My extensive response to your question was deleted by my computer before I could send it. Bummer. I will try again tomorrow. Allan Crites WA9ZZU
--- On Mon, 2/1/10, NORM KNAPP <[email protected]> wrote: > From: NORM KNAPP <[email protected]> > Subject: Re: [Repeater-Builder] Re: Building a notch duplexer with notch cans. > To: [email protected] > Date: Monday, February 1, 2010, 2:04 PM > > > > > > > > > > > > > > > > > > > > > > > > > > Why would it need to be a full wave length at pass > frequency (or would that be reject) with a capacitor in > series? Shouldn't that be a half with cap splitting the > middle? > > > Thanks! > > > 73 de N5NPO > > > Norm > > > > > > ----- Original Message ----- > > > From: Repeater-Builder@ > yahoogroups. com <Repeater-Builder@ > yahoogroups. com> > > > To: Repeater-Builder@ > yahoogroups. com <Repeater-Builder@ > yahoogroups. com> > > > Sent: Mon Feb 01 10:20:59 2010 > > > Subject: Re: [Repeater-Builder] Re: Building a notch > duplexer with notch cans. > > > > > > > > > > > > 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. > > > 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, 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 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. > > > 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. 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. > > > If you have any problems or questions I will be willing to > help. Just ask. > > > > > > Allan Crites WA9ZZU > > > > > > --- On Mon, 2/1/10, NORM KNAPP <nkn...@twowayradio. > net <mailto:nknapp% 40twowayradio. net> > > wrote: > > > > > > > From: NORM KNAPP <nkn...@twowayradio. > net <mailto:nknapp% 40twowayradio. net> > > > > > Subject: Re: [Repeater-Builder] Re: Building a notch > duplexer with notch cans. > > > > To: Repeater-Builder@ > yahoogroups. com <mailto:Repeater- Builder%40yahoog > roups.com> > > > > Date: Monday, February 1, 2010, 8:53 AM > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I am also experimenting with some 8" DB > > > > Products band-pass cans from a combiner network. I > took a > > > > coupling loop assembly from a Telewave TPRD series > duplexer > > > > and tried in one. It works great! I would imagine the > TPRD > > > > harness would be correct because of the loops. I sent > an > > > > e-mail to telewave about buying some loop assemblies, > but > > > > haven't heard back yet. I may try building some to > try. > > > > > > > > > > > > Keep us posted on your findings. > > > > > > > > > > > > 73 de N5NPO > > > > > > > > > > > > Norm > > > > > > > > > > > > > > > > > > > > > > > > ----- Original Message ----- > > > > > > > > > > > > From: Repeater-Builder@ > > > > yahoogroups. com <Repeater-Builder@ > > > > yahoogroups. com> > > > > > > > > > > > > To: Repeater-Builder@ > > > > yahoogroups. com <Repeater-Builder@ > > > > yahoogroups. com> > > > > > > > > > > > > Sent: Mon Feb 01 07:46:16 2010 > > > > > > > > > > > > Subject: [Repeater-Builder] Re: Building a notch > duplexer > > > > with notch cans. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --- In Repeater-Builder@ > > > > yahoogroups. com <mailto:Repeater- Builder%40yahoog > > > > roups.com> , "skipp025" <skipp...@.. > .> > > > > wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > Re: Building a notch duplexer with notch cans. > > > > > > > > > > > > > > > > > > > > > > > > > > You would not be restricted to using > DB/Andrew/DB- > > > > Spectra loops > > > > > > > > > > > > > if the proper type and size were available from > > > > another source. > > > > > > > > > > > > > Regardless, the price is probably going to be > over > > > > $200 minimum > > > > > > > > > > > > > for a 4 cavity probe kit and matching coax > harness. I > > > > would actually > > > > > > > > > > > > > expect more... > > > > > > > > > > > > > > > > > > > > > > > > I am curious if andrew still support the DB line of > filter > > > > (next thing on my list of things to inquire about) > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > we have 4 pass cans at the site in a cabinet > that > > > > are just > > > > > > > > > > > > > > waiting to have some vari caps installed to > make > > > > them into > > > > > > > > > > > > > > pass/reject cans. > > > > > > > > > > > > > > > > > > > > > > > > > > The free lunch you think you're going to get > by > > > > simply installing > > > > > > > > > > > > > the small piston caps in series with the cavity > loops > > > > is in > > > > > > > > > > > > > my opinion fairly optimistic. > > > > > > > > > > > > > > > > > > > > > > > > I dont think it would be a free lunch, even 10 to 15 > db > > > > notch on a pass can it still workable, but i am open > for > > > > your thoughts on the subject. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > as far as making these into pass/reject, i > am not > > > > sure how > > > > > > > > > > > > > > you modify the loops. Unless you can add a > vari > > > > cap on the > > > > > > > > > > > > > > ground side of the loop. > > > > > > > > > > > > > > > > > > > > > > > > > > That's the trick a lot of people are saying > will > > > > work. It's not > > > > > > > > > > > > > the type of loop/probe I use or make (mine are > > > > constructed more > > > > > > > > > > > > > like the Telewave TPRD type) but they may work. > The > > > > Repeater Builder > > > > > > > > > > > > > Web Site has information about how Hams have > modified > > > > cavity > > > > > > > > > > > > > probes from Band-Pass to Band-Pass, Band-Reject > with > > > > reportedly > > > > > > > > > > > > > decent performance and cost savings. > > > > > > > > > > > > > > > > > > > > > > > > > > If you're going to be constructing BpBr > Probes, I > > > > would suggest > > > > > > > > > > > > > you make new cavity port probes rather than > modifying > > > > the > > > > > > > > > > > > > originals. > > > > > > > > > > > > > > > > > > > > > > > > > > The materials and parts shouldn't be that > exotic > > > > or hard to find > > > > > > > > > > > > > unless you live well away from a decent size > city... > > > > or lose > > > > > > > > > > > > > access to the web/internet and the Post Office. > > > > > > > > > > > > > > > > > > > > > > > > > > s. > > > > > > > > > > > > > > > > > > > > > > > > > Ok i will look through the website and see what i can > find. > > > > I have an old FM/repeater manual from several years > ago, and > > > > the arrl antenna book, both provide construction > articles > > > > and i will look at the loops that they recommend > building > > > > also. > > > > > > > > > > > > > > > > > > > > > > > > I believe the 2 ways i have seen the loops modified > are: > > > > > > > > > > > > > > > > > > > > > > > > 1) vari cap between the loops of a pass can. > > > > > > > > > > > > > > > > > > > > > > > > 2) veri cap inserted in the ground end of the loops of > a > > > > pass can. > > > > > > > > > > > > > > > > > > > > > > > > are there any others? > > > > > > > > > > > > > > > > > > > > > > > > By the way, i appreciate all the suggestions. thank > you to > > > > all that have responded. > > > > > > > > > > > > > > > > > > > > > > > > de kd4wov Tom > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
