A description and picture featuring the massive loading coil I use with my Marconi antenna for 136KHz, have recently appeared in RadCom, the monthly magazine of the Radio Society of Great Britain, RSGB, December 2009, page 29. ( click on the post title to visit the RSGB web site ).
The main winding consists of about 400 turns on a 15cm diameter, 108cm long, sewer pipe and has multiple tapping points. The rotatable variometer winding inside is made from 37 turns on a 11cm diameter plastic water-pipe. The upturned plastic food container on top keeps water out.
The impedance matching network to the 50 Ohm coaxial cable feeder from the transmitter uses an ETD44 transformer core with a 9 turn primary winding and a 20 turn secondary winding. I can obtain a perfect match with this method, though occasionally there is slight detuning of the antenna system owing to environmental effects, requiring readjustment of the variometer.
