> -----Original Message----- > From: [email protected] [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of Ken Arck > Sent: Thursday, January 17, 2008 7:11 PM > To: [email protected] > Subject: Re: [Repeater-Builder] Re: MSR2000 transmit spike > > At 04:06 PM 1/17/2008, you wrote: > > > >This sort of thing happens a lot when people do a tweak peak > >adjustment of an already working transmitter/exciter. Some > >stages are by default properly aligned first for a meter dip > >indication while others are peaked. > > <--I'm still wondering how a low level signal 14 megs away from the > passband of a duplexer (assuming it's a Bp/Br) can radiate any distance. > > Ken
There is a lot of misunderstanding of Bp/Br duplexers. Just because it has the word "band pass" in the title doesn't mean that it is a good band pass device. If you look at the curves of most Bp/Br duplexers you will see that between the notch frequencies there is excellent band pass rejection because of the cumulative skirts of the filters in both sides of the duplexer in this area. However when you get on the outside of the notches there is little band pass effect and it is usually quite broad in respect to a true band pass filter. Also the ultimate rejection trails off too in most cases as you move farther away in frequency. As far as interference goes, either incoming or outgoing, it is all a matter of how much attenuation the filter devices are providing. As a note that may come in handy for someone chasing interference, you can use a pass band cavity as a notch cavity by just putting a T connector on one side and inserting it in line. Leave the other connection to the other loop blank. 73 Gary K4FMX
