Thanks Skipp025! I have an old Lampkin service monitor and I've been tuning the duplexer by using my handheld as a receiver with the Lampkin as the generator. It just doesn't have enough oomph for proper tuning of the reject portion of 2 cans in series.... So I'm working "somewhere" in the notch... not good enough. I'll be looking for use of a proper service monitor, and probably keep using the MSR2000 unit -- it fits my installation better than the Wacom.
On Dec 20, 2007, at 6:09 PM, skipp025 wrote: > > Cort Buffington <[EMAIL PROTECTED]> wrote: > > Repeater Builders, > > I pose to you all a question. I have two UHF duplexers, both 4 > > cavity pass-reject. One is a Wacom (the ubiquitous 3U rackmount > > guy) and the other is from a Motorola MSR2000. > > Both very fine units for what they are. > > > I have really poor equipment, and don't necessarily "trust" > > manufacturer specs. Anybody have an opinion on which one is > > better, or pros and cons to each? > > Nothing bad to say about each one... > > > The rest of the RF equipment are Hamtronics T304 and R305 > > and a Mirage D-1010-RN. The T304 is "throttled" back so > > that the Mirage is making about 55-60W. I'm currently running > > on the MSR2000 duplexer, not tuned as well as it could be. > > Some desense, and some is probably curable with better tuning > > of the duplexer, > > Nat's-a$$ alignment of the duplexer including the notch positions > will make a large difference in the overall system performance. > > > helical preselector on the front end, etc. > > Depends on how the helical pre-selector is constructed. Some designs > have active included active preamplifiers and some are straight > forward filters, which are "only so helpful". > > > But so far, I'm finding the additional receiver sensitivity > > (over say a Mitrek/MSR or Micor) is far out-weighing the desense > > 73 DE N0MJS > > Cort > > Most of the current Hamtronics Receivers are red-hot in the > sensitivity department, pretty fair in the 3rd order intercept > performance and "fair" in the "blocking" performance spec. > > The elephant in the room is the 60 watt output PA and the > relatively unprotected receiver front end. > > A complete/proper duplexer alignment will be the most bang for > your buck. In specific you need to ensure the duplexer band-reject > notch frequencies are properly spaced. > > A non-technical broad statement regarding duplexer notch and > band-pass operation. Relative to the grand scheme of things more > relative performance is often gained with strong/deep notch-out > performance (of the unwanted other frequency) versus band-pass > only (of the desired frequency). > > Folks with modest resources often adjust band-pass, band-reject > duplexers using the max power into a watt meter/load method. > Much system performance is lost when the reject-notch tuning > is discounted or ignored for lack of proper test equipment. > > Unless you know for sure someone has properly aligned the duplexer > notch (band-reject) positions you can and should assume they > are not exactly in the best possible position. > > Once again... the duplexer reject notch adjustment is another > one of the few repeater performance "free lunch" items, which > should not be ignored. Because there are only a few "free lunch" > items on the menu. > > cheers, > s. > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/Repeater-Builder/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> 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/