On Mon, 27 Feb 2006 14:29:47 GMT, chuck wrote:

One more way to word the question: if you tie the open-wire lines
together at the tuner/transmitter and feed the antenna as a vertical,
all of the current in the line will be common-mode. Would that be less
likely to cause undesirable coupling than the exact same antenna with
transmission line unbalance.

Hi Chuck,

When you tie them together, you have to be referencing that "common"
lead to something. Usually that something is ground. Common Mode
current springs into existence by definition.

Where did ground come into the picture? Usually through the power
supply. The power supply gets it from the mains, and thus you see the
origin of getting RF into the house.

I wrote earlier about how a religious devotion to balancing an
antenna/feed can be easily disturbed when you connect your line to the
rig. The rig has a ground connection even if you didn't drive a
ground rod specifically for it, nor purposely establish a ground path.

Some might think that their tuner isolates their twin line feed from
ground. I seriously doubt that is true. Most tuners I've seen use a
voltage BalUn which design violates that form of isolation, or turns
the core into a heating element, or both. Even link tuners have the
prospects of not having a truly balanced connection. I would say the
prospects are much better, as the designers were working toward that
goal, but it is not always achieved.

73's
Richard Clark, KB7QHC