Well, you don't really need my input, you certainly have gotten plenty of quality responses tonight...
Don't let the flurry of ideas overwhelm you. Take it one step at a time. You still might be too low on the power output. I had a transmitter that didnt like to be turned down less than 2/3 rated power, at 1/2 power it would create problems on the reciever, its spurs would mix with some local 2-way stuff and come thru on the receiver from time to time, had me convinced it was local interference and I needed filtering. Turning up the power solved the problem. KISS method is always a worth a try. There are way more qualified guys on the list here to help you, but here is what I would do (without having a spectrum analyzer to look at your output): 1. Terminate the TX into a dummy load. Turn the power up to 80W. Key the transmitter for a good long time and get it warmed up. Keep your wattmeter in line and watch it, make sure it stays stable at 80W. If you notice it acting up then you have a problem in the radio. If not- go to step two. 2. Once the transmitter is nice and warmed up have someone with a weaker signal start giving you a signal on the input. Leave the transmitter hooked up to the dummy load for this test and the reciever hooked up to the antenna system. First, disable the transmitter and have them continue transmissions while you monitor the input. It may take several tests like this if it is outside interference, since it's likely not consistent. Try and notate any particular times of day the noise happens to get a better clue into this. If you do hear the noise, then you know its interference or something in the antenna system. If not, then move on to step three. 3. With your friend still sending a signal on the input enable the transmitter into the dummy load. If the noise appears then something in the radio is amiss, like the PA is going spurious or there's a bad jumper or connector somewhere . If not- move onto step four. 4. Reconnect everything back to normal. Leave the power level at 80W. If the noise re-appears then you still need to look into the antenna system. The G7 could have a problem, or something in the feedline. If all is well then it was likely the power level of the PA was still too low. Problem solved! Hopefully one of these steps without the proper test gear will get you pointed in the right direction. Let us know your findings! Tom W9SRV --- On Mon, 10/5/09, W3ML <[email protected]> wrote: From: W3ML <[email protected]> Subject: [Repeater-Builder] Re: Radio for repeater use Response to Tom's comments To: [email protected] Date: Monday, October 5, 2009, 7:33 PM Hi Tom, I did crank up the power to 55 watts out of radio and that gives me 45 out of the duplexer. Decided on this wattage until I can figure the problem better. It is working better than before, but still having trouble. So from what you said about power coming out duplexer, the duplexer must still be okay. However, during the day today there were 3 hams talking and they said (later) that all of them were loud and clear. But, when I got home and tried to call one of them, he was covered in noise. Later one of the others called in and he would be clear, then the repeater would cut out and his signal would be gone, then it would come back with noise on his signal and then clear again. Then the other one came in with a lot of noise, then he would come in with a little noise and then no noise at all and then back again through this cycle. This cycle of noise and then no noise is driving me crazy. The set up is this: GE Mastr II VHF mobile running into a 6 cavity duplexer set to our freqs with a service monitor prior to bringing it here. There is a bandpass filter on the receive side after the duplexer and before the radio. We have used 1/2 inch hardline going up to the used G7-144. Then only thing I can think of is the radio is bad, the antenna is no good and the coax is shot. Now, the radio was given to us by a group that had used it, but decided to replace it with a Kenwood. I am thinking that they had the same problem and that is why they gave it away. Any advice would be greatly appreciated. 73 John, W3ML - In [email protected], W9SRV <tgundo2...@...> wrote: > > Ok- > > 1. Where are you checking the swr at in the chain? Make sure you bypass the > duplexers to check the antenna, the cans can throw off the reading on some > meters like you describe using. If you are less than 1.5:1 I would not worry > too much more about it, any reflected power will get eaten up back in the > cans. If you are really concerned about protecting the TX put a circulator > in-line with it. > > 2. Make sure all the interconnecting cables are good shielded and not foil/ > braid type. RG-213 and RG-400 are good choices, though there are a few more. > > 3. Terminate into a good dummy load. Set you output power to 80-90W. Then run > thru the duplexer and check the power coming out of the cans. You should see > something like 60-70w, depending on the spec of the duplexer. If your seeing > much less than you may have a duplexer tuning issue. > > Figure out the real problem, let the radio run at a real spec power output, > than absorb the title of "far lord" as every one thanks you for giving the > repeater twice as many s-units. (then be prepared for the next round of > complaints that become your problem) > > Tom > W9SRV > > Sent from my iPhone > > On Oct 4, 2009, at 5:46 PM, "W3ML" <w...@...> wrote: > > No, except when it was at the 2o watts the swr was almost 1 and someone said > that was the problem causing the de-sense. So we were afraid to run it > higher. > > Like you said guess it was only a problem from running too little of power. > > > Thanks and 73 > John > > > --- In [email protected], W9SRV <tgundo2003@> wrote: > > You answered your own question : > > "So it appears that this radio, which is a GE Mastr II mobile, doesn't like > to run at the lower wattage of 10 to 20 watts out." > > 110w radio will not be stable at 10-20w. If you look at your output on a > spectrum you probably have spurs all over the place. Any reason you cannot > run it at least 1/2-2/3 power? > > Tom > W9SRV > > Sent from my iPhone > > On Oct 4, 2009, at 4:46 PM, "W3ML" <w3ml@> wrote: > > So it appears that this radio, which is a GE Mastr II mobile, doesn't like to > run at the lower wattage of 10 to 20 watts out. > > > > > > ------------------------------------ > > > > Yahoo! Groups Links > ------------------------------------ Yahoo! Groups Links
