That is true for band pass filters but in the case of a duplexer the filters are usually notch type (or pass/notch). So the more notch type cans there are the wider the notch will be at some given frequency. Think of it as an upside down band pass response.
Note that the pass response of a band pass / reject type duplexer is very wide to start with. 73 Gary K4FMX _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Brown Sent: Friday, June 27, 2008 4:32 PM To: [email protected] Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune duplexer? Doug, It has always been my experience that adding two or more cans in series always narrows the bandpass, not widen it. The first can will show a given dB down at x frequency away from the center tune. Adding the second can will decrease the level by the sum of the two at the same x frequency from the center tune. The more bandpass cans you use in series, the narrower the bandpass. 73 - Jim W5ZIT --- On Fri, 6/27/08, Doug Bade <[EMAIL PROTECTED]> wrote: From: Doug Bade <[EMAIL PROTECTED]> Subject: Re: [Repeater-Builder] Re: Frequency Change do I retune duplexer? To: [email protected] Date: Friday, June 27, 2008, 11:22 AM 4 cans winds up in mhz wide as apposed to khz wide... ( as in an rx preselector, the more cans the wider it is....) Doug KD8B __
