Re: 6 metre 4 pole filter
Starts getting a bit big on 6 metres... about 1 metre long each assuming 69% velocity factor for PTFE dielectric 'semi-rigid coax'
But quarter-lambda lines are rather useful for narrowband filters. For 70MHz in a small space, helical resonators are a good possibility. You can get SAW filters covering various ranges around that frequency... see Golledge's website. But the insertion loss of SAWs can be off-putting.
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
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