Scott & Brian, Putting an attenuator in the rx line only attenuates the desired and desensing receive signal. Still the desired signal to desensing signal ratio will still be the same one should still see the desense with the attenuator, just require more desired signal to overcome it. Except for isolation cannot see whey the attenuator would help. If desense is caused by another RF path, such as bad cables, getting around the duplexer one would see the desense being worse due to rx signal reduced, but desense not reduced.
If you replaced any of the cables including between duplexer and repeater, make damn sure the cable is NOT 9913. This will cause noise resulting in desense. The solution is to find out why you have desense and fix it. 73, ron, n9ee/r Ron Wright [EMAIL PROTECTED] Ron is the owner of Micro Computer Concepts, a manufacture of repeaters and repeater controllers since 1988. You may see our products at http://home.earthlink.net/~mccrpt or call at 727-376-6575. Contact me at 8849 Gum Tree Ave, New Port Richey, FL 34653 USA Owner of the 146.64 repeater, the highest repeater, 1175 ft HAAT, in the Tampa Bay area, Florida. The repeater also has ECHOLINK, node 79540. Pasco County Skywarn Coordinator Skywarn meets on 146.64 each Wednesday at 8 PM. Skywarn nets are activated on 146.64 when the National Weather Service broadcast a weather alert. see our web page at http://groups.yahoo.com/group/pascoskywarn/ All are welcome. > [Original Message] > From: Scott <[EMAIL PROTECTED]> > To: <[email protected]> > Date: 7/11/2005 10:03:32 AM > Subject: Re: [Repeater-Builder] VXR-7000 > > Put a 50 ohm step attenuator in series with the receiver feedline---i.e. > between the duplexer and the receiver antenna input. Add attenuation until > all desense problems just go away. This is the additional attenuation you > need from your duplexer due to the improved sensitivity of your new receiver > and increased transmitter power if there is any. All things being "good" and > assuming that you haven't added appreciable transmitter power, the repeater > should work about as it did before with the attenuator in place. Improve the > duplexer to enjoy the improved receiver performance ----that is a repeater > that "hears" better than before. > > Scott, N6NXI > > > > > > > > ----- Original Message ----- > From: "Brian" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Monday, July 11, 2005 3:39 AM > Subject: Re: [Repeater-Builder] VXR-7000 > > > > As far as what has changed....the new piece of equipment(repeater) is > > by the specs more then twice as sensitive but on the bench it tested > > more like 3 times as sensitive as the old repeater. We are going up > > today to try some more testing and I will get back to this thread > > with the results. > > > > > > >Brian wrote: > > >> Our local club has been running a 10 Yausu 2410 2 meter > > >> repeater for many years. It is run through a Wacom wp-641 4 can > > >> duplexer. Great results from this unit and it hears excellent....We > > >> recently aquired a new vertex vxr-7000 do to some really nice friends > > >> locally. In hooking up the new machine we have terrible desense on > > >> lower signals that would still be full quieting into our old machine. > > > > > >First off, just in case of a common mistake: If you replaced the cables > > >going to the duplexer and didn't replace them with good quality > > >double-shielded cable... stop and go do that right now. > > > > > >How much isolation is the Wacom providing, since you just had it tuned. > > > Did the shop give you a report for what they really got out of it? > > > > > >Does the repeater desense into a dummy load, or only if the antenna is > > >attached? > > > > > >Do you have a directional coupler and/or Iso-T that you can inject a > > >weak signal into the repeater with in both scenarios so you can see if > > >the antenna or feedline are part of the problem? > > > > > >Back to a previous thread - do you have an Isolator on it? Are there > > >other high power transmitters near you that could be getting into your > > >transmitter? What's the site like? > > > > > >Do you have any way to see if the transmitter is clean at your selected > > >power output level both into the antenna system and into a dummy load? > > > > > >> We had a local shop retune the duplexer and still no luck. We have > > >> tried it both with and without the contorller hooked up and no luck. > > >> It hears and transmits great in base mode but falls apart in repeat. > > > > > >I wouldn't have suspected the tuned cavity first - unless you dropped it > > >and dented it or something. Cavity size and frequency are physical > > >properties that don't really change much. > > > > > >Something else is more likely to have changed. > > > > > >Nate WY0X > > > > > > > > > > > > > > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > > > > > > -- > > [EMAIL PROTECTED] > > Amateur Radio Callsign: KC0DWX > > WARN (Weather Amateur Radio Network) member > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> 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/
