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