On Wed, 21 Apr 2004 20:47:47 GMT, zeno wrote:
Although I have the acres (7) there are a lot of buildings (old barns etc.),
trees, etc. My antenna planning has to dodge many many obstacles actually. This
is an old chicken ranch and there are building everywhere, then all the trees.
Are you saying that a rhombic could be put up on the same masts more or less
(only one of the masts is potentially moveable, meaning that it would only be
diamond like at one end of the trapezoid. This rhombic would be instead of the
540' loop?

I will look up rhombic in the books and see what gives.

Hi Bill,

No, this time shape matters as it is a function of all angles of
radiation combining to ADD rather than jumble. Again, think in terms
of the supports/mast merely being the outer, irregular perimeter to an
ordered interior antenna shape.

The Rhombic would BE the 540' loop. Normally it is open or terminated
at the end opposite the feed point, but having the shape anticipated
is more the work than this simple change. (It has the same feed
considerations, complete with your expected twin lead.)

Congrats on your desired call.

73's
Richard Clark, KB7QHC

for starters a good contest alternative: Toronto Alaska Japan

and for the hometown crew: Tasty Apricot Jelly or Typical Antique
Junk

Cecil Moore wrote:

zeno wrote:
Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet.

Now we will have an endless thread of words to match your
TLA (three letter acronym). Transmitting All Joules?
--
73, Cecil http://www.qsl.net/w5dxp

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The problem, as I see it, with using the fixed masts as outside perimeter
configuration support structure for the specifically ordered interior shape is the
sag the inevitably occurs when wire is a rope and pulley distance away from the
supporting mast. I already see this with the tree supported antenna. The ropes drop
down and the wire is 8' or so lower than anticipated. This seems critical when the
masts are only 50' to begin with. How high, or shouls I say, what is the minimum
height for an acceptable Rhombic?

Bill, K6TAJ

Richard Clark wrote:

On Wed, 21 Apr 2004 20:47:47 GMT, zeno wrote:
Although I have the acres (7) there are a lot of buildings (old barns etc.),
trees, etc. My antenna planning has to dodge many many obstacles actually. This
is an old chicken ranch and there are building everywhere, then all the trees.
Are you saying that a rhombic could be put up on the same masts more or less
(only one of the masts is potentially moveable, meaning that it would only be
diamond like at one end of the trapezoid. This rhombic would be instead of the
540' loop?

I will look up rhombic in the books and see what gives.

Hi Bill,

No, this time shape matters as it is a function of all angles of
radiation combining to ADD rather than jumble. Again, think in terms
of the supports/mast merely being the outer, irregular perimeter to an
ordered interior antenna shape.

The Rhombic would BE the 540' loop. Normally it is open or terminated
at the end opposite the feed point, but having the shape anticipated
is more the work than this simple change. (It has the same feed
considerations, complete with your expected twin lead.)

Congrats on your desired call.

73's
Richard Clark, KB7QHC

On Thu, 22 Apr 2004 00:20:50 GMT, zeno wrote:
The problem, as I see it, with using the fixed masts as outside perimeter
configuration support structure for the specifically ordered interior shape is the
sag the inevitably occurs when wire is a rope and pulley distance away from the
supporting mast. I already see this with the tree supported antenna. The ropes drop
down and the wire is 8' or so lower than anticipated. This seems critical when the
masts are only 50' to begin with. How high, or shouls I say, what is the minimum
height for an acceptable Rhombic?

Hi Bill,

Think positively: how high will they be? 40 Feet? 10 Meters? One
quarter wave for 40M? This is not a hardship case. One half wave or
better high for 20M and above? No one's gonna let you cry in your
beer there either. And now for the classic "testimonial": it's gonna
be boomin! (what choice do you have?).

As a cautionary, don't try to pull out the catenary. The tension
rises with the tangent of the of the deflection angle. If you could
achieve perfect flatness, a breeze would snap the line.

73's Richard Clark, KB7QHC

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.