Since your post I've been googling like hell and found one Dutch design of a copper clad duplexer by PA0NHC, but this also has two loops per cavity and uses 8 cavities. However it answers the question about square enclosures and could be a reference design.
Furthermore I found a design by WB3AYW which uses 16 gallon transmission fluid barrels as cavities in BPBR configuration using 4 cavities. This one looks easy to build and is somewhat similar to the beer keg duplexer which has been made professionally in the seventies afaik. The problem with these is that a 4 cavity duplexer gets pretty big and will hardly fit into a 19" cabinet. Does anyone know of any other particular homebrew design, especially one which uses some kind of available enclosure similar to the barrels but more space-saving? I also found some notice that the heliax duplexer, which is well-known for 6 meters, could also be built for 2 meters, but no detailed info was given. If anyone knows more about this, please tell... --- In [email protected], DCFluX <dcf...@...> wrote: > > There were a couple of designs that used copper circuit boards to form > square boxes for the outer jacket of the duplexer. > > Size maters as the inner to outer diameter ratio effects the impedance > of the cavity. It is my understanding that the optimum impedance for > a cavity is approx 70 ohms. Not sure if this is true for cavities, but > with helical resonators square shields have higher Q than round ones. > > You would also probably be better off using a BpBr style design, as I > remember W1GANs was for pass cavities which would require 6, BpBr can > get away with use 4, they would be similar but only have 1 coupling > loop that has a high quality trimmer capacitor such as a johansen or a > coaxial gimmic in the ground leg of the loop to set the notch > frequency. > > On Fri, Apr 24, 2009 at 4:19 AM, cruizzer77 <atlant...@...> wrote: > > Hi > > > > Most of you who are into duplexers will know W1GAN's old QST-article "A > > Homemade Duplexer for 2-Meter Repeaters". > > > > His design uses 4" copper tubes, but today many duplexer manufacturers use > > square aluminium profile as duplexer bodies, i.e. Sinclair but others as > > well. Now I wondered if W1GAN's design could be used for building such an > > aluminium square tube duplexer as well and if it would work equally well. > > Does anybody know? > > > > Instead of the 4" round tube, would a 4" square tube be used, or does the > > circumference matter? > > > > Kind regards > > > > Martin > > > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > >
