I obtained a pair of DB4018-2 cavities (300-400 mHz on the nameplate) at a
hamfest and finally tore into them to see if I could make something worthwhile
in the way of frequency coverage out of them. Tests showed that they barely
made it up to 400 mHz on the high end, so I disassembled them and found a 2
inch brass washer brazed to the bottom end of the plunger. (all parts were
silver plated)
I removed the washer with a Dremel tool and reassembled them and found that
they both tuned just barely above 450 mHz after the mod. I did not check the
bottom end of the coverage but I am sure it would be somewhere below 400 mHz.
It was not necessary to remove the top of the can, just the bottom, as the
plunger screwed all the way to the bottom presents the washer for removal.
I thought I would pass this along in case any more of these beasts are around.
73 - Jim W5ZIT
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