"Duplexer" is a generic term for a filter network that allows a single antenna to be used for a receiver and transmitter in the same band, such as a repeater. These usually take the form of several cavity resonators, coaxial stubs or even helical resonators in either a band pass, notch reject or band pass band reject.
A single cavity may be added between the duplexer and receiver if there is alot of RF at the site and or the duplexer offers very little out of band attenuation, But the cavity has to be a low enough quality to have a pass band wide enough for both the transmit and receive frequencies. "Diplexer" is a filter network that facilitates a single antenna to be used on 2,3 or 4 different bands, either feeding a single radio or multiple radios. Usually constructed with L/C filter networks. A "Combiner" is a device which allows several transmitters, very close in frequency to use a single antenna. These are usually a dual stage circulator followed by large band pass cavitiy per channel into a passive power divider with enough ports to handle the total number of channels A "Circulator" is essentially a one way valve that allows RF to pass in one direction. Used in combiners and for intermod control to keep transmitters from mixing stray RF. Power refelected back from the antenna goes into a dummy load instead of the transmitter. On Sun, Oct 25, 2009 at 8:14 PM, Marcus <[email protected]> wrote: > > > thats fine, but unless i am mistaken, a Duplexor is not a cavity filter > > the duplexor is installed before the cavity filter(S) the output of the > cavity filter(S) goes to the Aerial > > > Marcus > > > K5IN wrote: > > > > I listed Decibel products DB-4071 duplexers a couple of days ago for > $150.00 shipped. > > Brian, [email protected] > > ----- Original Message ----- > *From:* Marcus <[email protected]> > *To:* [email protected] > *Sent:* Sunday, October 25, 2009 5:30 PM > *Subject:* [Repeater-Builder] Tait UHF Standby Repeater D-Band > > > > is there anyone on this list that resides in NZ and if so/not does > anyone have any Cavity filters, if so how much > i have a Tait Repeater running D-BAND it was a backup system > > would like to get it running, forgive the contradiction, the system is > fully operational, i would like to put it to some use > > must be loads of points i have not mentioned, so if need be fire away, i > shall answer all my old almost had it brain can conjur up > > Marcus > > > >
