Ralph you bring up a good point of thought. The ham that built our repeater placed the Decibel Products 4002 Bandpass behind the Wacom 6 can duplexer and then followed by the ARR Gasfed P144VDG to the radio.
Now where he built it was his tower site (an old AT&T brick building) full of transmitters. Now that we have it, it is located here at my house in my ham shack. So, the only transmitters are my 2 meter and HF when I am on HF. The HF doesn't bother it at all and I run low power on 2 meter when I am on that. So, with your thought, I could probably do away with the bandpass all together run the preamp right out of the cans to the radio (which is a GE Mastr II mobile). Right (after fixing a lot of problems which most of you should remember) it is working good. Of course, you always to improve something even if it works like handheld access, so when I came across that article it made me want to ask where should the preamp go. I looked on the ARR site and they have no info on placement that I could find at all. Now maybe, if we had bought a new one, it might have came with a paper. Thanks for the advice. 73 John --- In Repeater-Builder@yahoogroups.com, Ralph Mowery <ku...@...> wrote: > > > > --- On Wed, 11/25/09, W3ML <w...@...> wrote: > > > From: W3ML <w...@...> > > Subject: [Repeater-Builder] pre-amp placement > > To: Repeater-Builder@yahoogroups.com > > Date: Wednesday, November 25, 2009, 10:46 PM > > Hi, > > > > I have now read two different things about where to put the > > pre-amp. > > > > One says before the Bandpass and one after. > > > > What I have now is the 6 can duplexer is hooked to the > > bandpass and then on the other side the pre-amp is connected > > and then a cable goes from preamp to radio. > > > > The other article I read this past week says the preamp > > should go between the cans and the bandpass. > > > > Which is right? Or does it matter? > > > > 73 > > John > > > > > > As always it is one of the "it depends" answer. You want the preamp as close > to the antenna as you can get it. This sets the noise figure or in simple > terms the minimal signal you can detect. Idealy it should be right at the > antenna. This is not possiable with a repeater and single antenna so you > want it right after the duplexer going to the receiver. Sometimes if you are > in an area with lots of transmitters that are overloading the receiver or > causing other problems (which is probably your case or you would not need the > banpass cavity) then the preamp goes between the banpass cavity and the > receiver. > > Most preamps do not have very much selectivity and many duplexers don't > either to signals outside the tuned frequencies. This lets the preamp > amplify many undesired signals and can cause all kinds of problems. > If your repeater is located very far away from other transmitters this is not > usaully a problem. If there are several transmitters near by then you may > have a problem without a band pass filter. >
