Jim,

Well, let me say this...

I've run window line for years, and will be switching to open wire line, in
part, next year. In a test that I did about 7 years ago, I ran a 1 ft section
of window line across a metal flourescent light fixture, laying right on it. I
could measure no change in SWR and no change in signal strengths using a 40 m
horizontal loop on 40 m. I'd recommend running a test if possible and see if
it makes a difference.

Right now, I run an 80 m loop and run window line all the way to the tuner in
the shack. Only metal is about a foot away, water pipes and heating ducts that
parallel the feedline for about 25 feet. It works so if there is a problem,
it might not be severe and I'm willing to live with it, hi.

73s,

Evan

wrote:
Greetings
I have been using balanced line for many years and am convinced of its
virtues, particularly since I use a single tuned doublet for multiband
use.

The key to using balanced line is to know what impedance you are dealing
with looking into the feedline. If it's too high, baluns don't work. If
it's too low, tuners don't work. You can always measure the impedance
but I have found that EZNEC gives a close enough approximation to the
feedpoint impedance that you don't really need to measure it. Some of
the principles are explained on my web page under "No-Tuner All-HF-Band-
Antenna".
--
73, Cecil http://www.qsl.net/w5dxp

Jim,
with respect to keeping the system all balanced and running the balanced
line through portals along with metal objects,
you can simply make a length of shielded balanced line using two pieces of
coax with the braids connected at each end and connected to shack ground on
the inside end. It becomes a shielded balanced line of twice the coax Zo and
can be directly inserted into the transmission path with no problems.

Check out "Some Aspects of Series and Parallel Coaxial Cable Assemblies" at
Cebik's site, in particular the "Series-Connected Coax" section

http://www.cebik.com/spcoax.html

73,
John



wrote in message
oups.com...
Greetings
I have been using balanced line for many years and am convinced of its
virtues, particularly since I use a single tuned doublet for multiband
use.
The question I have never been able to get a clear answer on is this;
How critical is it for the balanced line to avoid metal objects?
Specifically, I now use about 6 feet of LMR 400 coax from a Radio Works
remote balun into my shack where I tune the antenna from either a
manual tuner or the auto tuner in my FT920. In order for me to run the
twinlead all the way into the shack there will be about 18 inches where
the twinlead will share a portal that I constructed to get my grounds
and other cables in and out of the shack. Now I always thought this
was a problem area for twinlead, hence the use of the remote balun.
I am considering the purchase of a new tuner and was thinking I would
like a Palstar Balanced Tuner. But can I use it? Would I be better of
with a T match and a short length of coax to a balun, or would a
balanced tuner be better even with the 18" or so of twinlead coming in
close proximity to the other conductors?
I really can not bring the twinlead in without it crossing paths as I
desribed.
Is a balanced tuner all that better than a T match anyway in terms of
antenna performance or loss?
What say?
Thanks

John
I read that link with great interest. Some years back I saw an article
where twinlead was constructed out of coaxial cable for the purpose of
running it through environments that would be bad news for normal
twinlead. I thought it was rather stupid because the loss on such a
line would defeat the whole purpose of using twinlead. However, for my
purposes where I just need a couple of feet or less to be in close
contact with other cableing, this might work. The question is, why
then are remote baluns promoted as the solution to this common problem?
And, is the coax twinlead and a balnaced tuner a better choice than a
short lenght of very low loss coax, a good current balun, and a T
match?
I am not trying to be difficult, I just want to set this up as
efficinetly as possible. This might actually be the key! I just need
to know if I should go with a short section of coaxial twinlead and a
balanced tuner...or leave well enough alone.

John
I read that link with great interest. Some years back I saw an article
where twinlead was constructed out of coaxial cable for the purpose of
running it through environments that would be bad news for normal
twinlead. I thought it was rather stupid because the loss on such a
line would defeat the whole purpose of using twinlead. However, for my
purposes where I just need a couple of feet or less to be in close
contact with other cableing, this might work. The question is, why
then are remote baluns promoted as the solution to this common problem?
And, is the coax twinlead and a balnaced tuner a better choice than a
short lenght of very low loss coax, a good current balun, and a T
match?
I am not trying to be difficult, I just want to set this up as
efficinetly as possible. This might actually be the key! I just need
to know if I should go with a short section of coaxial twinlead and a
balanced tuner...or leave well enough alone.
Great info!
Thanks!

I am not trying to be difficult,

===========================

There's no need to try - you don't appear to have any problems.

Where did you receive your training?

Now that was helpful !
Maybe you should sign up with the local radio club as an Elmer?
No one is forceing you to read my posts or help me.
Thanks anyway.

On 7 Dec 2004 09:56:10 -0800, "
wrote:

Now that was helpful !
Maybe you should sign up with the local radio club as an Elmer?
No one is forceing you to read my posts or help me.
Thanks anyway.

Jim, I believe you mentioned you were considering the Palstar balanced
tuner -- I looked at the "inside" picture of it, and the variable
inductors look suspiciously exactly alike the variable inductor in my
mfj-989c unit. I'm not saying that's good or bad -- just thought I'd
mention it...

Bob
k5qwg

wrote in message
oups.com...
The question is, why
then are remote baluns promoted as the solution to this common problem?

Well, there's more than one way to skin a cat, a remote balun wouldn't be
bad if it fed the balanced feedline of a resonant antenna which is used at
its resonant frequency. But if you want to operate the antenna everywhere
then you don't want a balun feeding the open wire, weather it be at the
antenna or on the antenna side of a shack side antenna tuner.

Go to Cebiks index section, in particular the Transmission Lines, Impedance
Coupling, and Construction section, - there's lots of reading there on
antenna tuner matching issues including a great tutorial :^)
http://www.cebik.com/radio.html


And, is the coax twinlead and a balnaced tuner a better choice than a
short lenght of very low loss coax, a good current balun, and a T
match?

Oh Yes. If you keep everthing balanced and then use a GOOD balanced antenna
tuner things will work out fine.
Avoid any balanced tuner design that has a matching network followed by a
ferrite core balun on the *antenna feedline* end.
These types of baluns are meant to be used close to their design inpedances,
not when connected to a multiband antenna which is going to have wild
variations in Z.

73,
John

Good info! I think Palstar has a tuner that places a 1:1 balun on the
input or transmitter side of a T match tuner. I think I will look
into that one and use a short length of coax twinlead instead of the
remote balun.
Thanks for the help!
Jim