[R-390] Vol 28, Issue 3: Dave Curry R-390A filters

[Flowertime01 at wmconnect.com]

Charlie

I think your input is a good as we can get. 

Craig, will know he has enough capacitance when the trim cap provides a 
double peak. One peak on each side of the cap maximum. If capacitance is added in 
small step so as not to over run the variable cap range. 

A trimmer cap could be tried in the circuit to find the correct range.

Earlier this year one of the Fellows ran a sweep generator across the 
mechanical filters and provided picture for all to look at. The thing we learned from 
that was the trimmer cap provides a match that reduces or increases insertion 
loss. The cap matching has no effect ("OK very little effect") band pass.

A couple of the caps just keep DC off the filter coils. 

Craig, should be able to get the filter soldered in with little problem.
Watch the DC isolation and use those caps.
Keep the trim caps in (both ends if existing) [Side chassis and top of filter]

Check the signal level compared to the other filters. 
If the Curry filter has lower signal level than the other filters then start 
adding larger value coupling caps to the Curry filter.

Alternative is to trim the caps on the other filters back to give equal pass 
on all filters and then reset the DC gain adjust.

Roger AI4NI