Thanks Jeff yes I felt I would need more Q than the stub could provide. I need to get the measurements but the links should have plenty of margin so I felt I could suffer some loss. But if some one has one laying around I would entertain trying it. Could you a power divider as well.
Randy --- In Repeater-Builder@yahoogroups.com, "Jeff DePolo" <[EMAIL PROTECTED]> wrote: > > > A quarter-wave stub of coax won't have enough Q to attenuate the 444.6 > signal without also degrading the 446.x signals as well. A high-Q > pass/reject cavity is the way to go. The bandpass characteristics of a > typical pass/reject cavity should allow both 446.7125 and 446.600 to pass > with near-equal attenuation as they are close in frequency, while still > being able to knock down the 444.6 signal about 40 dB or more depending on > loop settings. > > Before going out and spending money, measure how strong the 444.6 sig is at > your 446.x receivers. That will tell you how much rejection you really > need. If your desired signals are strong, you might only need to knock down > the 444.6 to maybe -20 dBm. If your 444.6 sigs are marginal, it may need to > be down below -30 dBm, but probably not more than -40 dBm for your MVP's. > I'm assming you're not using a preamp, for if you are, it's probably only > exacerbating the problem. > > You could try using filter sections from a duplexer to do this, but most UHF > duplexers are designed for a 5 MHz split, so you may not be able to get the > notch close enough to the pass (about 2 MHz) without incurring high > insertion loss at the pass frequencies. But your paths have enough margin, > maybe you can get away with it. > > --- Jeff WN3A > > > > -----Original Message----- > > From: Repeater-Builder@yahoogroups.com > > [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kraly > > Sent: Thursday, March 06, 2008 9:04 AM > > To: Repeater-Builder@yahoogroups.com > > Subject: Re: [Repeater-Builder] 440 de-sense > > > > how about trying a 1/4 wave stub tuned to his freq on your > > rcv line? That is IF it is coming in there. or is it coming > > in thru the wiring? > > Chuck K0XM > > > > > > On Thu, Mar 6, 2008 at 7:57 AM, wb8art <[EMAIL PROTECTED] > > <mailto:[EMAIL PROTECTED]> > wrote: > > > > > > Hi, I have a slight problem with a 444.6 output > > repeater and looking > > for the best and low cost approach to fix. We have > > just moved to the > > site and the owner has the 440 repeater. The ants are > > all at the same > > height and hence we only have a small amount of horiz > > separation. We > > can't change this as on cell tower as part of the > > owners deal for the > > site. So what it is, is it. We link the the site on > > 446.7125 and > > 446.60, and his repeater at 10 watts, is DE-sensing our > > receivers > > which are GE MVP's. Guess looking to the experts on best viable > > solution. I have been able to try anything yet but > > have considered a > > mobile duplexer as an option. > > > > Thanks Randy >
