It is not possible to get a notch that is 8 MHz wide. What you probably have is a pass band filter.
It sounds like you have what is called a "duplexer" for an 800 MHz trunking system. The "duplexer" is usually a set of 4 or 6 cavities set up as a wide band pass filter for the receive side. The transmit side would be a transmitter combiner with an isolator and a single band pass cavity for each transmitter. The output of the transmitter band pass cavities would feed a star junction to combine them all. The star junction for the transmitters would then connect to a T connector with one side of the T going to the antenna and the other side of the T going to the receiver band pass filter. There are other methods of combining also but this was the most popular. Trunk systems often used separate antennas for transmit and receive. The transmitters were most always combined as above and the output of the star junction would feed an antenna directly. That package was referred to as a "transmitter combiner". If the receivers were to be operated on the same antenna then the "duplexer" was added as described above. The "duplexer" in this system was just the multi cavity receive band pass filter. The cavities are "stager tuned" (each cavity tuned to a different frequency) to achieve the desired band pass. The band pass filter can be tuned with a signal generator and a signal detector by several settings of the generator to measure the frequency width and flatness of the band pass while tuning but it is very difficult to do. Tuning is best done with a tracking generator with frequency markers in order to tune the band pass to the proper frequency band and least attenuation over the pass band. If you have a different type system then maybe you could describe what you have. Regards Gary _____ From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of vikas gupta Sent: Tuesday, January 30, 2007 2:33 AM To: [email protected] Subject: Re: [Repeater-Builder] Re: 820 MHz duplexer problem:urgent !! the capacitor is ceramic type. can you please give me the construction detail of this type of duplexer. please give me. waiting for you. skipp025 <[EMAIL PROTECTED]> wrote: What type of material is the capacitor made from? skipp > vikas gupta [EMAIL PROTECTED]> wrote: > please advise me how i tune the duplexr of Tx (811.1-819.2MHz) Rx > (856.1-864.2 MHz) . I am tuning this by desigig band reject notch > type duplxer but I have a problem in achieving 1 dB insertin loss > and 70 dB iisolation on low and high side. > I am using 1 PF capacitor on high side . > > please suggest me how I design the duplexer and get 8 MHz broad notch. saparetion between Tx and Rx is 45 MHz. > _____ Have a burning question? Go to Yahoo! <http://answers.yahoo.com/;_ylc=X3oDMTFvbGNhMGE3BF9TAzM5NjU0NTEwOARfcwMzOTY1 NDUxMDMEc2VjA21haWxfdGFnbGluZQRzbGsDbWFpbF90YWcx> Answers and get answers from real people who know.
