That is poor engineering practice. On any site with multiple transmitters you must use a Circulator and Low pass filter to prevent mixing in the amplifier stages. What you have happening is that the possible IM products that fall within the passband of the amplifier stages are being amplified and probably are causing your own interference.
If you go to any website for a combiner company (TX/RX for example), you will see that on a TX combiner system you will have an Isolator/Circulator on the output of each transmitter, then fed to at least one 1/4 wave pass cavity and in most cases a two 3/4 wave cavities. Gregg R. Lengling, W9DHI, Retired Administrator http://www.milwaukeehdtv.org K2/100 S#3075 KX1 S# 57 Member: ARRL, RSGB, RCA, WERA and ORC -----Original Message----- From: lcradio2002 [mailto:[EMAIL PROTECTED] Sent: Monday, August 02, 2004 8:07 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] Seperate TX / RX antenna questions... Group, I have 3 UHF repeaters (TKR850) at one site, and one is getting some inteference. The system has a single, top mounted (60') DB420 feeding a RX multicoupler (Sinclair with a window filter). From there it goes to each repeater receiver. On the TX side, each repeater has it's own antenna, a DB408D (there are two TX antenna at about the 20' level, antennas are about 6' apart horizontally). I tried running without any cavities or duplexers, and it worked OK, but one receiver would get hit and key up. I put a single duplexer can in the RX path and it helped a lot. My question has to do with the type of cavity filter to use. I have some of the MOT square duplexers lying around (BPBR), and some 8" diameter TXRX cavities (BP only). In a system like this, which is normally used? Is it normal to put the cavity on the RX side only, TX side only, or both sides? I have never seen a multicoupler / seperate TX antenna system up close, so I dont know what is normally done in industry. Thanks, Tracy Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
