This is excellent. I've believed for many years that most amateur ground
system present more of a hazard to equipment than a help. Manufacture's
manuals all recommend a "good ground" however but this could be just a CYA
thing. Connecting the tower and coax shield grounds to your power line
ground isn't often easy and is seldom done. My Electrical entrance is
grounded to one old, beatup looking piece of conduit driven outside many
years ago and it's effectiveness is questionable. Running a large wire
between the coax of my dipole and that ground rod would be very difficult
and very long.
One thing I've done over the years is to use a large knife switch to
disconnect and ground my antennas when I've not on the air. The station
ground is not connected to the rig at all and the antenna ground rods are
used only to ground the antenna when I'm away. Somehow I got the idea that
having that big wire over the house, connected to ground acts as a constant
path for static buildup and may even help protect the house.
Having 2 ground systems, one for the electrical and one for the rig is
really asking for trouble and I suppose the interconnecting wire is the
cure. I'm going to revisit this in my shack and see if it can be done.
Steve N4LQ
----- Original Message -----
From: "Robert & Linda McGraw K4TAX" <RMcGraw@Blomand.Net>
To: <tentec@contesting.com>
Sent: Wednesday, June 16, 2004 7:32 PM
Subject: [TenTec] On Grounding
>
> This message started with other Tentec subject lines but due to the
subject
> matter and the fact it's summer (thunderstorm season) here in the US, I
> thought I'd pass along a few ideas and facts and try to dispel some
> incorrect notions regarding grounding.
>
> Today most ham stations do not need a RF ground. Shocking to read isn't
it!
> Well it's true. Ask, does your antenna system require a ground to
operate?
> If you use a vertical, an inverted L or a long wire or a sloper or other
> unbalanced configuration then with out question your antenna does require
a
> ground to operate satisfactorly. On the other hand, if you use a coax fed
> beam, a coax fed dipole, a balanced fed loop or a balanced fed dipole
> (resonant or non-resonate) then the antenna system does not need a ground.
> Any of these will work just fine even in outer space and certainly there
is
> no place to drive a ground rod there. Oh my!
>
> Then why do we jump through hoops to put in a ground system? Simple,
> lightning protection. On this topic, one thing to remember is the fact
that
> all driven grounds must be bonded together in order to be effective during
a
> nearby lightning strike. The NEC electrical code requires it. And it
isn't
> safe if its not done. That means the tower ground, the TV antenna ground,
> the telephone ground, the well pump and anything else that could be
> considered as needing ground for lightning protection. And of course the
> lightning rods on the house. You do have them don't you? Or is your
tower
> the lightning rod? None of these items actually require any form of RF
> ground.
>
> Now we must decide do we need a RF ground or a lightning ground. We
> generally believe that we must connect everything together in all sorts of
> helter skelter ways and schemes producing multiple paths for current
flows.
> In days gone by, transmitters and antennas did require a RF ground to
> operate satisfactorily but their output circuits were vastly different
from
> todays radios. Today, the most effective method is to connect a
reasonably
> large, low resistance, low inductance wire from one piece of station
> equipment to another. In the simplest terms, tuner ground connected to
> amplifier ground, amplifier ground conected to tranceiver ground and
> tranceiver ground connected to the power supply ground. At this point
then
> where is ground connected? For safety reasons and according to the NEC,
the
> 3rd pin of the AC line completes the requuirements. I use #10 AWG
stranded
> with #30 wire marine cable and apply crimp on connectors and then solder
the
> connectors too. This makes for a very low R connection, yet it's very
> flexable and easy to work with and move equipment around as needed.
>
> For lightning protection all feedlines, being coax or balanced, all rotor
> lines and remote antenna switching control lines should be protected by an
> approprate device (I'll not mention brands) at the point they enter the
> building. The antenna supporting structure must be grounded at its base
and
> this ground must be connected to the AC mains ground by some hard bonding
> technique. Failure to do this will (repeat WILL) produce a step voltage
> between the two during a nearby lightning strike. The result is that
> current will flow between the two and usually the radio equipment is in
the
> current path and is the first to smoke.
>
> If you have applied an external ground to eliminate TVI, BCI or telephone
> interference then the topic of discussion should turn another direction.
In
> most cases there's problems with the relationship between the antenna and
> the device being offended with. (pardon the grammar)
>
> In most cases we go overboard to provide what we believe to be a good
ground
> system when indeed it is not needed and worse, it is often applied
> incorrectly.
>
> I will directly respond to all e-mail questions if you would like more
> dialogue on the topic.
>
> 73
> Bob, K4TAX
>
>
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>
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