Cheers, The answer to all your questions is yes, aditionally the coax I used was Teflon and I did not do any flexing of it as it was rather stiff, so I cannot answer that question. I also did a follow up on a further inquiry from Norm N5NPO which may provide more info.
Allan Crites WA9ZZU --- On Tue, 2/2/10, skipp025 <skipp...@yahoo.com> wrote: > From: skipp025 <skipp...@yahoo.com> > Subject: [Repeater-Builder] Re: Building a notch duplexer with notch cans. > To: Repeater-Builder@yahoogroups.com > Date: Tuesday, February 2, 2010, 11:02 AM > > > > > > > > > > > > > > > > > > > > > > > > > > > > > allan crites <wa9...@...> wrote: > > > Gentlemen: > > > For those wishing to convert a BP cavity to operate as > both > > > a BP and notch cavity there exists a simple and > convenient > > > way to do so with out having to do surgery on the > innards > > > of the cavity. > > > > We're all about simple and convenient.. . > > > > > One only needs two 1/2 WL of coax (must be double > shielded, > > > can be RG-214 but I prefer an equivalent Teflon type) > with > > > connectors on one end to mate with two Tee connectors, > one > > > on each of the input and output of the BP cavity, > > > > Each of the two cavity probe port SO-239 type coax fittings > gets > > a Tee screwed down onto it? Screwed onto one side of each > Tee > > is an approximately 1/2 WL coax line? > > > > > and a high quality variable capacitor of 1-15pF, > preferably > > > quartz. > > > The center conductors of the two open coax ends are > connected > > > in series with the variable capacitor. The shields of > the coax > > > must be securely connected together. I used a small > 1" square > > > of PCB material to solder the two shields together and > to > > > support the capacitor. Using Teflon coax makes this > much > > > easier. > > > > The entire loop through the variable capacitor back to the > other > > Tee is 1 wave length? > > > > > The 1/2 WL of each coax is measured from the center of > one > > > Tee adapter to the jct of the variable cap taking into > account > > > the VP of the coax. > > > > OK > > > > > The variable cap series resonates with the inductance > of the > > > two loop assemblies and can provide a notch on either > side > > > of the center of the BP cavity tuning, depending on > the > > > inductance of the loops. If you find the cap > adjustment not > > > enough then a higher value cap may be required. > > > > > The BP tuning is very broad and should be adjusted > first > > > for best return loss. > > > > Is there a relative comparison of the BP Tuning versus an > > unmodified/stock cavity? Based on your experience with the > > > suggested network are they similar? > > > > I would speculate the extra hardware does reduce the > circuit > > Q a bit. > > > > > Then the notch can be adjusted. Appropriate shielding > > > > should be provided around the variable cap and the > open > > > coax before using in the final configuration. > > > > Does the tuning change as the coax lines are flexed? > > > > > If you have any problems or questions I will be > willing to > > > help. Just ask. > > > Allan Crites WA9ZZU > > > > Is the new circuit configured into a duplexer then treated > as > > a BpBr Cavity? > > > > cheers, > > s. > > > > > > > > > > > > > > > > > > > > > > > > > >
