On Feb 1, 12:09 pm, "Tom" wrote:
On Jan 30, 9:07 pm, wrote:



Back in Nov 2005 there was a thread comparing coax withbalanced
feedlines.

At that time I held the viewpoint that coax was "better" thenbalanced
feedlines
for almost every receiving application.

In the last few months I have been experimenting with antennas other
then the
common "long" wireantennafed to coax with a 9:1 transformer.

Forbalancedantennas like active dipoles, significant reduction in
noise engress
can be obtained withbalancedover coax if a true balan is used at the
typical
unbalanced HFantennainput. I have noted significant reduction in
common mode,
requiring much less ferrite, withbalancedversus coax.

For the "long" wireantennawith a 9:1 I have not found a suitable
wiring scheme
forbalancedto work better then coax.

Care must be taken in constuction to insure as much physical symetry
in the active
dipole as well as the balun at the receiver end.

While I am not a fan of loops, I suspect that with proper attention to
construction
and wiring, loops to could benefit frombalancedfeedlines. Acitve
loops will require
great attention to the power/RF combiner to insure that no un-balance
is added.From my limited experience, active loops are not a good choice for

balanced
for this reason.

In direct comparsions an actve dipole outperformed an ALA 1530 and a
WL1030.
So except for my ancient MaKay Dymek DA5, which I keep for sentimental
not
practical reasons, I have decided to not investigate loops any
further.

Single ended active antennas and other unbalanced antennas will, in
general,
be better with coax instead ofbalanced.

When the weather moderates I intend to compare some special "tightly
twisted"
audio cable with plain zip cord.

Terry

I've been thinking of making a triple dipole fed by three pairs of a
CAT5 or CAT6 cable with a switcher at the receiver(s) to select any
one, any pair or all three, with phase reversals on each, feeding a
balanced/unbalanced antenna tuner. The three dipoles would be
electrically short, concentric, mutually orthogonal - one horizontal
and two as an X in the vertical plane. Might provide some directional
and polarisation selectivity. Mounted high and away (with short
elements it is easily away compared to a 1/2 wave dipole), it gets
away from the residential noise and interference sources and the
balance should be fair.

Attenuation may be excessive - here's Belden's 1300A for outdoor use:

MHz - dB/100 m
1 2.0
4 4.1
8 5.8
10 6.5 (vs 3-5 dB for RG-59/58)
16 8.2
20 9.3
25 10.4
31.25 11.7

Might have to go to an open wire line.

Check out this dp5t balanced switcher:http://cgi.ebay.com/
_W0QQitemZ280068890746

Tom

I compared "standard", no name, zip cord and radio shack 18G speaker
wire
and compared both to a variety of coax cables. One antenna was sightly
over
130' away. No significant difference was noted between the cables. I
say
"significant" because it always took a few minutes to change feedlines
and
band conditions were always in flux. the main difference was that for
balanced
antennas the zip cord or speaker cable had significantly lower QRM
from "local"
man made noise sources.

Zip cord is cheap enough to not break anyones piggy bank and if it
doesn't
work it should not be a big deal.

I only posted this because in 2005 I was very insistant that coax was
always the
best choice. 30 years of professional work in electronics, and the ~15
years I
had spent as a SWL befroe that had convinced me of somehting that I
now think
differently. My comments about balanced being better only applies for
balanced
antennas. While I have confidence in my measurement and the accuracy,
I
still have some doubts. In part due to 40 plus years of using coax.

The more turns per inch equals more loss and the loss increases faster
with frequency
for "very" twisted cables. I think anything more then a few turns per
foot will not
help noise pickup but will increase attenuation.

All I can say is to try it and see how it works for you,

Terry