LF-30A Kenwood Low Pass Filter

Cut off Frequency 30MHz * Max att. 90dB (above 90MHz) Max power 1kW. Made by Kenwood, this low pass filter has proved ideal in suppressing harmonics from my HF transceiver operating up to 30MHz. The unit has been in production for quite a few years and is well respected by radio operators around the world.

Lee-Belling Mains RF Filter 16A 3 STAGE CHASSIS

Ultra high performance chassis mounting two stage mains RF filter with earth line choke provides excellent attenuation over a wide frequency range on all three mains lines. This superb device, used in conjunction with an equipotential ground plate, cured my mains borne TVI problems.

The function of a line filter is to permit the flow of supply currents in the range 0 to 400Hz and to prevent the flow of undesired frequencies which in general extend from 10KHz to 1GHz. This is achieved by adopting basic low pass filter configurations using shunt capacitors and series inductors to attenuate high frequencies. The low pass filter is effective in either direction and thus can be used to prevent excessive emissions from the equipment to the mains line and limit the flow of spurious signals into the equipment from the mains line.

Due to unknown parameters such as the source impedance of the unwanted signals, it may be difficult to predict the precise behaviour of a filter in any given equipment, hence direct measurements under standard conditions are made using prescribed procedures and apparatus to confirm the performance of an iec line filter. Resistors are incorporated into the filter for damping resonances as well as providing safety discharge paths and non-linear devices such as metal oxide varistors and zener diode combinations are used to deal with voltage transients. Suppression components may be required in the earth conductor as well as the current carrying conductors to achieve satisfactory performance.