[R-390] Collins Filters

[quartz55]

Does anyone have any direct information on the insertion loss of the mechanical filters. I have 2 pdf files from Collins, F455FA21 (Plastic type I think), and F455N-20, the standard R390A metal tube type.  Both list insertion loss at 25dB MAX.  Does anyone know what typical values are?  The 8K one I fixed has only 8 dB IL.  The 2K and 4K I repaired both are in the 25 dB area.  Both R390A's I have seem to produce more 'volume' when switching to 8/16K.  I'm going to pull the 16K today and see what it's like and then replace the foam in it.

I have some text with links to pics for the repairs I've done, as soon as I clean it up, I'll be posting it.  The pictures are already posted at PhotoBucket if anyone wants to look through them. http://s251.photobucket.com/user/DogTi/library/R390A/R390A%20Filter%20Repair?sort=2&page=1

Dave