> On Aug 4, 2016, at 1:40 PM, Jim Brown <jim@audiosystemsgroup.com> wrote:
You're asking the right questions, Paul. And balance is determined by the
entire antenna system, not only the feedline and the transmitter (tuner). Most
REAL antennas are unbalanced by their surroundings, and most REAL parallel-wire
feedlines are unbalanced by their surroundings -- we have to get them through
walls, for example.
When I bought my FT-950 4+ years ago I bought it with an Astron switching
supply. I wanted a lightweight “desktop” supply. I don’t remember what kind of
noises I heard from it, nor the exact spacing, but whatever I did hear, maybe
every 50 KHz, it sure was annoying. (At the time, I didn’t know it was the
power supply that created the noise.) I phoned the dealer who sold it all to
me. “What kind of transmission line are you using?” he asked. (I was surprised
at the seemingly irrelevant question, and hesitated.) “450-ohm window line,”
was my reply. He then said, “You need a linear power supply." I sent back the
switcher and got an Astron RS-35M (that weighs a ton) and have had no noise.
No way is my 140’ inverted-V balanced, and I knew this; as far as I know, it’s
“unbalanceable." The apex is at 33’, and each leg is over different terrain
that is of different heights. One leg now even goes through extended branches
of a tree! (I can’t stop it from growing.) The antenna support pole is about 50
feet from the shack. The window line, with a few twists to it, drops straight
down for about 27’, then heads for the house, suspended above the lawn, also
with a number of twists. But there are a few splices along the way, and a dual
banana plug and jack quick-disconnect I devised.
The window line attaches to a Balun Designs 1171 current balun outside the
shack. From the balun an 8’ length of RG8 runs through the wall to the Palstar
transmatch. A balanced system? I don’t think so. Regardless, I’m pleased with
the antenna’s performance 80 - 10 and I have fun with it. Isn’t that the point?
Howard N7SO
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