Amateur Radio Pages
updated November 2014
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LF and MF Experiments etc - 1
November 2003
During the first of my experiments with the cane prototype “Spiral Top Mk1”. It was very promising when only attached to the rear of the garage  at about 3 Metres above ground. Unfortunately the cane construction weakened in the rain and was destroyed by the gale winds, so I didn't even get it up on the mast. My next work is going to be more ambitious than my first which finished up in much the same way as Alan & Finbar's.

March 2004
The new construction, “Spiral Top Mk2”  is much stronger & I believe lighter, it has 2 double wound spirals whose diagonal lengths are 2 metres (the cane one was about 3 metres). The 1 Metre supports of PVC electrical conduit are mounted on a quad loop spider centre and rotated by 90 deg so that the spiral is parallel to the ground, each spiral has 28 turns of wire (14 on top of the conduit and 14 below) spaced at 50 mm. When the 2 double spirals are assembled the inductance is measured at 1.65 mH (whilst at ground level). The spiral assembly was completed and a horizontal fibreglass standoff arm mounted so as to separate the vertical antenna section from the mast supporting the spiral.
September 2003
In my small back garden of 50 feet x 25 feet (15 metres x 7.5 metres) it is not feasible to erect a Marconi type vertical antenna with a conventional two or three wire “T” type top load so during my efforts to produce a reasonably efficient small LF antenna for my small back garden I have documented the experiments during this challenge based on the spiral inductively top loaded antenna as in the article in “Technical Ideas and Current Projects” at Alan Melia’s (G3NYK) web site, access from my links page. Other ideas followed.

October 2003
My first antenna made with LF in mind was the “Umbrella” type as seen on the right, this (I thought at the time) was quite successful but as most of us in the hobby strive for improvements to antenna  and equipment I decided to carry out further experiments and tests.
I was surprised to find that when installed on the mast at about 10 metres (35 feet) I had to place extra inductance at the base of the antenna to resonate the it on the 136 kHz band. My previous "Umbrella" type top load having a steep angle and coming quite close to the ground that the top load capacitance was higher than with the spiral top load.

I now also realise that the steepness and length of the umbrella top load was restricting the efficiency and radiation of the vertical part of that antenna by reducing the effective height of the antenna..........Continued next page......
LF & MF experiments 2