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Making a broadcast filter for 160m.
Transmit RF bypass design.

This project involved the construction of a broadcast rejection filter, suitable for continuous inline use, on the 160m amateur radio band, that can handle the full output rf current of a 100 watt amateur transceiver.
The schematic on the lid shows the values I have used in this particular filter's construction, as opposed to the optimised circuit design values shown below. One added feature is that the antenna connection is dc grounded via L5, which helps bleed off static build-up on long wire antennae. This circuit is quite successful.
 
 
Finished filter project
 
 
What's in the box.

Here is an inside view of the filter with the cover removed. I've used a mixture of silver mica and ceramic capacitors. The ratings of 500 volt or more, means the plate area is likely to be large, to handle the larger rf currents when used with higher power transceivers. The capacitor combinations may vary, depending on what may be available to you. The parts are "fixed" with hot melt glue, to prevent possible failure due to vibration or shock movement.
Also note, that the inductors are wound such that the actual windings are circular, to help improve their "Q".

 
 
BC Filter - inside view
 
 
Circuit layout.

The schematic shows an optimised design produced by Paul, VK5AB. Thanks Paul. This circuit is designed to give more than 40dB rejection of broadcast stations in the AM broadcast frequency range. The final component values can be re-checked with the freely available software mentioned on a previous page and any variations can also be determined with the substitution of actual components/combinations that you may have. Hope you have similar success.

 
 
Schematic of optimised BC filter
 
       
    2006 - 2009 S.Spirat 
Another SPIRAT initiative