Unipole Vertical 160 m

                                                                                                                                                           

 

                                                    My TX antenna is a folded monopole and I’m using a relay to shunt the impedance for 80 40m. My                                                       tower is 37m and it is too high for 30m, however I can tune it with my tuner and work DX. '

 

The most important thing is the ground plane, I really recommend a very good ground plane, my backyard has 30m x 50m and because my tower has a folder kit it was necessary to place it 15m from one side.

 

My tower is 15m from the back fence (east), 15m from the house (west) and 15m form the north fence. I laid down 64 radials from the tower to the fence. First I draw a circle 15m diameter and marked all 64 radials equally spaced, and then I extended it until the limits of my propriety. 50% has from 15m to 20 m; the other 50% has from 15m to 40m. One thing I did that helped was a ground rod at the end of each radial. I used 1 m of copper pipe 12 mm diameters.

 

I'm pretty sure the radial system is the reason my TX antenna performs very well. I started using a 21m high tower shunt feed at 8m from inside with a 3" pipe and a 2 capacitor to tune it. The tower was always very well grounded.

 

It is very important to use a metal pipe to run the cable underground from the tower. I used water galvanized pipe, it is galvanized from inside and from outside.

 

a- Metal iron pipe cuts the magnetic field protecting from the strong magnetic field if a light strikes.

b- It keeps the common mode noise very low and you will be pleased with the reception on the vertical unipoles.

c- The pipe works like a radial and ground connection for your station I have a metal box at the base of the tower and another one close to the house. I ground with capacitor and gap arrestor all wires cables; rotor cables etc, any parallel cable induce common mode noise.

 

The picture bellow is the tuning circuit I used with the shunt inside the tower.  My I’m using a different circuit with the skirt.

This called gamma match the BW was only 30 KHz between 1:1,5 SWR.

 

 

 

 

The cage.

That gage impressed me most, first I was able to detune the tower and avoid it the reradiate noise into my receiving antennas,

 

I started using EWE 4 years ago when my tower had 21 m high, the EWE was working very well, then I decided to raise the tower to 37m, I can not use any antenna on the top of the tower with that configuration, only a small hat with 4 tubes 3m long. t

Well making the tower resonant, the reradiation of noise form the TX antenna into the EWE makes the receiver antenna useless.

 

The skirt I used has 32 m long and it works like a ¼ wave stub, grounded at the top and open at the bottom, this works like a ¼ coax transformer and has a very high impedance at the bottom. The high impedance is enough to electrically disconnect the tower from the ground and detune the entire system. It was necessary to use a 47 pf capacitor to tune the skirt to 1830. If you have any other length less then ¼ times .86 velocity factor you can tune it using a small door knob capacitor.