[R-390] Filter repair

[quartz55]

Good news.  I tested the repaired 4K filter and here is the response on my test set. It measures right at 4KHz at 6db down, if a bit shifted up in freq (50Hz). The 2K is the shifted down about the same. I think that's pretty irrelevent.

http://i251.photobucket.com/albums/gg287/DogTi/R390A/4Krepairedfilter_zps3cae2037.jpg

My generator (SM) only has 100Hz steps, so right now or until I build a VFO, I'm kind of locked into using it.  I've been using my test setup with a 2K FA type I repaired and it appears to be very consistent as far as the nose response.  I can only get about 30db range with my test set.  I'm working on extending the range, and that will come. Given the sharp drop of the skirts, I don't expect the filters not to have enough ultimate rejection or be out of spec.  The repaired 2K FA filter appears to have about 16 db loss, the spec on it is 9 db. I don't understand that unless I'm mistaken.  The repaired R390A 4K filter has a loss of 0.3V to .022V or 22.6db, well within reason as far as I'm concerned.  Now we'll see if it lasts.

Just amazing, I really didn't expect this to work. I'm going to cut off the studs of the FA filters and put it in the R390A 2K tube.

I suppose I should build up a high voltage isolation tester while I'm at it.

Dave
N3DT