Don, I don¡¯t have enough information from you, so let me ask you to do this:
Attach the four bypass networks to stages 2,3,4, and 5. Set the RBW to 1 kHz. This will leave only the first stage filter in the path. You should see a filter shape with skirts that go down perhaps 25 dB on either side. (Set the span wide enough, so you can see the filter skirts that far down.) The 3dB bandwidth will be around 2.3 kHz, I think.
What happens when you try to adjust the SYM capacitor in stage 1? Does it run out of range and it can never make the skirts reasonably symmetrical? Does it work well and you can adjust for symmetrical skirts? There is some interaction between the SYM and CTR adjustments, so iterate between the two until it looks like you have optimized both.
If you can adjust the first stage so the notch is gone, move the bypass network from the second stage to the first stage and repeat what you just did, this time on the second stage. This time, stages 1,3,4, and 5 will be bypassed and you will be observing? the second stage only.
You cannot adjust this filter correctly if you have more than one stage in the signal path.
Do this until you have checked all 5 stages. This should help you narrow down the problem to one stage.
Also, can you post a picture?
Vladan
