Kevin, This is an excellent question, and it should generate many responses.
The correct answer depends on several variables. It makes a difference if your cavities are strictly bandpass, strictly notch, or pseudo-bandpass/notch. The difference between these types is mainly in the coupling loop geometries, and whether the ends of the loops are grounded, or are tuned with a variable capacitor. The intuitive answer is that the impedance is the same at both ends of a half-wave length of cable, and is opposite at both ends of a quarter-wave length of cable. If I were connecting two bandpass cavities in series, I would expect that the jumper cable must be a half wavelength long, minus the lengths of the coupling loops themselves, and the connectors. The coupling loops are in air, while the cable velocity factor must be considered. Ah, but reality is not quite so simple! The degree of coupling by the loops at both ends of the jumper cable affects the phasing, and therefore the length, of the jumper cable. So, there is no simple answer. As much as I'd like to tell you to cut the jumper cables to xx centimeters each, I cannot. Since you do know the manufacturer and the model number of your cavities, I suggest that you contact that manufacturer's tech support, and ask for the dimensions of the cables needed to make the cavities work properly as a duplexer. You may learn that the coupling loops in one or more of your cavities must be changed to achieve this goal. 73, Eric Lemmon WB6FLY Kevin & Natalia Mitchell wrote: > > Hi All, > > I have just built a new set of 6x filters into a duplexer on 2m. > The problem I now have is what length do I make the interconnecting cables > between each filter, and then the output cables to feed 1x antenna. > I have read some information on this subject, however they do not appear to > agree with each other. One says a 1/4 wave of the freq. required for the > interconnect, another says any length, in multiplies of 1/4 wave. And for > the output/input, it says 1 length a 1/4 wave to a "TEE" with the other 1/2 > wave, and again another piece of information says both the same length to > the "TEE". > > If I could get the correct information, I will build the 2m duplexer, then > maybe look at building some UHF filters as well. > > BTW, filters are commercially made by Deltec, a NZ based firm. > > Regards > > Kevin, ZL1UDD. > > > > 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/ 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/
