jawod wrote:

If we assume that there is a well matched antenna: twin line to balun,

SWR does not cause ground currents or RFI.

coax to transceiver. My RF concern was that a long line to ground would
serve as an antenna to bring RF into shack. If this is not the case, or
if this is easily dealt with, great.

A long line to the ground definitely WILL act like an antenna, but the
effect is absolutely unavoidable.

If you look up national electrical codes you'll see external wires or
cable grounds entering a dwelling are supposed to be bonded or grounded
to the same ground as the power mains and other utilities. This is
primarily to ensure if there is any type of ground fault or surge (i.e.
lightning) everything in the house rises at the same rate. You don't
want ANY surge current flowing through the house wiring, and bonding
grounds outside the house greatly reduces currents through the house.
This is called a "common point ground", and it REDUCES ground loops.

Second, amateur gear is not normally UL/CSA approved. It sometimes
contains high voltage. High voltage inside a metal box can be a
problem. If you get a short from a transformer primary to secondary the
case can actually rise to the full amount of high voltage. That voltage
can appear on antenna cables (as it can if other components inside the
box fail), or between that device and other devices. While not all
amateur stations have HV devices, most have line operated equipment. It
is possible to have 120VAC appear on cabinets and cables in those
devices. Because of this, we should always have an independent safety
electrical ground. That ground is required by code to be bonded to the
service ground.

That leaves us RF. There are only two things required for RF in the
shack prevention.

The first is you use an antenna with a two conductor feedline. It can
be coax or twinlead. The antenna system can have ANY SWR, but it must
ensure the currents on each conductor of the coax or twinlead are
perfectly balanced and 180 degrees out of phase.

http://www.w8ji.com/verticals_and_baluns.htm

If the currents are not balanced, some current will flow back to the
power lines, telephone lines, and other connections to the station
equipment. The cure for this is really fixing the antenna system.
Although a "RF ground" in the station can cover up the problem, the
feedline will still radiate and receive signals.

The second is your station must have a common "ground buss" and all
equipment in your station should be bonded to that ground buss. The
importance of an external low impedance RF ground on that ground buss
is actually very minor. The real importance is that ALL equipment in
the shack operate at the same RF potential. In second floor locations I
actually laid aluminum foil under carpet for my shack RF ground, the
large "plate" acting like a groundplane for RF, but I ALWAYS had an
external safety ground. That's because I always ran amplifiers and
other equipment that was not UL/CSA listed. Sometimes you just do what
you have to do to get on the air.

It's best if you work out any RF problems IF they occur. If it was me,
I would not worry about RF problems until they showed. Safety is
another issue. If you are dead or the house burns down, it is too late
to work on problems.

The mains box is on the opposite side of the house...that ground is not
conveniently located.

What you do is up to you. I'm only telling you what the NEC tells us we
should do and why. It does NOT mean your insurance will be invalid if
you don't follow NEC, it only means they can cancel you. State laws
require insurance companies honor policies, but if they find out
something isn't safe they can cancel you. Otherwise they can only
refuse to pay for fraud or an intentional violation of the agreement
you signed.

You station is less safe for lightning and for electrical safety if you
don't bond the grounds, but I have had many stations over my lifetime
that did not follow that guideline. That's what you should do, and you
should do it for electrical and lightning safety.

My coax will go thru a lightening arrestor (Polyphase) which will be
earth grounded. If I run a low gauge wire from that earth ground to the
main box ground, then this is prevents ground loop? What if the
distance to the mains box is 60 feet?

Yes. It reduces chances of harmful ground loops. I believe you should
find that on polyphasers site in technical papers.

Try:

http://www.polyphaser.com/ppc_TD1016.aspx

and other technical papers.


73 Tom

jawod wrote:


Reading the two responses so far...I'll get my advice elsewhere. Typical
internet group response...mildly insulting and of no direct value. I
first have to know what ground means? Whatever.
Imaginary numbers apparently require imaginary minds.

Richard wrote a very detailed response which covered pretty much
everything you need. Perhaps you did not read it all.

What didn't you understand?

If you didn't understand something, you should have asked about what you
did not, and he would gladly (I'm assuming, but I'm pretty sure on this)
have answered your question.

tom
K0TAR