Ladder Line and Interference from Metal Objects
 

Up until now I have avoided considering wire antennas fed with ladder line
like a full wave loop or Zepp, because I have metal rain gutters and
windowframes, which the line would inevitably have to contend with. Is this
a big issue? What kind of an effect do metal objects have on ladder line,
and is this prohibitive to putting one up? Should I stick with coax?

Thank you.

--
R*Horse rwinner.blogspot.com

It is generally not a problem. You can pass a ladder line
directly across a metal frame, and usually you will notice
nothing. Try to keep the lines at right angles to the metal
frame. Passing metal at right angles, for short distances
is rarely a problem. Running lines along side metal can be.
MK

Rockinghorse Winner wrote:

Up until now I have avoided considering wire antennas fed with ladder line
like a full wave loop or Zepp, because I have metal rain gutters and
windowframes, which the line would inevitably have to contend with. Is this
a big issue? What kind of an effect do metal objects have on ladder line,
and is this prohibitive to putting one up? Should I stick with coax?

Thank you.


My installation is as follows: 1) 600 ohm open wire line [tuned of
course!] from the antenna to a protected [from WX] area under the sun
porch. There I simply connected 450 ohm ladder line to the 600 ohm line
for the run into the house. [450 ohm line has increased losses in bad
WX]. As mentioned in another response, I run the 450 ohm line at right
angles over metal structures. I keep the line a least 6 inches from
pipes, heating vents etc and twist the line one twist every three [+/-]
feet.

I run 1 KW 80 through 20 meters with NO interference or RFI in the
shack. This computer is located 3 feet from the amplifier and has no
adverse effects from the amplifier. BTW, my station is grounded
[earthed] IAW electrical code.

Ham op writes:


My installation is as follows: 1) 600 ohm open wire line [tuned of
course!] from the antenna to a protected [from WX] area under the sun
porch. There I simply connected 450 ohm ladder line to the 600 ohm line
for the run into the house. [450 ohm line has increased losses in bad
WX]. As mentioned in another response, I run the 450 ohm line at right
angles over metal structures. I keep the line a least 6 inches from
pipes, heating vents etc and twist the line one twist every three [+/-]
feet.

I run 1 KW 80 through 20 meters with NO interference or RFI in the
shack. This computer is located 3 feet from the amplifier and has no
adverse effects from the amplifier. BTW, my station is grounded
[earthed] IAW electrical code.

Are there any lengths for the xmission line one should avoid when feeding
different types of wire antenna?

--
R*Horse rwinner.blogspot.com

On Mon, 26 Sep 2005 00:29:55 GMT, Rockinghorse Winner
wrote:

Ham op writes:


My installation is as follows: 1) 600 ohm open wire line [tuned of
course!] from the antenna to a protected [from WX] area under the sun
porch. There I simply connected 450 ohm ladder line to the 600 ohm line
for the run into the house. [450 ohm line has increased losses in bad
WX]. As mentioned in another response, I run the 450 ohm line at right
angles over metal structures. I keep the line a least 6 inches from
pipes, heating vents etc and twist the line one twist every three [+/-]
feet.

I run 1 KW 80 through 20 meters with NO interference or RFI in the
shack. This computer is located 3 feet from the amplifier and has no
adverse effects from the amplifier. BTW, my station is grounded
[earthed] IAW electrical code.

Are there any lengths for the xmission line one should avoid when feeding
different types of wire antenna?

Some lengths work better than others, depending on band. See the web
site, http://www.qsl.net/w5dxp and look at the "tunerless" all band
antenna fed w/ladderline.

bob
k5qwg

Bob Miller writes:


Some lengths work better than others, depending on band. See the web
site, http://www.qsl.net/w5dxp and look at the "tunerless" all band
antenna fed w/ladderline.

bob
k5qwg


Thanks fer info. I'll check it out--
R*Horse rwinner.blogspot.com

The reference to Cecil's web site is VG if you do not want to use a
tuner. Cecil does a great job with tuning stubs. I use a tuner.

Some have stated that multiples of 1/2 wavelength can produce RF in the
shack. In 50+ years I have not experienced this. I may be JUST LUCKY!

Do you plan on using a tuner?

Rockinghorse Winner wrote:
Ham op writes:



My installation is as follows: 1) 600 ohm open wire line [tuned of
course!] from the antenna to a protected [from WX] area under the sun
porch. There I simply connected 450 ohm ladder line to the 600 ohm line
for the run into the house. [450 ohm line has increased losses in bad
WX]. As mentioned in another response, I run the 450 ohm line at right
angles over metal structures. I keep the line a least 6 inches from
pipes, heating vents etc and twist the line one twist every three [+/-]
feet.


I run 1 KW 80 through 20 meters with NO interference or RFI in the
shack. This computer is located 3 feet from the amplifier and has no
adverse effects from the amplifier. BTW, my station is grounded
[earthed] IAW electrical code.


Are there any lengths for the xmission line one should avoid when feeding
different types of wire antenna?

Ham op writes:

The reference to Cecil's web site is VG if you do not want to use a
tuner. Cecil does a great job with tuning stubs. I use a tuner.

Some have stated that multiples of 1/2 wavelength can produce RF in the
shack. In 50+ years I have not experienced this. I may be JUST LUCKY!

Do you plan on using a tuner?


Yes, I think I'll buy the MFJ QRP tuner.

--
R*Horse rwinner.blogspot.com

On Wed, 28 Sep 2005 01:11:20 GMT, Rockinghorse Winner
wrote:

Ham op writes:

The reference to Cecil's web site is VG if you do not want to use a
tuner. Cecil does a great job with tuning stubs. I use a tuner.

Some have stated that multiples of 1/2 wavelength can produce RF in the
shack. In 50+ years I have not experienced this. I may be JUST LUCKY!

Do you plan on using a tuner?


Yes, I think I'll buy the MFJ QRP tuner.

The instruction book I got with my mfj 989c tuner has a section on
ladder line lengths to gravitate to, or avoid, depending on band. It
can be downloaded free from the mfj web site.

bob
k5qwg

Bob Miller wrote:
The instruction book I got with my mfj 989c tuner has a section on
ladder line lengths to gravitate to, or avoid, depending on band. It
can be downloaded free from the mfj web site.

Hopefully, the lengths to avoid are associated with specific
loads. Avoiding 1/4WL of ladder-line when feeding a 1/2WL
dipole may be good advice but 1/4WL of ladder-line is ideal
for feeding a one wavelength dipole.
--
73, Cecil http://www.qsl.net/w5dxp