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Window Line New Approach

Antennas

Window Line New Approach

October 2020


Have always had a desire and will sooner or later to get always a perfect match on the various bands both in the lower part cw that in the upper part phone and with possible lower losses in the supply line from the point of supply of various bands until the shack, a kind of dynamic antenna, after the first approach performed in 2015 see http://www.ik1mnj.com/window-line.html the system worked well however I encountered several problems: 1 ) with varying weather conditions rain, snow and ice the conditions of the accord varied with consequent re-tuning of the tuner, 2) under the action of strong wind also seen the width and the exposed surface of the Window line 450 Homs, occasionally it broke the brackets 5mm thick plexiglass which held it away from the boom and other metal staples, consequently I had to replace them, 3) the antenna switch was made with Omron 16 amp socket bipolar relays which supported b enissimo the 500 watts of my Ten-Tec Hercules II, later I bought the Acom 2000 consequently I rebuilt the Antenna Switch using the most performing relays Finder series 66, two poles 12v cc 30 Amp, I tested them with 1500 watts key down, no sagging I found, they work very well, the Antennas have remained the same as before, that is: five Quad elements in 6/10/12 m., 4 Quad elements in 15/17 and 20 m., 3 Yagi elements in 30 and 40 m. interlaced on the same boom, the inverted Vee dipole on 80m, and as a novelty I added the inverted Vee for 60m. 5.350 Mhz.
With these improvements in mind I proceeded as follows: I dismantled the entire system, putting into practice these new solutions that I am going to describe: first I built the Antenna switch and I used the new 30 Amp Finder relays, I replaced the 450 window line homs with a 300 homs, much narrower and I intubated it in 16 mm diameter pvc tube that run equidistant from each other from ten band new Antenna switch to each of the ten Antenna feed point, each curve or joint of the pvc tube are glued to avoid infiltrations of water, I have also improved the anchoring of the Window line on the lift trolley, protected by a flexible pvc tube, and made the rotation around the mast more efficient, from the lift trolley it goes down intubated in a flexible tube in pvc at the base of the pylon, here I built a three-way switch always with the Finder 30 Amp two-pole switching relays that gives me the possibility of two other inputs with window line 300 Homs in addition to the one that goes up to the Antenna Switch 10 bands, the relays at rest put the window line on the ground, at this point the Window Line is intubated in two pvc pipes for electrical systems, one inside the other of adequate measures, all enters an underground pipe in 10 cm diameter pvc that already pass the rotor cables and a pair of RG 213 coaxial cables for a possible use in addition to the auxiliary cables for switching relay band and 12 V dc power supply, this solution of two pvc pipes one inside the the other where the Window Line passes is a variant of John's W6NBC project which uses polyethylene foams tube (see QST August 2018) Thanks John! and thanks also to Gian I1POR who find this Article on QST, all the cables arrive on the external wall of my house just behind the Shack, here or built a manual disconnector inserted on the Window Line so as to be able to isolate the line in case of inactivity or for protection from electrostatic discharges caused by atmospheric perturbations, from here the line enters the shack through two paired RG 213 coaxial cables of equal length and goes directly to a Balun 4:1 then to the J.W.Miller AT 2500 Antenna Tuner.
Regarding the respective tune on the various bands, I manually act on the tuner (even if it has the automatic tune possibility ... because it is a bit slow) following a preset table, the tune are always very stable and fast to perform.
Generally the whole systems working very well but to be honest still some little understandable problems arise that is to have really right lengh of Window Line for the frequenzy in use, due to many and varius band its not possible to have an right lenght of Window Line that match every bands, is still a compromise, i note some RF in Shack with the Band wich have not a right lenght of Window Line, in my situation as it is now, i have slight RF in the shack in 40m. and 15m. is not a big problem but upset my PC ...... the next step I have to do something to solve this problem with some solution such as shortening and lengthening the Window Line with a series of relays, we will see what to do ...



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