In a message dated 14.11.99 20:40:51 Pacific Standard Time, K7GCO writes:
<< In regard to running open wire line into a basement:
I ran open wire into the basement by drilling 1/4" holes in the house
wall of wood and ran insulated open wire line through the holes into a
basement. This hole is easy to plug and paint later. You can slip a sleeve
insulator in a bigger hole if you like. I ran the open wire line across the
basement ceiling on stand offs and drilled holes in the floor at the junction
of the floor and wall and ran the wires there beside the rug into the first
floor. If you no longer use it, the edge of the rug covers in the holes. I
ran lengths of RG8X up in the first floor the same way. Or replace a glass
window with Plexiglas and run the open wire line and/or coaxes right through
it. When finished, replace it with the original glass later.
Open wire line and the proper tuner is a great system and I've used it
for over 60 years. I use lengths that are 1/2 WL multiples to reduce
reactive Z's. Use 492 X .95 VF / 3.55 MHz. That's the magic length for all
bands with the 1/2 WL multiple least error. Suspend the open wire line off
the ground at least 5', short both ends and Grid Dip it to 3.55 MHz. Use
solid enameled or insulated wire. The spacing can be 4-6" and the Z of the
open wire line is not critical--only the length for ease of matching. The
parallel and series configurations shown in the ARRL Handbooks were written
by those who never used them year after year. The Series configuration for
low Z loads is difficult to get to work. A series Xc variable is needed in
the link (ground the rotator) or you will have trouble getting matches
and/arcing with either one. Use RF ammeters or light bulbs shunted with just
the right amount of wire in the output for balance and maximizing output.
Use light bulbs with pig tails and clips and adjust shunt length for
brightness. To extend low range RF ammeters range, shunt with knife
switch--for 2 ranges. Or you can just clamp it right on the wire. RF
ammeters are getting hard to find now--I bought them all. Experiment with
different LC ratios in the tank circuit and number of turns in the link for
maximum output or no arcing. Start with 2 turns. I've even used coax with a
half wave of coax connected to give a balanced coax to feed an ungrounded
link on 6M. This tuner was balanced on both ends. No TVI on 6 m either. A
2 element quad was fed with 100 ohm balanced coax.
The Johnson MB with the modifications I've given on TT is the best
tuner of all to use. If you ever use it to match 100 ohm balanced coax there
is at trick you must know or you can get into trouble. I found this out when
I had RF ammeters in each leg and SWR bridges in each of the 50 ohm series
connected coaxes. What can happen is not believable unless you see it and is
highly disputed by those who have never seen it and are experts in everything
from child birth to reincarnation without ever experiencing either? The cure
is also simple.
I also use a balanced L network with 2 variables and inductors all on
one shaft. It has this strange thing happening also with a simple cure.
This tuner matches a variety of balanced loads with smaller components also.
I had one installation where I had 750 watts in the 50 ohm link (RF
ammeter in link and 1:1 SWR) and 700 watts in the antenna using 450 ohm line
and a balanced 150 ohm quarter wave coaxial stub and a balanced 28 ohm
coaxial stub to match 16 ohms at a beam. There was 3.87 RF Amps in the
Collins KW-1 RF ammeter and the tuner RF ammeter in the link 1/4 WL away of
50 ohm coax on 20 M. You have 1:1 SWR if 1/4 WL away the current is still
the same (I didn't have a 50 SWR bridge then). I later made one of coax
similar to the "Twin 'Bulb 300 ohms SWR Indicator." I still have a picture
of the tuner from 1953--and the KW-l. The SWR was flat on the 70' of 450
line. I could take an RF ammeter and shunt it on either line anywhere and it
read the same value of 1.27A as I remember. .3 dB loss is not bad from input
to tuner to input to antenna--if not a record (6.61 A in the feedpoint).
If you have 1:1 SWR at the input of the tuner and nothing is heating or
arcing, you have 100% transfer of power less the feedline and tuner losses.
There are some exceptions. The one main advantage of a tuner and open wire
line is that you can get maximum transfer of power all over the band also.
All the coax problems, high cost and limitations go away. Rain has no
affect--isn't that nice? I have one length of open wire line I made 60 years
ago I still use--enameled #12. #12 or 10 House wire with the plastic
insulation works well. Don't use stranded bare copper wire. I use insulated
wire now and it has a lower velocity factor depending on the insulation--and
the number of spacers for any wire. Keep it 1' away from the tower.
Open wire is blazing a comeback. The 450 ohm ladder line is fairly good
up to 1 KW . Even 300 ohm ribbon can be used with low loss with loads of
200-400 ohms. this minimizes the current in the small wire. Rain will upset
the dielectric. Coat it with wax.
Spacers can be made our of most any plastic not susceptible to UV.
Don't use wooden dowels boiled in wax. I could hear arcing in the spacers at
600 watts. 3/8" delrin is a great spacer. Drill holes in the ends that just
slip over the wire and secure it's position every 1 1/2'-2' with epoxy or
silicone rubber. Use heavy soldering lugs at the ends.
I'll have long runs of 1/2 WL multiple lengths on all bands (my magic
lengths) at my new QTH in SD and I'll use open wire line. There are many
tricks in it's use. I'll be using rhombics also. I have made and
accumulated a large number of tank and rotary coils of 1 KW, 500W, 150W and
75W coils from flee markets over the years. Get a Johnson MB. ARRL usually
says to use any length of open wire line or seldom recommends certain
lengths. They have set back tuners and open wire line more than anyone as
many have trouble with their recommendations--they never test them. Open
wire needs good supports for ice loading.
k7gco >>
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