That would be the design I was thinking of, You would only build half of the enclosure in a 1x4 configuration. To convert to BpBr you would only have one coupling loop per cavity and on the ground leg of the loop you would have a high quality variable capacitor or a N or BNC connector to come out to a gimmic style capacitor like the Wacom cavities use.
Sinclair has some VHF and 220 duplexers that are rack mount friendly made of aluminum extrusions which could be used for a size reference. I would think 4" square inner dimension and .125 or .25 thick walls. Aerial facilities limited was the company that made the beer keg cavities. See: http://www.ingenia.org.uk/ingenia/issues/issue18/david.pdf They also produced a 8" or so band pass cavity that was rack mount friendly, I converted 4 of these from an ACSSB combiner to be a BpBr duplexer by removing the one loop and adding a johansen capacitor and cutting RG-214 coax the right length. got about -1.4dB loss and -84 dB rejection per leg On Sun, Apr 26, 2009 at 1:03 PM, cruizzer77 <[email protected]> wrote: > 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... > >
