As my main interest is LF, down came the beams in favour of omni-directional antennas. Now that there are no beams to foul I have been able to place the fibreglass extension back on the top of the mast to secure the top of the LF vertical. July 2006 I have decided (at least until I have compared my efforts with the “Spiral Top Load” and traditional types of antenna) to erect a 2 parallel wire top load to my 12 metre vertical. The two wires will each have a separation of 1000 mm approximately and be about 16 metres long but due to the small garden area will be steeply sloping down 8 metres each side in a similar way to my earlier umbrella top-load. Various other lengths and arrangements were tried.
February 2007 Taking a leaf out of Mike’s (G3XDV) book I have now added a lightweight elevated inductance (375 uH) just under the top load wires using a 3 litre cider bottle (contents enjoyable). The main vertical section of the antenna is made up of 8 insulated stranded wires twisted together like Litz wire & the top centre spreader support is constructed from 3 mm copper wire which forms the top 1 metre of the vertical. This is suspended from the top of the vertical fibreglass pole using a large ribbed glass insulator & held away from the mast by about 1.5 metres with the horizontal fibreglass stand-off. The 2 top load wires are connected to the copper wire spreader & run parallel to each other to the end supports which are constructed from a 10 mm PVC tube, glass ribbed insulators & a 5 mm PVC tube inside to carry the wire and improve the strength whilst allowing the wire through the centre to move and maintain the parallel form. The final attachments are made with polypropylene rope from the insulators to a suitable anchoring point.
On the 21st February 2007 Ofcom announced that a limited number of SRPs (Special Research Permits) will be made available for 12 months from 1st March 2007 to operate on the frequency band 501.000 khz to 504.000 khz. March 2007 I made a late application & was granted a permit from the 8th March 2007 to 29th February 2008 using the modes A1A, F1B & G1B with a maximum ERP of -10 dbW (100mW). Work has now urgently been re-directed to constructing a transmitter and modifying the loading coil for the new frequency allocation.