With general purpose, multi-band antennas such as yours, taking one band
with another, the higher the feedline impedance the less the loss in the
feedline.

This is because feedline attenuation in dB is directly proportional to R/Zo
where R is the resistance of the feedline conductors and Zo is the line
impedance. This simple relationship applies from 50-ohm coax (or lower) up
to 600-ohm (or more) wide-spaced open-wire line.

Ordinary 50-ohm coax is fine ONLY when the input impedance of the antenna is
itself approximately 50 ohms purely resistive and the line length is not
very long. But with multi-band antennas Zin is most unlikely to be anywhere
near 50-ohms on any band. It is more likely, taking one band with another,
to be several hundred ohms or even 1000 ohms with a high reactance
component.

Assuming the conductor resistance to be of the same order for both coax and
balanced-pair lines of the same length, line loss will be appreciably less
for the higher impedance lines. In fact, for the physical sizes usually
involved, spaced balanced wires have a lower conductor resistance than
ordinary coax and this swings the use of spaced lines further in their
favour.

Even a 300-ohm twin line with substantial conductors, not the flimsy old TV
downlead type, will effect an improvement over the usual sort of coax.
450-ohm ladder line is most popular because of cheapness and relative ease
of installation. But for perfectionists, on very long lines, a 5" or 6"
spaced 600-ohm work-of-art cannot be bettered.

With low-loss, high-Zo lines SWR on the line can usually be forgotten about.
But a high SWR can make severe demands on the tuner however.

Transmission line Zo, of course, is unrelated to antenna efficiency which
with a high antenna is nearly always good enough to be considered 100%.
----
Reg, G4FGQ

Reg Edwards wrote:

Even a 300-ohm twin line with substantial conductors, not the flimsy old TV
downlead type, will effect an improvement over the usual sort of coax.
450-ohm ladder line is most popular because of cheapness and relative ease
of installation. But for perfectionists, on very long lines, a 5" or 6"
spaced 600-ohm work-of-art cannot be bettered.

any reason that silicon sealant would not be as good as anything else when
fixing (gluing) the wires to the slotted holes of the spacers in a homebrew
ladder line? Any reason why this same substance would not be appropriate to
seal up the ceramic tubes where such lines go through a wall?

this stuff is tough, weather resistant, sticks, and stays flexible.

Bill, K6TAJ

The electrical properties of sealing materials and greases are not defined
or specified. They probably make poor dielectrics when surrounding or are in
between transmission line conductors. I wouldn't use the stuff. A few
spots of super-glue would be ok.

There's no need to run open-wire line through walls and windows via two
spaced holes. The building material between the wires will probably be of
awful dielectric quality anyway.

Just bring the pair of insulated wires close together for a short distance
and run them through a single somewhat larger hole lined with a short, pvc
or polythene tube. Slope the tube and the line to prevent rainwater from
running indoors.

When coming through glass or DRY varnished timber a single hole is fine. On
high power lines make sure the insulation on the wires where they are close
together is thick enough to withstand the high voltage at high SWR.

At HF, the discontinuity in Zo due to bringing the wires close together for
a few inches, even a foot or more, is absolutely negligeable. And there's
nothing wrong with changing from a long open-wire line (outdoors) to a short
ladder line to the transmitter (indoors).

Use a simple choke balun between the transmitter end of balanced lines and
the tuner. The luxury of a balanced tuner is unnecessary.
----
Reg, G4FGQ

====================================
Reg Edwards wrote:

Even a 300-ohm twin line with substantial conductors, not the flimsy old
TV
downlead type, will effect an improvement over the usual sort of coax.
450-ohm ladder line is most popular because of cheapness and relative
ease
of installation. But for perfectionists, on very long lines, a 5" or 6"
spaced 600-ohm work-of-art cannot be bettered.

any reason that silicon sealant would not be as good as anything else when
fixing (gluing) the wires to the slotted holes of the spacers in a
homebrew
ladder line? Any reason why this same substance would not be appropriate
to
seal up the ceramic tubes where such lines go through a wall?

this stuff is tough, weather resistant, sticks, and stays flexible.

