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Homebrew Amateur Radio 440Mhz Interdigital Bandpass Filter
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The shell of these UHF Bandpass Interdigital filters are made out of double sided copper printed circuit boards. The rods are 1/4 copper refrigeration tubing. The tuning is done with 3/32 brass screws or similar. You need to tune these with a sweep generator or spectrum analyzer. They work very well at removing commercial transmitter interference above the ham bands. Bandwidth on mine were about 3 mhz with less than 2 db loss. You can make up for the loss with a UHF Preamplifier.

Inside view of a UHF Interdigital Filter

Completed UHF Interdigital Filter