What are the units of distance? Inches? CM? MM?
For 300 ohm ladder line, I get .390.

Thanks



On Tuesday, March 30, 2004 at 8:43:04 PM UTC-5, Tom Bruhns wrote:
Impedance is about 120*ln(2*D/d) ohms, where ln is the natural
logarithm, and D is the wire spacing, center to center, and d is the
wire diameter. Assumes round wires, and air dielectric. You can
rearrange that: if you want x ohms and have d diameter, D =
d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you
don't have a calculator that handles that sort of math, this table
will probably get you close enough:

D/d impedance, ohms
1.9 150
2.8 200
6.2 300
22 450
75 600

Construction depends a bit on how much you're making and what you have
available for materials and tools. People used to use wooden spacers,
boiled in parafin wax. Someone gave me a bunch of PETE
tensile-strength test strips that are a good size. You can make
spacers from PVC pipe. You can thread wires through holes (generally
not so efficient), or fit wires into notches and secure by with a
plastic or wire wrap, or by melting the wire into an undersized notch,
or with various glues. Undoubtedly lots of other ideas, both
tried-and-true and just waiting to be tried for the first time.

You can drill holes through the glass and install feedthroughs (but
probably not if it's double-pane!), or drill a couple over-size holes
through the wall or possibly through a wooden window frame member, or
install a wood or plastic piece in a partially-open window. You can
also possibly inductively or capacitively couple through the window.
If you decide to go through wood or wall materials, plan to make
oversized holes, lined with decent electrical/RF insulation. What
strikes your fancy?

Cheers,
Tom


Larry Gagnon wrote in message ...
Hello to all. I intend to erect an 80 meter full size dipole and feed
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.

Larry Gagnon VE7EA

In article ,
says...


What are the units of distance? Inches? CM? MM?
For 300 ohm ladder line, I get .390.

Thanks



On Tuesday, March 30, 2004 at 8:43:04 PM UTC-5, Tom Bruhns wrote:
Impedance is about 120*ln(2*D/d) ohms, where ln is the natural
logarithm, and D is the wire spacing, center to center, and d is the
wire diameter. Assumes round wires, and air dielectric. You can
rearrange that: if you want x ohms and have d diameter, D =
d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you
don't have a calculator that handles that sort of math, this table
will probably get you close enough:

D/d impedance, ohms
1.9 150
2.8 200
6.2 300
22 450
75 600




It does not matter what the units (inches, cm, feet) are as long as you
use the same. Say .1 inches in diameter and 3 inches spacing or 1 foot
in diameter and 30 foot spacing although that is an awful example but
could come into play with VLF or even power line frequencies.

The units cancel each other out and it is just a ratio of diameter and
spacing.

Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

One of many ways is to use plastic coathangers for spacers. These are
readily available, and have the added advantage that you can choose your color.
Just chop them up to whatever spacing you desire.
If you are planning on just a single band antenna, I would feed it with coax.
However, if you are going multi-band with a tuner, use the open wire line.
The Impedance is not critical. Use 2" to 6" spacing.
73 Gary N4AST

On Tue, 30 Mar 2004 19:52:50 -0000, Larry Gagnon
wrote:

Hello to all. I intend to erect an 80 meter full size dipole and feed
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.

Larry Gagnon VE7EA

As an alternative, you can try the website for w7fg. He makes and
sells open ladder line, as well as dipoles with the ladder line
attached.

bob
k5qwg

I have a G5RV made by W7FG. The construction is great and makes structural
sense. I can recommend his version highly.

Its easy to put up and you dont have to worry about the center connection
coming loose..*there is no center connection*

He uses one continuous wire from feeder to end of the dipole on each
side..smart...

Mitch KD4HTW


"Bob Miller" wrote:
As an alternative, you can try the website for w7fg. He makes and
sells open ladder line, as well as dipoles with the ladder line
attached.

bob
k5qwg

I made some ladder line last year. It works well, but was very time
consuming. I now buy it.

I purchased wire "staples" These are plastic bridges with holes for nails.
You pull out the nails and install your feed line.

