[1000mp] Groundsystem and RFI-problems with FT-1000MP

[1000mp@mailman.qth.net]

Dear John (Morris and others),

> Please explain what the term "double pulse" (ground) means.

Language problem!

I mean: "double ground rod". We used two ground rods in an angle of about 90
degrees. One ground rod in an angle of about 45 degrees to the house and one
rod in an angle of about 45 degrees from the house. Both rods are tight
together and are connected to the antenna mast.

> If the antenna/shack ground system is separated from the houses electrical
> ground, won't a lightning hit to your antenna result in a very large
voltage
> difference between the equipment ground and the AC input?  (start a fire?)
> In the U.S., when the antenna and AC grounds are tied together well, the
AC
> line voltage rises with the ground voltage rise due to the center tap of
the
> AC transformer being tied to the ground.  This reduces the amount ofarcing
> that would occur.  Perhaps lightning is not a big problem there as it is
> here, sometimes even in the Winter.  (Or maybe I'm am not understanding
> something!)

Very interesting!

I quote the ARRL handbook for radio amateurs 2000, page 28.7 'GROUNDS':

...Many amateur stations have several grounds: a safety ground that is part
of the ac-wiring system, another at the antenna for lightning protection and
perhaps another at the station for EMI control. These grounds can interact
with each other in ways that are difficult to predict.

Ground Loops
All of these station grounds can form a large ground loop. This loop can act
as a large loop antenna, with increased susceptibility to lighting or EMI
problems...

ARRL handbook for radio amateurs 2000, page 22.2 'THE STATION GROUND':

...The second job the ground system must perform is to provide a
low-impadance path to ground for any stray RF current inside the station.
Stray RF can cause equipment to malfunction and contributes to RFI problems.
This low-impedance path is usually called RF ground. In most stations, dc
ground and RF ground are provided by the same system....

ARRL handbook for radio amateurs 2000, page 9.7 'GROUNDS':

...Some think that RF grounds should be isolated from the safety ground
system - that is not true! All grounds, including safety, RF, lightning
protection and commercial communications, must be bonded together in order
to protect life and property...

Unquote

The text on page 9.7 is equal to what you wrote.

However; I am not able to bond my RF-groundsystem together to the ac-wiring
groundsystem! Oh yes I can; in my shack, but does this make sense? I use an
'EXTREME ISOLATION TRANSFORMER' to "seperate" the ac-wiring of our house
from the equipment in the shack.

Please your advise (it is not my intention to be pigheaded).

We had two direct lightning strikes sofar, without any damage to the radio
equipment. But this does not mean that it is not necessary to improve the
groundsystem in the way you describe it.

Thanks and 73!
Hans.

Ham Radio:
PA1HR

Sites:
www.remeeus.nl
www.qsl.net/pa1hr

e-mail:
hans@remeeus.nl