Ferrite Loop Aerial For The 40 Metres Band

18 FERRITE LOOP AERIAL FOR THE 40 METRES BAND R.Q. Marris G2BZQ The ferrite rod aerial is typically associated with MW/LW radios, but it can be used on HF as well. Following a number of experiments with ferrite rod aerials, this article describes a highly directive type that covers the frequency range from 5,000 to about 8,300 kHz, spanning the popular 40 metres amateur band. The ferrite rod aerial found in MW /LW radios is usually made of a manganese- zinc material. The aerial described here uses a different material, a nickel-zinc alloy, and has a diameter of 0.5 inch. It can have a length of 7.5 inch, or 15 inch if two rods are glued end to end. The main purpose of using a ferrite rod aerial is to exploit its directivity to sup- press interference. To obtain the best possible Q (quality) factor, the inductance must be wound at either side of the rod centre. Also, the spacing between the turns and, most importantly, between the turns and the core, contribute to the selec- tivity...