Thanks for all replies. First of all this is the first duplexer I'm building and I'm not a very experienced user of the spectrum analyzer/tracking generator so it is possible that I adjusted something wrong as some of you point out. I'll try if that makes a difference as soon as I can.
Furthermore the article WalterH posted is the correct one. As he says the author did not make correct quarter wavelength cables but he also designed it for 440-450MHz and I want to use it at 430-440MHz so I made cables that are one quarter wavelength from end of connector to end of connector with the velocity factor taken into account. I thought this wouldn't hurt but probably I'm wrong. I did hook the two cavities up directly, there's no antenna tee installed yet, therefore the other port is not connected at all. The main reason for this is that the other branch is not working yet. BTW. the passband is at -10 so the notch is only -52 actually, less than the author achieved. Regards Martin
