Is open wire so "superior" to today's coax that it's worth all this?
> 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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