[TowerTalk] Re: Open ladder line question
DGB
DGB" <dgbcms@netnet.net
Thu, 26 Jul 2001 05:16:13 -0500
I have a similar setup with 92 ft. of 450 ohm ladder line
with my shack in the garage.
What I did was cut off several segments of 4" dia. pvc about
2" long. Then I epoxied inside and across the dia. at one
end of the tubing, a 1/4 thick x 1w" piece of
non-conductor. In the center of that flat I drilled a hole
for a galvanized drywall screw that allows me to screw them
to the side of the building. I put a row of them up near the
top of the wall, staying about 8" away from the aluminum
eve, and another row about a foot from the ground. I looped
or zig-zagged the surplus length of ladder line up and down
around these and fasten the ladder-line to them with plastic
ties.
It works great and have notice no interaction with the
electrical wiring that runs thru the wall.
73 Dwight W9YQ
----- Original Message -----
From: <K7GCO@aol.com>
To: <towertalk@contesting.com>; <Bgsalesmel@cs.com>
Sent: Thursday, July 26, 2001 0:42 AM
Subject: [TowerTalk] Re: Open ladder line question
>
> In a message dated 7/24/01 10:49:43 PM Pacific Daylight
Time,
> Bgsalesmel@cs.com writes:
>
> Hello,
> Name is Mel, KD7DCR, here and I am new to this ham radio
gig. I am just
> getting my first station set up, tower up, etc. this
summer.
>
> You seem to "flat know" your stuff about ladder line
applications and I
> have a basic question: i.e., How do you install your 123'
or 135' of line
> when the center connector is only +/- 45 ft from your
operating
> position/single point entry? This is a dipole design from
CQ mag of about 3
> or 4 years ago and in it they suggested using 66' to 125'
of 450 ohm line. It
> is about 140ft long made out of house grade Romex, center
at 70ft naturally,
> with the 3-cond "dasiy chained" for an effective length of
+/- 210ft per
> side. I personally think this will "look" like a 3/8" OD
single conductor due
> to induction - but, who knows: If it plays well and works
for me here, I
> don't care if it thinks it is 10ft long! Tuner will be a
MFJ-949E that
> accepts and switches 450 ohm line directly.
>
> I can only put up a 40ft tower here to start - will
fight the permit battle
> when I can afford a self-supporting one in about 2 years.
In the mean time,
> make do with what I can afford and do now. Dipole will
hang off of this tower
> at the 32 to 34ft level, with a Unistrut/pulley assembly,
and the other end
> will be at about 22ft on a pole in my garden. Side lobe
will be centered at
> about 020 deg (true - not mag) by 200 deg.
>
> I have an XYL that objects to "wires hanging all over
the place", etc. and
> need to keep this "looking" very sanitary. I have a blank
wall of the house,
> about 9ft tall x 14ft long, T-111 wood siding, right
beside my entry to the
> basement operating position. This is behind a green bush
right now, it would
> be in the open during winter months.
>
> Is there any way to "loop" or "zig-zag" this excess
ladder line on this
> wall before going down into the shack? The eve has a metal
rain gutter,
> everything else is wood. Will be using one of the
Wireman's QST grounding
> spark plug devices before heading into the shack, and a
knife switch inside
> as well. I intend to disconnect from all ant and power
when not working.
>
> Top ant on the tower is Force12 C-4.
>
> Thanks if you can shed some light on my question.
>
> Regards & 73's,
> Mel Frost
> Coeur d'Alene, ID >>
>
> Mel: Looping and zig zagging is about the only way to use
up the excessive
> open wire length or live with the higher reactive loads of
short length
> feedlines if the tuner will match them. If you can get
1:1 SWR on the coax
> to the rig and no arcing or warming of the tuner, you have
maximum transfer
> of energy into the input of the feedline and into the
antenna minus the loss
> in the feedline what ever it is. Matching at the input of
the feedline is
> the most important match.
>
> I'm going to make a "Ferris Wheel Spiro" to use up
excesive length. The
> spacing will be about 2' between the line. Right angle
bends are not
> recommended. I'll grid dip it before and after. The
Ferris Wheel can be on
> a post or on the side of the house.
>
> I have in the past had a 2 ganged 2 pole switchs so I
could swtich in
> certain lengths of open wire line so as to obtain a Hi-Z
or a Lo-Z for the
> tuner. This is practical for the higher frequencies. You
don't always need
> a tuner with typical Lo-Z's around 50 ohms reflected to
the end of a 1/2 wave
> multiple feedline. I have found you can feed and open
wire line directly
> into the unbalanced 50 ohm output of a rig or in my case a
coax switch
> without RF in the shack. I add a series BC 3 gang
variable in the grounded
> or shield lead. Connect the rotor to the shield or ground
connection.
> Resonate a dipole or vertical antenna low in the band and
using a feedline
> that is a 1/2 wave multiple, you can often obtain a low
SWR and/or resistive
> load easy over the whole band to match by even the 50 ohm
rigs in many cases.
>
>
> In the "Old Days" of "Link Coupling," one could have a
balanced or
> unbalanced output with a series variable to obtain a
resistive load to the
> final even with SWR. Band edge operation was not a
problem it is now with 50
> ohm output finals. With a resistive load one could swing
the link in an out
> for any power level desired without having to redip the
final. With the
> right number of turns in the link one could reflect the
optimum load to the
> final for max output for loads of 30 to 1000 ohms also--no
tuner. You just
> had the inconvenience of changing tank coils. So all Art
Collins did for you
> with the band switching Pi is to eliminate plug in coils,
lower the Z
> matching range and allow only an unbalanced load. You
could match higher
> SWR's on coax but at a lower final efficiency. I have
built a blanced Pi
> output final for push-pull tubes and it's great for open
wire line of Hi/Lo-Z
> loads. I still have my old Pr-813's final and will
perhaps just add 2 more
> 813's.
>
> With open wire line you don't have to worry about your
feedline losses going
> up in time and feedline damage is easily seen and
repaired. It is not with
> coax. I also still have and open wire line I made in the
30's. That's great
> feedline economy. k7gco
>
>
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