The Duplexer will provide a specified amount of isolation. It has nothing to do with what you connect to it. It doesn't matter if it's a Spectrum transmitter of a GE MASTR II 110 watt with a PLL exciter. the amount of isolation remains the same. It's like a 8 ounce glass, it doesn't matter what liquid you put into it, it still holds 8 ounces. 73 AC0Y
--- In [email protected], "kerry" <[EMAIL PROTECTED]> wrote: > If you are not using a pll exciter, it's hard to get the isolation.......... > Kerry > ----- Original Message ----- > From: "Kevin Custer" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Monday, May 31, 2004 12:07 PM > Subject: Re: [Repeater-Builder] Wacom WP-641, correction on its specs... > > > > Neal Newman wrote: > > > > >I am Getting only 83 db Isolation usning My 641's.. > > >funny thing. I cannot get it to work with my MastrII repeater. But it > > >works great with the Spectrum.. > > > > > > > The obvious question is, is it tuned properly? The Wacom 641 is very > > simple to get close with nothing more than a handheld and a signal > > generator. > > I prefer to tune the pass under low power, like one watt from the > > handheld. It makes the pass more precise, as tuning it with a spectrum > > analyzer usually won't yield as good a loss. I have always been able to > > hit the 1.5 dB loss mark by using this method. PLEASE spare me the > > "Don't tune the duplexer under power BS" These cavities are rated at 350 > > watts intermittent, and 275 continuous and you won't be able to arc the > > fingerstock with a few watts of power, especially if you get it close to > > resonance with a signal generator first. After getting the pass > > frequency 'correct' you will find that obtaining the stated isolation is > > easy. > > > > One thing that happens is if the cavity is not tuned correctly on the > > pass frequency, the reject amount will suffer. Why? As the spacing > > between pass and reject frequencies decrease, so does the ability for > > the cavity to provide the rejection response. With this cavity, the > > lowest loss and best return loss appear nearly on top of one another, so > > match is at its best when the cavity is properly tuned for lowest > > insertion loss. Here is more on pass and reject response with one > > cavity from a WP-641 duplexer: > > http://www.repeater-builder.com/rbtip/wacombpbrnotes.html > > > > Another thing that happens commonly with a duplexer and a radio set that > > was converted from commercial service to amateur, is the actual terminal > > impedance will not be 50 ohms. A duplexer that has been optimized on a > > piece of 50 ohm test equipment *may* not perform very well in practice. > > There are a few things that can be done to help this problem, like using > > a matching device (Z matcher) on the transmitter. Some prefer to match > > the duplexer to the transmitter by adjusting cabling lengths. Either > > method can substantially improve the operation of the duplexer. Sure, > > it would be nice or best if the radio set presented a perfect 50 ohm > > match, but many we convert do not. > > > > Wacom had written a dissertation on optimizing the duplexer > > interconnection cabling lengths. That information, as well as duplexer > > tuning, is available here: > > http://www.repeater- builder.com/pdf/wp6xxVHFtuninginstructions.pdf > > Look on page 4 under the section "Cable length between transmitter and > > duplexer" > > > > Hope this helps... > > Kevin Custer > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > 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/
