I don't think any of them have cavities in them. I would suspect that the telewave is built very similar to the diamond etc. Mostly lumped circuit tuning (capacitor and coils) and maybe some 1/4 wave stub tuned coax rolled up inside.
For a long time most commercial manufactures like telewave Sinclair etc. stayed away from cross band couplers between 150 and 450 bands but readily did it between 800 and 450 or 800 and 150. The problem with 150 and 450 is that they are harmonically related. A quarter wave length cavity on 150 is a three quarter wave length cavity on 450. A three quarter wave cavity resonates just as well at three quarter wave as it does at a quarter wave but of course has more selectivity as a three quarter wave. Most of the better transmitter combiners for 800 and 900 MHz used three quarter wave length cavities in them. Most of the cross band couplers use capacitors and inductors to form low and high pass filters to get around the 3rd resonance mode of cavities. Cross band couplers open the door for intermode problems as those 3rd harmonics are not attenuated all that much in the couplers. They do work but sometimes may cause problems. DUPLEXER / DIPLEXER A duplexer and diplexer are very similar. A diplexer is what it is usually called when two transmitters are combined together. If a transmitter and receiver are combined then it is called a duplexer. The cross band couplers I suppose could be called either as they do combine two transmitters but they also combine two receivers and allow duplex operation. You could have a 450 receiver working at the same time as a 150 transmitter so that would be a duplex situation. Maybe they should be called duo-duplexers. :>) 73 Gary K4FMX > -----Original Message----- > From: Repeater-Builder@yahoogroups.com [mailto:Repeater- > [EMAIL PROTECTED] On Behalf Of crackedofn0de > Sent: Friday, April 27, 2007 9:34 AM > To: Repeater-Builder@yahoogroups.com > Subject: [Repeater-Builder] Re: Repeater Antenna Question > > --- In Repeater-Builder@yahoogroups.com, [EMAIL PROTECTED] wrote: > > > > In a message dated 4/26/2007 4:39:57 P.M. Eastern Daylight Time, > > [EMAIL PROTECTED] writes: > > > > cross band coupler > > > > > > Thanks that sounds like the ticket..... Seems like the way to go > > > > > > JA > > How about a diplexer from Comet or Diamond? I looked into this > recently for a similar application and couldn't tell the difference > between the expensive Telewave crossband couplers and the dime-a-dozen > amateur diplexers. The specs given for the diplexers even indicate > about twice the isolation compared to the crossband couplers. While > the designs appear to be different (tuned "cavity" vs. tuned circuit), > I can't find any information that would indicate any pros or cons > between the two in practice. Anybody? > > Both Comet and Diamond call their diplexers duplexers. I have no idea > why. They get it right when they call their triplexers triplexers. > > I was thinking about going with a Diamond product (they at least have > a metal housing) and swapping out any UHF connectors for N types. > > http://www.rfparts.com/diamond/Product_Catalog/plexers.html > > http://www.cometantenna.com/products.php?CatID=1&famID=6&childID=0 > > > > > > > > > Yahoo! Groups Links > > >
