In article . 196,
"Ed_G" wrote:

"Left Floating" so that there is less Capacitance to RF Ground, and
more distance between the vertical parallel Feedlines. It would even
help if you can use twin Coax Runs, to put them on opposite sides of
the Aluminum Mast, which would give you more separation with the same
Coupling Capacitance to the Mast. Capacitive coupling to RF Ground,
is the Killer here, and you MUST reduce that, as much as possible,
if your system is going to have any chance at reasonable operation.



Please read my response and question just posted to Owen. With both
shields tied together, but not grounded, nor connected to the antenna
either, I do not understand how common mode current is an issue on the
shields.

We could use the mast as a physical separation as you suggested, (
the mast is not grounded, either, but again, what is the point, if the
two coax shields were "as one" anyway?


Ed
I

Most of the discussion here is more esoteric, than practical. You have
an imposed Antenna Requirement, that gives you little wiggle room in
what you can do. I have given you the ideas, that are proven in the
Real World, for installations with similar requirements. As I stated
in my first post, these type systems, ALL preform equally BAD, when
compared to the Antenna Systems, that these type tuners were DESIGNED
to feed. They are intended to feed a Marconi Vertical, with a very
Low Impedance RF Ground. That is where they work BEST. Everything else
will be a poorer situation. How poor, will depend on a BIG pile of
variables, most of which are esoteric in significance, and will
not make a significant difference in actual Practical Performance of the
Station. Again as I stated in my last post, Capitative Coupling to
RF Ground is the BIG Killer, the second largest problem is selecting
antenna length, so as the Natural Impedance of the antenna is NOT
anywhere near a frequency that you need to operate on. All the rest,
is Picking Nits, and can be discussed at infinitum, without changing
the actual performance in any significant way. One of the posters
suggested building an "counterpoise", (God, I hate that Term) RF Ground
from Aluminum Alarm Tape, on the roof, and then feeding what would be
essentially a end feed wire antenna. That would be preferable, IF you
could get the Biggies to go along, but that was NOT, part of the
original Problem. In the real WORLD, your Comm's are going to depend
more on, if the Band is Open, for your Distance, and Frequency, to
the destination, than the Antenna design, and if the Band is NOT open,
you aren't going to talk, as Ground Wave Comm's are not usually a
significant part of HF Communications.

Just a note, for historical purposes. There was a highly modified
SEA1612B Tuner that was designed to feed a Balanced Antenna. It was
fabricated out of Two, (2) Tuner Boards, using a Common CPU/Sensor
System, that determined the configuration of the Switched Elements
on one side of the Antenna, and then locked the same configuration
on the Second board for the other side. This scheme was developed
by Don Hollingsworth Sr. at G&L Marine Radio, in Seattle, Washington,
and was deployed in one or two installations of Maritime Mobile Limited
Coast Stations. I never did hear just how well they worked.

--
Bruce in alaska
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