected to an 'RF'
> garden-style earth rather than the household mains earth - there
> being no direct connection between the two earths.

73

Brian

I do this for my battery charger (a laboratory grade linear power
supply) and run off batteries.  However, I still connect the two
grounds together, at the ground rod.

I am not particularly bothered with the prospects of lightning, not in
the Pacific Northwest (we have the lowest incidence of lightning
strike in the 48 states).  However, I do still maintain lightning safe
practices like a one point entry window for all RF and electronics
which is tied to that same ground rod (less than 10' away).

Having an isolation transformer can be turned into an illusion of
isolation very easily through the casual connection of one piece of
equipment that has a ground path (somewhere).  Do you have an outboard
DSP that uses a "brick" power supply?  Ground may be busted DC-wise,
and yet it may be a conduit for noise from the Mains.  How about a
computer connection for packet?  Does the computer have a modem
attached to a phone line?  How about one of those premium SWR meters
with backlights and digital displays - again, plugged into some
anonymous wall-wart power supply?  The opportunity to violate the
isolation is exceedingly easy to come by and simple to implement.  

Another point, the isolation transformer is good at decoupling of RF
and noise, but it is not an RF ground buster.  You do not separate the
two grounds, except by the DC and low AC path.  At HF, it is a must
that you have two good grounds otherwise the transformer turns into a
very large coupling cap.  By the nature of good transformer
construction (which includes a Faraday shield), both grounds are
figuratively strapped together for RF.  The greater virtue of an
isolation transformer is it allows you to extend the "balanced"
metaphor where it counts: at the source.  It also lets you choose
which ground as being superior for your situation.

73's
Richard Clark, KB7QHC

Quote:> Would somebody please explain what a PME is. While you are at it, define
> ELCB.

Back in the good old days, the supply companies provided 3 conductors: Live,
Neutral and Earth.

For some reason (probably cost?) they did away with the need for a separate
Earth conductor by bonding Neutral and Earth together at the substation. The
buried cable used to bring the supply to homes has 'gaps' in the insulation
along its length, effectively connecting Neutral back to 'mother earth' at
these points. Since there are many of these along the length of the cable,
we get the term 'multiple earthing'. Only when the supply reaches your house
does Neutral get split from Earth again....

PME is a problem for radio amateurs because they may connect additional
metalwork in the ground to their Earth systems. (And because of PME they are
effectively connecting it to Neutral too....) If a fault in the buried cable
develops that breaks the outer Neutral/Earth connection, but leaves the live
intact then all the current supplied after the break will have to find
another way back to the substation through the ground...  If your earth
system is connected to the (now disconnected) Neutral conductor then hey
presto a fairly low impedance path is available... Your supply (and all your
neighbours downstream of the fault!) can now complete its circuit through
YOUR earth system. That's a heck of a lot of current (= fires and
explosions!)...

Another risk: Your earth has some resistance.... Voltage=Current x
Resistance.... So there will be a rise in potential around your earth
system. In other words it won't be at 'Earth' anymore... Which means that it
is a problem if you are, and you touch it...

So that's PME! It's late and I rambled... I wonder if *anyone* understands
me?

As for ELCB that's a bit easier. "Earth Leakage Circuit Breaker" - a device
that sits on a supply line and monitors the current in the Live and Neutral
lines. In theory these should be equal because all appliances etc. will form
a circuit between Live and Neutral. If the currents are not equal then some
of the live current is flowing elsewhere (to earth probably, hence an 'earth
leakage') - the ELCB detects this difference and shuts off the supply. Most
domestic ones trip at 30mA and reasonably quickly, the idea being that if it
is a person that the current is leaking through, they might live. In large
installations with lots of PC's and stuff the capacitors connected between
the supply and earth in the power supplies can have a cumulative effect,
leaking enough current to trip ELCB's - you can get special ones with a
higher trip rating for these kinds of situations.

Oops, I rambled again...

HTH (a bit!)

Dan.

You have come up with the clearest explanation of PME v radio earth that I
have ever read.
I have always wondered why a PME supply could fail so.
Now I know.

Many thanks

DE G6 KHP

Dave