Eric,
This sounds like an interdigital filter which is a cavity bandpass filter used in applications like ATV. They were made by a number of companies and many homebrewed.
They were a bandpass with wide pass and steep skirts for wide band signals like NTSC video in the 420 MHz range. Normally there was no notch, but with some miss tuning might obtain one or two.
Moving to 440 range might be a problem if designed for 420. 73, ron, n9ee/r Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome. On Thu, May 22, 2008 at 1:19 AM, kk2ed wrote: I have a Celwave filter PN 9182510Y17 MFG date of 2/4/00 It is about 10"x10" square and 1" high, and has SMA connectors, one on each side (left/right) , and 9 flat-head tuning screws in the front (just like the ones on the small 50w duplexers). It was brand new in the wrapper when I found it. I swept it on my tracking generator, and it looked to be some sort of window filter, centered at 390MHz or so. I attempted to retune it to the 444MHz range, as I need a filter in front of a preamp at a repeater site to clean up some interference from a T-Band system. I was able to retune it to provide a nice curve at 444MHz with about 2db insertion loss, and about 50db down at 460MHz. It also looks like it has one or two notches to the high side, so I could notch out a particular 470 frequency if needed. The strange thing (why I'm posting) is the tuning behavior. Of the nine tuning screws, counting them 1-9 from left to right, screws 1, 5, and 9 all seem to adjust the passband center freq, screws 3 and 7 seem to adjust what appears to be two notches (or one if I "pull" them together), and screws 2,4,6, and 8 seem to do nothing at all. Anyone have any ideas as to exactly what kind of filter this thing is, and how to properly tune it? As it stands right now, based on how it plots on my 8920's tracking generator, it looks like it should make a halfway decent filter for in front of a preamp, but I'd like to tune it properly if I can figure out how and what kind of filter it was designed to be. Thanks Eric KE2D
