[Antennas] How important is the ground?

[Jack Painter]

Mike, we chatted about this off list.  But there were two seprate issues
there; ac mains grounding, and the possible benefit of grounding a battery
charger operation. On the first issue, it's black and white, the only path
for ground to maintain electrical safety is via the AC neutral and third
wire (ground), which are by the way bonded at the service panel.

On the charger issue, that's open to debate. But I think a short circuit in
a double insulated two-pronged battery charger would only be safely cleared
by the neutral wiring of the home, not a separate path to house ground from
the secondary side of the charger's transformer. That's just my opinion, but
I never heard of a battery charger fault that shorted dangerous voltage
across the secondary side if the transformer and rectifier, before it would
have had its fault cleared via the intended path of hot and neutral wiring.

Best regards,

Jack
Va Beach

>
> Jack,
>    The way I read David's message, he clearly states that the ground goes
> back to the "same" ground as the electrical system.  Since most 12V radios
> do not have a 3 prong outlet connected to them, it is prudent to
> connect the
> case to the electrical ground in some other fashion.
>
>    You also miss the point of an RF ground.  Yes, for safety, it must be
> bonded to the main electrical ground.  However, for a good RF ground, you
> need a short low impedance path, which most electrical grounds
> are not.  At
> my station, a copper plate is the main ground "point" close to
> the station.
> It is bonded with #6 back to the water main where the rest of the
> electrical
> system connects.  However, there are additional ground rods and
> connections
> running radially from that plate outside in a number of directions,
> including the antenna towers.  Ground connections must be considered
> "systems" and all must be bonded for electrical safety.
>
>    At field day, each station gets a ground rod as close to the rig as
> possible connected to it with flat braid or an old piece of coax.  All of
> the stations rods are then bonded to the rod at the generator
> with #6 solid.
>
>    I learned the hard way what an RF ground means.  Have you ever been
> "burned" by RF from touching the case of a transmitter that did not have a
> "low impedance" ground?
>
> Mike, W1NR
>
> -----Original Message-----
> From: antennas-bounces at mailman.qth.net
> [mailto:antennas-bounces at mailman.qth.net] On Behalf Of Jack Painter
> Sent: Saturday, May 21, 2005 2:18 PM
> To: antennas at mailman.qth.net
> Subject: RE: [Antennas] How important is the ground?
>
>
>
> David wrote:
>
> There are 4 different purposes for a ground connection to a radio.
>
> 1. electrical safety.  This only applies if you are connected to a power
> source that may seek to get to ground through the radio.  i.e. a
> commercial
> AC main, or a generator that is properly grounded.  If you run a
> charger on
> the battery while you are in the house you should have a ground connection
> that ties the rig case back to the same ground as the electrical
> system for
> your safety.
>
> --
> That's just not correct, David. It's advice so old that it goes back to
> before there was a fault-clearing design of all modern circuit breakers.
> Since that time, it has been counterproductive to ground the case of any
> three prong AC powered electronic device. In fact in the case of
> separately
> grounded radio stations as many of us have, the NEC and NFPA required bond
> from the radio station single point ground to the home's AC service main
> ground is the ONLY thing that will save your life.
>
> Ground rods do NOT, EVER protect your life in the event of
> equipment faults.
> Earth's impedance is far too high to protect from electric shock,
> and there
> is no way that using earth as a return circuit to the circuit breaker will
> ever clear a fault.
>
> Best regards,
>
> Jack
> Va Beach
>
> ______________________________________________________________
> Antennas mailing list
> Home: http://mailman.qth.net/mailman/listinfo/antennas
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Antennas at mailman.qth.net
>