Hi to all

When running a length of TX line through an environment where it is
susceptible to contact leaves or maybe branches, what is the best
choice.. window ladder line or coaxial wire?

In other words, will both of these type of lines have about the same
loss to natural environment objects or is one more sensible than the
other?

I am not talking about SWR losses or matched line losses.

Thanks de VE2PID

ve2pid wrote:
In other words, will both of these type of lines have about the same
loss to natural environment objects or is one more sensible than the
other?

If no common-mode currents exist on the coax, it will
be impervious to environmental losses. Under ideal
conditions, 100% of the energy fields are confined
inside the coax. That is not true for ladder-line whose
fields around the wires should be kept some distance
from environmental objects.
--
73, Cecil http://www.w5dxp.com

A very 'general' answer is that coax will have less 'variable' loss
from being near stuff than 'ladder-line' because of the way it's
constructed (and why it was originally made anyway). If that's the
only consideration you have to think about, then it's a fairly simple
question to answer. When you start thinking about the other
properties/characteristics of coax/ladder line, the answer isn't quite
so simple any more. (I like using ladder line, but I seriously doubt
if I try running it in a vehicle, see what I mean?)
- 'Doc


I've found that a 10ga loaded with small shot will clear out most
leaves that might interfere with ladder line. Large twigs, limbs,
etc, require larger shot. Gotta get that angle right though, that's
the hard part. Not to mention the neighbors...
(No, I'm really not that dumb. Just depends on how frustrated I am.)

wrote in message
...
A very 'general' answer is that coax will have less 'variable' loss
from being near stuff than 'ladder-line' because of the way it's
constructed (and why it was originally made anyway). If that's the
only consideration you have to think about, then it's a fairly simple
question to answer. When you start thinking about the other
properties/characteristics of coax/ladder line, the answer isn't quite
so simple any more. (I like using ladder line, but I seriously doubt
if I try running it in a vehicle, see what I mean?)
- 'Doc


I've found that a 10ga loaded with small shot will clear out most
leaves that might interfere with ladder line. Large twigs, limbs,
etc, require larger shot. Gotta get that angle right though, that's
the hard part. Not to mention the neighbors...
(No, I'm really not that dumb. Just depends on how frustrated I am.)


-------------


Twinlead/ladder line comes in handy for situations such as mine.

I'm running a Van Gordon All Bander dipole. Fed with 450 ohm twinlead, which
it is, I can tune virtually anywhere from 160 meters to 6 meters as long as
I'm tolerant of a bit of RF in the shack. To me, the versatility of being
able to transmit anywhere I'm legal from six meters down to 160 meters is
well worth the pattern changes and other characteristics of the
dipole/twinlead combination.

Just be aware that you can enter into situations with this setup that can
start a fire by arcing to an interior/exterior object if a kilowatt or more
is used. Maybe even less power, come to think of it. I set a curtain on fire
once this way. That was an interesting sounding transmission after I saw the
curtain ablaze.

For me, this setup works the best for my circumstances.

Feed this same antenna with coax and you'll run out of tuner swing long
before you'll match the same antenna to the same bands as matched with
twinlead. Chances are you'll also punch a hole through the coax' dielectric
insulator, which leads to breakdown (internal arcing) at even lower voltages
later on. Coax has its uses and I use plenty of it for the higher bands.
Just not on the low bands since I must make do with my single Van Gordon All
Bander antenna.

I apologize for not sounding as scholarly as many of you, but I'm getting
old and don't have time for that nonsense. 8)

Ed, NM2K

ve2pid wrote:
Hi to all

When running a length of TX line through an environment where it is
susceptible to contact leaves or maybe branches, what is the best
choice.. window ladder line or coaxial wire?

In other words, will both of these type of lines have about the same
loss to natural environment objects or is one more sensible than the
other?

I am not talking about SWR losses or matched line losses.

Thanks de VE2PID

The short answer is coax.

When properly balanced (that is, common mode current suppressed),
coaxial cable is totally insensitive to its electrical environment.
Ladder, window, and other types of twinlead line, however, are not.
They're most susceptible if the line has a high SWR and the contact with
water, other lossy material, or conductors occurs near a voltage peak,
but even when matched, considerable loss and/or impedance disturbances
can occur. There's very little good data on the effect of water, but I
made measurements of TV twinlead many years ago and found that it could
be lossier than even small coax when wet. Wes Stewart measured some
ladder line and found that it also could be quite lossy when wet. He
posted the results on this forum some years ago. While the loss
specifications of dry ladder line in an ideal environment are
attractive, it can easily become much lossier than coax when wet and in
close proximity to lossy materials such as leaves or damp wood.

Roy Lewallen, W7EL

On Jul 20, 9:54*pm, Roy Lewallen wrote:
While the loss
specifications of dry ladder line in an ideal environment are
attractive, it can easily become much lossier than coax when wet and in
close proximity to lossy materials such as leaves or damp wood.

Roy Lewallen, W7EL

I've got a UHF TV antenna that I use for 420 mhz ATV
reception. It's one of those corner reflector type deals
with a lot of elements.
In comparing 300 ohm twin lead vs 75 ohm coax, the
twin lead had the lowest loss when dry.
Or at least with the Belden "duo-shield" cable I was using.
But if it got wet, the twin lead loss was quite major.
I'd go from a clear picture to half snow..
I'd have to wait for it to slowly dry off to get my picture back.
I don't really use much ladder line as I prefer coax
for my everyday antennas.
But if I did, I would use a line with mostly air between
the conductors. Which means I'd probably make my own.
But the ladder line with the gaps in the plastic would
be better than twin lead.