Bill, K6TAJ

It seems to me that the slightly larger single hole through my house wall up
near the peak (which is nothing more than an inch of wood really) is more
intrusive than two small spaced holes through which I could insert a 3-4" long
old style ceramic insulator tube. There would be a short run of 10 feet to a
spot in the ceiling (again nothing more than 1/2" of redwood) into which I
could use the same type of ceramic tube, after that it is only a couple more
feet to the rig. I do like your idea of angling the tube coming from outside to
counter the possible dripping in of moisture (rain), also will put what is
called a drip loop in the line before it enters the tubes so the wires are
aiming uphill at that point. I already have a balanced tuner on hand so I might
as well include the luxury since I have it. I will take your advice and avoid
these sealants and use a dab of super glue. In the end, if this line gives me
trouble (with the neighbors phones etc.) I will go to coax. But I do want to
give this old style balanced line a shot first since there seems to be a
handful of operators who do recommend it.


73 Bill K6TAJ

Reg Edwards wrote:

The electrical properties of sealing materials and greases are not defined
or specified. They probably make poor dielectrics when surrounding or are in
between transmission line conductors. I wouldn't use the stuff. A few
spots of super-glue would be ok.

There's no need to run open-wire line through walls and windows via two
spaced holes. The building material between the wires will probably be of
awful dielectric quality anyway.

Just bring the pair of insulated wires close together for a short distance
and run them through a single somewhat larger hole lined with a short, pvc
or polythene tube. Slope the tube and the line to prevent rainwater from
running indoors.

When coming through glass or DRY varnished timber a single hole is fine. On
high power lines make sure the insulation on the wires where they are close
together is thick enough to withstand the high voltage at high SWR.

At HF, the discontinuity in Zo due to bringing the wires close together for
a few inches, even a foot or more, is absolutely negligeable. And there's
nothing wrong with changing from a long open-wire line (outdoors) to a short
ladder line to the transmitter (indoors).

Use a simple choke balun between the transmitter end of balanced lines and
the tuner. The luxury of a balanced tuner is unnecessary.
----
Reg, G4FGQ

====================================
Reg Edwards wrote:

Even a 300-ohm twin line with substantial conductors, not the flimsy old
TV
downlead type, will effect an improvement over the usual sort of coax.
450-ohm ladder line is most popular because of cheapness and relative
ease
of installation. But for perfectionists, on very long lines, a 5" or 6"
spaced 600-ohm work-of-art cannot be bettered.

any reason that silicon sealant would not be as good as anything else when
fixing (gluing) the wires to the slotted holes of the spacers in a
homebrew
ladder line? Any reason why this same substance would not be appropriate
to
seal up the ceramic tubes where such lines go through a wall?

this stuff is tough, weather resistant, sticks, and stays flexible.

Bill, K6TAJ

Jeez Reggie,

On Mon, 26 Apr 2004 09:21:12 +0000 (UTC), "Reg Edwards"
wrote:

The electrical properties of sealing materials and greases are not defined
or specified.
However...
A few spots of super-glue would be ok.

I would be MOST curious about the defined properties of this wondrous
material. However, super-glue is not a void filler a function which
may still need to be performed.

Bet let us continue.

There's no need to run open-wire line through walls and windows via two
spaced holes. The building material between the wires will probably be of
awful dielectric quality anyway.

seems to contradict:

When coming through glass or DRY varnished timber a single hole is fine. On
high power lines make sure the insulation on the wires where they are close
together is thick enough to withstand the high voltage at high SWR.

Which in turn seems to lead to another contradiction:

At HF, the discontinuity in Zo due to bringing the wires close together for
a few inches, even a foot or more, is absolutely negligeable.

Hmm, just about spark gap dimensioning, close to combustibles, High
SWR jacked up even higher to boost voltage nodes more (I don't know
how the "short" distance ameliorates this - must be in the actuarial
tables somewhere).

This was certainly the most obscure way of saying don't worry about
it. ;-)

73's
Richard Clark, KB7QHC