Hi Mike, Since the pager is multi-channel, we were thinking of the DCI window filter on the pager. Then adding what ever else is needed on our ham receiver.
On inverting either of the antennas, no chance. The paging antenna is an 8 bay that is about 40 feet in length. We'd have to drop 60 feet to get any vertical separation. Dwayne Kincaid WD8OYG --- In Repeater-Builder@yahoogroups.com, Mike Morris <wa6...@...> wrote: > > The widow filter on the paging transmitter or on your repeater? > > DCI will do custom designs for special situations, and yours > certainly qualifies. > > If the DCI is going on yours, make sure and plan ahead - I was > told about a guy who had to add a DCI box to his system to > keep out a new-to-the-site NOAA transmitter and since he wasn't > paying for it he made sure to include in the specs that it would > not affect anything in 144-148 Mhz rather than just his 2m > pair - just in case he had to change frequencies down the > road or he wanted to sell it. > > Another thought - any chance of inverting one of the antennas? > (i.e. let the paging antenna sit above the crossmember and you > suspend below the crossmember). > Just getting your pattern a few feet below his might make enough > dBs of difference and avoid the insertion loss of the DCI, and a few > feet won't cost you THAT much coverage. > > One local system had a piece of pipe center-mounted to the tower, > with the 440 antenna mounted to the top of it and going up, and the > 2m antenna mounted to the bottom of it and going down. A high > power 460 repeater was added and ended up on the adjacent tower > position. The cure was to exchange the antenna positions - the 2m > took the broadside and the 440 was below the pattern. Problem > solved. > > Mike WA6ILQ > > At 01:33 PM 08/08/10, you wrote: > >Hi Mike, > > > >Excellent information. It's a new pager and it's a two channel > >system, no cans. We're the ham guys and have been there for about 5 > >years, but only as guests. Yes, there is a non-interference clause, > >but we do not want to go that route. > > > >We're all on good speaking terms (tower owner, ham group and pager > >guy) and since we're the guests, we'd like to help solve the problem > >(rather than just point fingers). The pager transmitter is running > >100 watts to a 9 db antenna that points away from our 6db omni. > > > >I agree that we're probably getting only 10 to 15 db of isolation at > >15 feet (yes, already checked the RB site). Moving either of the > >antennas is not really an option. It's only 170 feet and we both > >want the top (in flat-land Maryland). > > > >The DCI box on the pager looks like it will give about 40 db to our > >rx freq and we'll add a notch (40db) and a pass (30 db) to get the > >total to just over 100. > > > >We added the pass and notch last week and it work on all but the > >weak signals. So we're thinking a little window filter will take care of it. > > > >Dwayne Kincaid > > > >WD8OYG > > > >--- In Repeater-Builder@yahoogroups.com, Mike Morris <wa6ilq@> wrote: > > > > > > At 11:38 AM 08/07/10, you wrote: > > > >Hi, I've got a new pager issue that has come up on a tower where we > > > >have a VHF repeater. It's about 400 watts erp and 15 feet horizontal > > > >distance and 4.3 and 4.7 MHz away (it switches). > > > > > > > >I'm thinking of using one bp/br can that will have the notch wide > > > >enough to cover both channels and one pass can on our RX freq. I can > > > >also add more pass cans or something like the DCI window filter. > > > > > > > >The real question is where to these can go and in what order. We > > > >have a standard Q-202 duplexer that worked fine before the pager was > > > >put in. I'm thinking that the pager cans will go on the RX side of > > > >the duplexer, but does it matter if the pass goes on the duplexer > > > >side or the RX side of the bp/br can? I'm kinda thinking that it > > > >doesn't matter, but want to do it right in case it does. > > > > > > > >Dwayne Kincaid > > > >WD8OYG > > > > > > Is this a situation where the paging transmitter is a > > > new install, or a situation where the paging company > > > consolidated two transmitters, each a single frequency, > > > into one that switches, or a new ham system install? > > > > > > If it's a new paging transmitter install, then 400 watts erp > > > and 15 feet horizontal distance, is too damn close. Your > > > antenna is broadside to its antenna and you have a nice > > > coupling situation. > > > It reminds me of a repeater that was located at an FM broadcast > > > site, and we saw 35 (or so) watts of 90.7 MHz coming DOWN > > > the ham feedline. The ham duplexer was nice and warm... > > > > > > If it's a consolidation I'll bet that the paging transmitter has no > > > pass cavity, or any other filtering - if it ever had any it was probably > > > removed in the consolidation. > > > Digital paging transmitters use square wave modulation and are > > > DIRTY when they have no filtering and local stories have it that > > > the FCC has cited several consolidated transmitter systems. > > > > > > Paging companies are notorious for running overpower. One local > > > situation had a license for 90w and they were found to be running > > > 350w. They were cited, changed transmitters, and a year and a > > > half later the interference returned. A no-notice visit from the FCC > > > found then running 500w. > > > > > > Don;t order that DCI box yet - the first thing I'd do is reduce the > > > antenna-to-antenna coupling. If the master site agreement has a > > > no-interference clause perhaps you can get them to relocate an > > > antenna, or go back to the two transmitters with filtering installed. > > > Look at <http://www.repeater-builder.com/antenna/separation.html> > > > Depending on your antenna gain I'd be very surprised if you are > > > getting even 15db of isolation. > > > Once you have reduced the coupling as best as you can, I'd > > > then re-evaluate the situation by jacking a spectrum analyzer > > > into your antenna and getting some hard numbers, a screen shot > > > (even a digital photo of the CRT) posted here, etc. Then we can > > > help a lot more. > > > > > > Mike WA6ILQ > > > > > > > > > > > > >------------------------------------ > > > > > > > >Yahoo! Groups Links > > > > > > >
