More on bandpass filters

A bandpass filler is designed to pass all frequencies thai i\re above a lower rutoff frequency and all frequencies that are below an upper cutoff frequency. Figures and 23-15 show two approaches to making a bandpass filter for the high-frequency (HF) shortwave bands. The cir cuit in Pig 23-14 is designed for a frequency I »and of 2 to 33 MHz, so il will encompass the entire HF short wave band while eliminating interference from LF and MW AM band broadt/asters as well as VHF stations. Notice that each section is built inside its own shielded < omparlinent. This is good layout practice for any multisection filter and it prevents interaction between the elements (especially coils).

The bandpass filter in Fig. 23-15 is not so elegant as the previous example but it serves the purpose. This approach to bandpass filter design cascades low-pas* and high-pass sections. The input side of Fig. 23-15 is ihe AM BCB filler used in the las I paragraph and the output section is a -MHz low-pass filter of similar design.

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2J-J5 A 2- t<> 33-MHz Uintipais filler • i»■ raw-adin^ tow-iuss arni hi£li-| ww m-' liotis.

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