This Q-multiplied loop amplifies signals and nulls out electrical interference. Some of the readers who constructed the Active Ferrite Loop Aerial (Sept '00) have asked if its coverage can be extended to long waves and through the shortwave bands. Tuning to a lower wavelength presents no problems: simply increase the turns of wire on the loop to 144 for the main and three for the feedback winding. Use 38 s.w.g. (34 a.w.g.) enamelled wire arranged in four "pies" or piles of 36 turns to reduce self-capacity. Performance, in terms of signal output and depth of null, is very satisfactory at the lower frequency.

Extending coverage through the shortwave spectrum is not so easy. The performance of ferrite rods available to home-constructors deteriorates above 2MHz or 3MHz until, at around 10MHz, they are no longer of benefit. Moreover, the original loop was designed specifically for medium wave working and its efficiency and ease of operation diminish as frequency increases. A new circuit has, therefore, been developed for reception between 1·6MHz and 30MHz.