[CQ-Contest] 419A Bandpass Filter - Value?

[Jim Brown]

On 2/20/2021 10:29 AM, Mark n2qt wrote:
> Replacing the micas with Cornell Dubilier CDV style micas helps as those parts
> have better specs for RF.  I ran rtty contests at 100 watts with no subsequent failures.
> (My problem was always on 15)

The problem with changing or replacing parts in this filter set is that 
1) it's very hard to take apart to replace the parts and 2) each filter 
in which parts are replaced must be re-aligned with good 
instrumentation, AND measurements must made with the enclosure in place 
because it affects the filter's tuning. So in practice, you've got to 
measure, tweak one or more coils by squeezing or spreading them, put it 
back in the enclosure to measure again, repeat, repeat, repeat, repeat 
until you get the SWR and transmission loss VERY low in the passband.

The Dunestar filter sets, and the higher priced units that WX0B sells 
are FAR superior. The high power VA6AM and 4O3A filters designed to go 
on power amp outputs are also excellent.

73, Jim K9YC