Maybe I missed something, as I am distracted this morning with the kids and Christmas. Does the receiver interference still happen when the transmitter is NOT on?
Try taking the transmitter to about %30-40 power and then see if you still have the problem. Also, get the biggest UPS you have or get a big 12V DC to 110 AC inverter running on a car battery. Shut down all power to your house an see if you still have the receiver interference problem. ------ Original Message ------ Received: Thu, 25 Dec 2008 07:35:00 AM PST From: Joe <[email protected]> To: [email protected] Subject: Re: [Repeater-Builder] Six Meter Repeater Noise Issues > First of all, 6 meters can be a very noisy band. But the noise you > describe sounds like it is something different. What kind of antenna > are you using? > > Let me take a wild guess. The 7.2kv line is inducing noise on your > antenna feedline. It goes away when you take the feedline off the > antenna and put the dummy load on because you broke the ground loop that > you had when the feedline was grounded at both ends. Try grounding the > feedline to the antenna mount while the dummy load load is connected. > This will provide the ground loop that I am describing. If the noise is > present, it's probably being caused by the 7.2k power line inducing > noise on the feedline when both ends are grounded. > > If this proves to be the problem you may have to devise a way to choke > off the noise coming in on the feedline. I think the MASTRII had an > option to isolate the antenna from ground so that positive or negative > ground could be used. I don't remember if the MASTR Pro had the same > option, but it may be a potential fix. Let us know what you find. > > 73, Joe, K1ike > > Tom Elmore wrote: > > > > Several months ago I put a six meter machine on the air in my > > area. It is a GE Master Pro tuned for 52.810 out and 51.110 in. > > One of the things still nagging me is some sort of desense or RF > > phase noise, let me explain. After tuning up the duplexers into a > > dummy load and running some tests I experienced no desense all the > > way down to about .15uV. I moved the dummy load to the end of > > the transmission line just to be sure and again the same results. > > When I put the antenna in line and run the same tests this is what > > occurs. When I key the transmitter and set the output of the > > signal generator from a starting point of say 100 uV I hear what > > sounds like phase noise or just plain static just slightly in the > > background. As I bring the signal generator output down the > > background noise gets louder but it never wipes out or overloads > > the receiver altogether as I can still hear the generator and the > > background noise and this is down to the same squelch threshold I > > get when on the dummy load. I am hesitant to call this desense as > > say when one of the duplexer cavities isn't tuned correctly. Then > > it is obvious because the transmitter totally wipes out the signal > > I am feeding it from the signal generator. I thought perhaps the > > preamp was the culprit so I took it out of line but sill > > experience the same issue. I am thinking that possibly the > > repeater output from the antenna is getting back into the repeater > > cabinet? I took a handheld scanner and set it on the same > > frequency as the receiver and connected directly to the rx port on > > the duplexer and can hear the noise there as well. I do hear a > > slight buzzing in the audio of the receiver almost like 60hz > > whenever I key the transmitter with the squelch wide open and no > > input signal present using the antenna. I don't hear it when using > > the dummy load though. I would like to think that the duplexer is > > tuned correctly or fairly close as there isn't any desense when > > terminated into a load. The last thing there is a single phase > > 7200 volt primary line servicing our neighborhood probably less > > than 100 feet from our house that I wonder is the culprit. I don't > > hear any arcing or power line noise with just the receiver squelch > > open but maybe when I transmit there is some mixing going on? > > > > > > > > > > > > > > Thank You > > Tom Elmore KA1NVZ > > Anchorage, Alaska > > > >
