[Elecraft] Ladder Line near the gutter.

[Dan Barker]

My antenna is an 80 meter dipole up over the house. The feed line is =
Ladder. The line descends vertically to the shack. It passes through the =
bottom of the eave and up into the attic, thence back through the shack =
ceiling to the balun and rig. Everything within a foot of the line in =
the attic area is wood or nails. However, the line goes right past the =
gutter, which is metal.

I need to secure the line from wind movement anyway, so my question is =
this. How far from the metal gutter should I secure the line? I've not =
seen any literature (although I'm SURE it exists somewhere) as to how =
far to make it. I've definitely seen admonitions not to run the line =
against any metal.

Side note. The above refers to my new (soon, hopefully very soon) QTH. =
My present QTH has the line sometimes laying on the ground (depending on =
the wind and temperature). Should I elevate it? If the ground matters, =
this is Georgia. It's standard issue Georgia Red Clay with gravel =
admixture, of course!

Dan / WG4S / K2 #2456

O Dipole (end view<g>)
|=20
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|=20
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| / \
|XX | YY |=20
\______/ |
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4:1
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\____ coax rig=20

XX =3D Gutter
YY =3D Exterior wall just above ceiling level.

I'll probably run the line through some 1 1/4 PVC plumbing pipe secured =
to the eave and missing the gutter by X inches.

[Dan Barker]

Cool. Luckily I have a fire extinguisher. But at five watts, I may not =
need it. I think I'll use PVC elbows, toggle bolts, and discuising =
paint. I need to handle 70 knot winds so I'll skip the spring and just =
replace it occasionally. My ladder line is Store-Bought - about 1 inch =
spacing.

Dan / WG4S / K2 #2456



-----Original Message-----
From: Tom Hammond NOSS [mailto:***@earthlink.net]
Sent: Monday, February 11, 2002 10:45 AM
To: Dan Barker
Subject: Re: [Elecraft] Ladder Line near the gutter.


Dan:

I 'stood-off' my 3" home-made ladder line from the gutter about 12". =
I'll=20
ATTACH a (GIF) drawing of how I did it.

I also passed the ladder line THRU the window into the shack by =
replacing=20
the upper pane with plexiglass and then drilling a couple holes for =
screws=20
in the pane. This was, I could screw-attach the wires on both sides of =
the=20
window without compromising the thermal insulation.

Note that, one time as a result of a winter storm, the ladder line got=20
'pushed' up against the outside bottom corner of my wooden support and=20
(sometime after the storm) my 1KW RF caught the support ON FIRE! Damnear =

burned the moutnig bracket off the house!

Good luck.

Tom


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[George, W5YR]

Dan, try to keep ladderline as far from any other objects as is reasonably
possible. Probably a few inches from metal is more than adequate. As far
away from the earth ground as possible - laying on the ground or being
coiled or wadded up like coax is a no-no!

You might find that a 1:1 current or choke balun works better on average on
all bands. I use three ladderline-fed antennas here with three W2DU bead
baluns and they tune very well from 80-10 meters.

72/73/oo, George W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
Amateur Radio W5YR, in the 56th year and it just keeps getting better!
QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771
Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437

All outgoing email virus-checked by Norton Anti-Virus 2002

[Vic Rosenthal]

Post by Dan Barker
My antenna is an 80 meter dipole up over the house.
I need to secure the line from wind movement anyway, so my question is this. > How far from the metal gutter should I secure the line?

A couple of inches is fine. Just make sure it is perpendicular to the gutter
and does not run parallel to it.

Post by Dan Barker
Side note. The above refers to my new (soon, hopefully very soon) QTH. My > present QTH has the line sometimes laying on the ground (depending on the wind > and temperature). Should I elevate it?

It is probably best that it not be on the ground. Especially if it could be
lying in a puddle of water!

73,
Vic, K2VCO
Fresno CA

[Ron D' Eau Claire]

Post by Dan Barker
I need to secure the line from wind movement anyway, so my
question is this. How far from the metal gutter should I secure
the line? I've not seen any literature (although I'm SURE it
exists somewhere) as to how far to make it. I've definitely seen
admonitions not to run the line against any metal.

The "rule of thumb" published in the ARRL handbooks for many years was
this: "The minimum separation between either conductor and all other wiring
should be at least four or five times the conductor spacing..."

That would include any conductor or any lossy dielectric. The earth is a
very lossy dielectric. Keep the open wire line well away from it to avoid
using your r-f to warm the earthworms.

The idea is to keep the two currents in the open wire line equal and out of
phase at all points. If you accomplish that, the open wire line will not
radiate significantly. The field created by current flowing in one wire will
exactly cancel out the field in the other wire. In theory, that will only be
true of both wires are exactly in the same place - an impossible situation.
In practice, the cancellation over the HF range is excellent provided the
spacing is on the order of 2 to 6 inches (5 to 15 cm) with the narrower
spacing preferred on 28 MHz.

Feeding the open wire line from a balanced source and connecting it to a
balanced load at the antenna are two steps toward having a balanced and
out-of-phase current in each line. If you allow the line to run where one
conductor can capacitively or inductively couple to surrounding objects more
than the other conductor, you will also introduce unbalance as well as lose
r-f. So wherever you are running it, try to keep it away from objects and
keep each conductor equidistant from whatever objects you must pass close
by. Also, try to pass objects at right angles to minimize the amount of
coupling.

If you are planning on running the line at a high SWR, keep in mind that
very high voltages can exist at points along the line. Separation and
insulation are very important, not just to avoid losses but to prevent the
possibility of starting a fire in combustible material. A little dust on the
insulators holding the wires or against something they are touching and you
can have a flashover that can start a blaze. Not a happy prospect,
especially in a hidden corner of an attic.

Those high voltages are also why true open wire line, with a minimum of high
quality insulators holding the wires, is far preferable to the common
'ladder line' or, worse, 'twin lead'. Where the wires do have to touch
something, such as the spacers holding them, you want the very best
insulation you can get.

Ron AC7AC
K2 # 1289

[Ron D' Eau Claire]

Luckily I have a fire extinguisher. But at five watts, I

may not need it. I think I'll use PVC elbows, toggle bolts, and
discuising paint.>
Dan / WG4S / K2 #2456

True, but I have melted plastic insulators on open wire line at about 10
watts when they happened to be right at a high impedance point! Fortunately,
that was at the banana jacks on the back of my ATU where the line
terminated, so I could smell it as well as see it on the SWR meter in the
line to the ATU.

Use the best insulation that you can get at all points. If you can find
them, those old ceramic feed-throughs that were used for "knob and tube"
house wiring years past ought to be excellent for guiding the conductors
through a wall. That's exactly what they were designed for although at 60 Hz
instead of HF. Every time I come across one I pick it up and put it in the
antenna goodie box.

Ron AC7AC
K2 # 1289

[Stuart Rohre]

A good means to standoff is the Radio Shack standoffs for 300 ohm twin lead
that are about 7 inches or longer. Some screw into wood, or clamp to mast.

PVC ones can be made.
Home Depot sells electric fence standoffs in a bag of 25 for $5 or so.

The rule of thumb is at least twice the spacing of the line, but since you
are crossing at right angles, it is minimal interaction anyway.
73,
Stuart K5KVH

[N***@aol.com]

Folks,

Been reading all the stuff about balanced tuners,
unbalanced tuners, choke baluns, bead baluns, etc.

Here's a "must read" on the subject:

http://www.vcnet.com/measures/bbat.html

Although he uses ganged roller coils, there's no reason
switched coils couldn't be used instead. Note that this
design works for balanced or unbalanced loads.

73 de Jim, N2EY