rabinal
antenna tuning and feed
080815 {yymmdd}
This is a multi-band antenna, 15, 21, 28 MHz and possibly more. It is horizontally polarised; the end verticals are put there as "top hat" capacitative loaders to keep the average current up in the radiating horizontal part of the antenna. Because the wavelength at 15 MHz is 20 metres, and this antenna structure is only 4 metres long, it needs to be tuned inductively to form a match. This also means that is is high-Q, narrow bandwidth, and that the tuning is critical within the amateur bands. It managed a QSO from Guildford, Surrey, UK to a lighthouse keeper in Germany, for very little effort indeed, even though the antenna elements are only at head height, beneath an overlooking hill.
see
antenna tuning and feed
080815 {yymmdd}
This is a multi-band antenna, 15, 21, 28 MHz and possibly more. It is horizontally polarised; the end verticals are put there as "top hat" capacitative loaders to keep the average current up in the radiating horizontal part of the antenna. Because the wavelength at 15 MHz is 20 metres, and this antenna structure is only 4 metres long, it needs to be tuned inductively to form a match. This also means that is is high-Q, narrow bandwidth, and that the tuning is critical within the amateur bands. It managed a QSO from Guildford, Surrey, UK to a lighthouse keeper in Germany, for very little effort indeed, even though the antenna elements are only at head height, beneath an overlooking hill.
see