Band pass filters for HF

Bandpass filters are used to effectively suppress strong signals outside the respective band. This reduces noise in the band, produces fewer unwanted mixing products, and makes it easier to hear weak signals. During transmission, any by-products are effectively suppressed and thus disturb the immediately adjacent stations less. The 160m high-pass filter suppresses everything below 1700 kHz (medium and long wave) and thus relieves the receiver input of strong radio signals.

Band passes are often used for contest stations in multi/multi or multi/2 operation, but also for stations with only one operator and two stations (SO2R) such filters are a good investment. The bandpass filters are manufactured with high quality ceramic capacitors to keep insertion losses as low as possible. Moreover, these capacitors allow a higher load during transmission, the filters can be used with a power of up to 1000W PEP (500W CW).

The filters have PL sockets and are looped into the antenna cable with a short coaxial cable directly behind the power amplifier and in front of the antenna. Impedance 50 Ω, housing size 115 x 64 x 56 mm including sockets. The filters are housed in a waterproof case (IP66 standard) and can therefore also be used on a fieldday or other occasions where there is a risk that they get wet. To prevent internal condensation, an air pressure valve has been installed in the housing. This valve keeps the air pressure inside the housing equal to the air pressure outside the housing.

This valve must not be removed.

The Competition versions of the band filters (available for 20 and 40m) have significantly steeper flanks, i.e. better damping outside the pass band. This is very helpful in situations where, for example, contest stations are close together.