RadioBanter - View Single Post - "Can twisted wire replace shielded wire?"

November 28th 05, 06:51 PM posted to rec.radio.shortwave

On 28 Nov 2005 08:59:00 -0800, wrote:

David wrote:
Try it with a true balanced input.
++++++++++++++++++++++++Ihave.
I used a home made 1:1 torroid tranformer with minitmal effects.
I even tried it with a 1:1 balun at the far end, with no effect.

The only point I am trying to make is that the twisted pair and
paralled
conductor that I tried were not completly balanced. Perhaps high
quality
CAT6 ethernet cable would be.

We are moving into the realm of "how many angels can dance on the
head of pin". Interesting from a philosphical point of view, but not
much
use in the real world.

I have been trying to find better ways to reduce noise since before
I got my EE. In my experience better reception, IE receiving the really

weak signals, has more to do with reducing the QRM and QRN then
"magic" feedlines. I am not in love with coax, it is just the
easiest/best
solution to keep my feedline from picking up noise, and with common
mode supression, keeping noise from finding it's way back up the shield

and getting into the antenna.

As I have said, if I lived in the woods, with no electrical equipment
to
be sources of RF noise, then the type feedline I used would not matter.

BTDT But in the world that I live in, there are a variety of noise
sources in
my house that I have mitigated as far as possible. One step in
mitigation
was to reduce QRM ingress as much as possible. With one, or more, PCs,
AC to DC power supplies, DSP(rather noisy) and other noise sources
in my shack, coupled with the other household equipment, "smart
furnace"
fridge, wifes PC, TV/VCR/DVD, microwave, alram clock, and every light
switch,
I found that I could not get a balanced RF feed to work.

However the audio that I distribute around our home is balanced for the

reasons you listed. At work we distribute some video via balanced
tiwn-ax
up to 2 miles. We are replacing these with fiber not because balanced
doesn't
work very well, but because lighting strikes keep frying the line
drivers.

In a situaiton where one was using a balanced antenna,like a dipole,
with
no significant local noise sources parallel, twisted or orpen ladder
line
would be great. For extremely high power transmit operations open
ladder line
is the best choice. But there will more leakage from the open line then
from coax.

Terry

Up until about 30 years ago, almost every radio station on the air was
feeding audio to their transmitters via unshielded wire phone lines.
No buzz.

Optoisolators as suicide devices.