I agree with Billy. Done properly, the safest and best approach is to ground
all station equipment to a single copper plate or bar, which is in turn
connected via a short, low-impedance path to a ground rod. All other service
grounds (A/C, telco, cable, etc.) should be bonded to this ground as well.
Further, a proper ground system should be installed at the tower, with
multiple ground rods connected via radials (I use 12 rods on my main tower.)
It's best to Cadweld all ground rod connections. Suitable lightning
suppressors should be installed on every conductor at both the tower and
house/shack (i.e., two suppressors per conductor, one at the tower end and
one at the shack end.) Surge suppressors should be installed on every
conductor entering the house, including A/C (special surge-suppressing
circuit breakers are made for this purpose), telco (their more modern
service panels have good suppressors, but the old one's don't), cable TV,
satellite, etc.
Some would counsel that you should unplug and disconnect all your ham gear
when a lightning storm is in the area. Fine, go ahead and do that, but in
complex stations and homes with lots of electronics and communications
services, it's best to install a proper ground/suppression system, ala the
above description, in addition. That's because there are too many wires to
disconnect and eventually you will miss one or more.
My fairly-complex computer-driven SO2R contesting station is setup this way
and I've never had a problem with lightning (knock on wood), ground loops,
RF grounding, hum, etc., unless I wired a cable incorrectly, failed to use
isolation transformers on audio lines, or failed to connect the chassis of a
piece of equipment to the ground system. In my opinion, that's exactly how
things should work.
If you have ground loops, you have not designed/installed your ground system
correctly, have not understood how your equipment is designed (e.g., audio
circuits), or you have very poorly conducting soil (e.g., you live at the
top of a rocky mountain.) In most cases, designing and installing a proper
ground system and connecting equipment properly is the answer. In rare
cases, you may have to use ground radials or counterpoises, but this would
be the exception to the rule.
If you have trouble with "RF Grounding", I suggest you take a look at your
antenna system. It's probably not designed/installed properly, either. For
example, balanced antennas require a balun to keep RF currents from
traveling down the coax shield and radiating -- destroying the antenna
pattern and/or causing havoc in the shack. If you install an HF antenna over
your roof, you're asking for trouble (been there, done that.) It's almost
impossible to keep RF out of the house wiring, especially if you run high
power. No amount of fooling around with "RF Grounding" or counterpoises will
solve that problem -- if you have a piece of house wiring that's resonant at
the antenna's radiating frequency, it's going to conduct RF into all of your
household appliances. About the best you can do in this case is add chokes
to the AC wires and shield the cabinets, and even that's likely to be a
losing proposition. Bottom line, get the antenna as far away from the house
as you can (my nearest antenna is 150 feet away and I have no RFI problems.)
73, Dick WC1M
> -----Original Message-----
> From: Billy Cox [mailto:aa4nu@ix.netcom.com]
> Sent: Monday, December 13, 2004 8:11 PM
> To: orion@contesting.com
> Subject: Re: [Orion] Orion - Work in Progress - Part 1 -WHOA!
>
>
> N0KHQ provides many interesting tips ... to make the new Ten
> Tec gear be less "RFI sensitive" ... most of which is worthy
> of consideration until:
>
> >Some hams get a little confused when talking about Grounding
> for RF and
> >Grounding for Lightning protection. They are not the same
> and should be
> >addressed separately. Grounding for Lightning protection
> will do very
> >little or RF grounding. But Grounding for RF will help with
> Lightning
> >protection.
> >
> >Most ham radio books illustrate a typical station grounding system,
> >where you have this big copper plate or bar behind your station and
> >every piece of your equipment is supposed to be grounded to this bar
> >and then a wire runs from this bar outdoors to a grounding rod. This
> >illustration is 100% totally wrong and does result in the biggest
> >ground loop in the history of Amateur Radio.
>
> Really? Didn't you post similar before and got challenged on
> this topic for posting advice that might lead to others being
> exposed to real damage?
>
> Gee, guess the pros have it all wrong then?
>
> Check the Polyphaser site and others for accurate
> descriptions as to how to create a SPG <single point ground>.
> For example, you need to tie in your telephone lines, and
> CATV, etc. for complete protection and no sneek paths ... and
> ... use the right size conductors for the site.
>
> I would strongly suggest NOT ignoring local codes and such
> ... unless N0KHQ is willing to personally replace anyone's
> gear that gets damaged from doing things as he has described
> ... lots of his text is OK, but not the paragraphs above.
> Here's the bottom line, it's your gear lost, not his,
> especially if you live in a area with frequent lightning
> damage issues.
>
> I would suggest everyone conducting their own due diligence
> and see what the pros do ... also you can check W8JI's posts
> on the other CQ-Contesting forums as to his advice too as to
> solid methods.
>
> Again, lots of useful info as to trying to keep the RF out of
> the newer Ten-Tec gear in his posts, but BE VERY CAREFUL as
> to exposing your gear and home to what might result in
> serious damage. .
>
> Season's Greetings to All,
>
> 73 Billy AA4NU
>
>
>
_______________________________________________
Orion mailing list
Orion@contesting.com
http://lists.contesting.com/mailman/listinfo/orion
|