Watch your signal strength meter on your radio. The input signal may not be weak enough to hear a "noisey-quiet-noisey" Actually while tuning for a notch you need to be listening to the freq you are trying to notch and it will be a "quiet-noisey-quiet" as you move the notch rod on the side. Tune for most noise (weakest signal).
First consult the tuning instructions on where to set the notch adjustment rods for starting point. You should set all the (4) pass adjustments first You have to tune the pass first, that is the threaded rod in the center of the can. You can do this by transmitting (you can use an HT or mobile on low power for this) on the freq you want to pass and adjusting (not while transmitting) for least reflected power into a dummy load or antenna. Do this one can at a time then put them all back together and terminate the open port into a dummy load. check the reflected power again it should be very close to where it was with only one can if not you can tweek the first pass adjustment. Do not move the pass adjustments again. Now for the notch you will have to be receiving a weak signal on the freq you want to reject (this is where a variable attenuator helps) and adjust the rods on the side of the cans you just set for the freq you wanted to pass. Adjust the rods for weakest signal on your signal strength meter. Adjust one then the other until you get the weakest possible signal. You will have to move the rods "as far as it takes" there is no set answer as to how far to move the rods. Then repeat the above notch adjustment procedure for the other set of cans. hope this helps. I have tuned several with nothng more than a signal generator and a ht with a signal strength meter. After I got the right equipment I found little to no improvement in performance when retuned with the service monitor. tom > [Original Message] > From: hbbcara <hbbc...@yahoo.com> > To: <Repeater-Builder@yahoogroups.com> > Date: 7/18/2009 10:44:30 PM > Subject: [Repeater-Builder] wp-639 -- How far should I expect to move the invar rods? > > > Hi all, > > In tuning the reject for a wp-639, how far should I expect to move the > invar rods to find the notch? > > In tuning mine (the poor man's way - system on the air receiving a weak > station) I didn't find a definite place I"d call a null. There was more > noise on the signal with the rod pushed most of the way in and less > noise with the rod most of the way out, but it was a gradual change. I > expected to find it noisy with the rod mostly in, noisy with the rod > mostly out and at some point in between a quieter spot. > > SO my question is, should I hear a definite > pattern as I move the rods and if so, over how much motion of the rods > is it likely to fall? An inch? Half-inch? Three inches? Or would that > pattern only be noticeable with "the right equipment." > > (Some background - the duplexer is from an uncertain origin, but it has > a factory sticker saying 146.97 - 146.37 with the ports marked "high > input" and "low input." I'm using it on 146.88/28 so it shouldn't be an > "upside-down" issue.) > > Thanks for any info! > > rj > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > >
