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[TowerTalk] Getting Open Wire Feeds Into the House (Shack)?

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Subject: [TowerTalk] Getting Open Wire Feeds Into the House (Shack)?
From: (
Date: Mon, 15 Nov 1999 04:17:18 EST
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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