June 2009 During the early months of 2009 the high winds & gales caused damage to the top load on my vertical LF/MF antenna. I lowered the mast and removed the assembly to enable me to carry out a repair. As in the past I have had considerable difficulty getting the top load on and off the mast due to it fouling the ladders I have to use to remove it due to the close proximity to the house wall, at times my acrobatics on the ladder proved to be unsafe and rather dangerous. So I decided to modify the shape of the capacity hat from square to to an oblong bow tie shape so it would not interfere with the ladders during maintenance.
I used the same central hub and plastic supports in the new shape and used a 1.5mm insulated 7 strand wire for the capacity hat and integrated tensioning wires which were all soldered together as one structure. As I had some success previously with a spiral top load antenna I also constructed a small 12 turn spiral using the same wire on the plastic supports just below the wire structure to be connected in series with the vertical wire and the capacity hat.
The inductance of the coil is 160uH and as before the vertical radiator is 8 insulated 16/0.7mm stranded wires twisted like Litz with a mid-point inductor of 500uH.
September 2009 Having been operating on the 500 kHz band for some while now I felt that I should continue with my previous idea of making a separate loading coil for 136 kHz. I wanted a compact coil making it easy to add or remove from the 500 kHz coil already there. After reading various articles I constructed a “Wave Wound” coil, this is similar to basket weave but produces a tubular construction rather than a pie shape. Unfortunately I was unable to achieve the inductance value I required within the constraints of the physical size, 150 metres of wire produced only 1.7mH. Now the challenge is to try the pyramid winding method. See links page for article.