There is a photo of a 1/2 inch section at this URL.

http://user.mc.net/~jdewey/Ham_radio...ding_relay.jpg

I used larger staples for my main feed line.

http://user.mc.net/~jdewey/Ham_radio/doublet.jpg

John
KA9CAR



"Bob Miller" wrote in message
...
On Tue, 30 Mar 2004 19:52:50 -0000, Larry Gagnon
wrote:

Hello to all. I intend to erect an 80 meter full size dipole and feed
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.

Larry Gagnon VE7EA

As an alternative, you can try the website for w7fg. He makes and
sells open ladder line, as well as dipoles with the ladder line
attached.

bob
k5qwg

What is a good type of wire to use? Stranded ok? Insuluated ok? what is best?

Zeno

KA9CAR wrote:

I made some ladder line last year. It works well, but was very time
consuming. I now buy it.

I purchased wire "staples" These are plastic bridges with holes for nails.
You pull out the nails and install your feed line.

There is a photo of a 1/2 inch section at this URL.

http://user.mc.net/~jdewey/Ham_radio...ding_relay.jpg

I used larger staples for my main feed line.

http://user.mc.net/~jdewey/Ham_radio/doublet.jpg

John
KA9CAR

"Bob Miller" wrote in message
...
On Tue, 30 Mar 2004 19:52:50 -0000, Larry Gagnon
wrote:

Hello to all. I intend to erect an 80 meter full size dipole and feed
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.

Larry Gagnon VE7EA

As an alternative, you can try the website for w7fg. He makes and
sells open ladder line, as well as dipoles with the ladder line
attached.

bob
k5qwg

zeno wrote:
What is a good type of wire to use? Stranded ok? Insuluated ok? what is best?

I made mine cheap out of #16 stranded insulated house wire available at
Home Depot.
--
73, Cecil, http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

If one is constructing ladder line, is the point to design the ladder line
so its impedance matches the characteristic impedance of the antenna
itself at its feed point?

The theoretical feed point impedance for a full wave loop antenna is
approximately 100 ohms, (but this does change, and is dependent upon
antenna height above ground, near-by structures, and ground conductivity.)
Should I try to make my ladder line to get as close as possible to this
100 ohm? In other words, does it make any difference reallly if my (12
guage insulated) ladder line uses 4" spacers (550 ohm) or 2" spacers (468
ohm) or 1" spacers (385 ohm) in the final analysis? Should I just go with
the 4" spacing because it looks cool?

Anyone think that maybe non-insulated would be a better way to go?

Zeno


Larry Gagnon wrote:

Hello to all. I intend to erect an 80 meter full size dipole and feed
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?

Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.

Larry Gagnon VE7EA

--
********************************
to reply via email remove "fake"

zeno wrote:
If one is constructing ladder line, is the point to design the ladder line
so its impedance matches the characteristic impedance of the antenna
itself at its feed point?

The point of using ladder-line is so the antenna impedance doesn't
matter (within reason). SWRs on the ladder-line range up to 30+:1
with small ill effects. A 30:1 SWR on ordinary coax is a signal
killer.

Consider that the feedpoint impedance of an all-HF-band antenna
might range from 60 ohms to 3000+/-j3000 to 6000 ohms. The SWR on
Z0=600 ohm line would be around 10:1. The SWR on Z0=50 ohms would
range up to 100+:1.

The theoretical feed point impedance for a full wave loop antenna is
approximately 100 ohms, (but this does change, and is dependent upon
antenna height above ground, near-by structures, and ground conductivity.)
Should I try to make my ladder line to get as close as possible to this
100 ohm?

Nope, go for simplicity. There's not much practical difference between
Z0=400 ohms and Z0=600 ohms. And you may be able to use the impedance
transforming properties (on a line with reflections) to your advantage.

Anyone think that maybe non-insulated would be a better way to go?

Non-insulated wire allows one to hang parallel stubs up and down the
line, useful for matching purposes. It also allows one to measure
actual feedline voltages.
--
73, Cecil, http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----