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Old 04-08-2014, 11:02 AM
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Question Maratrac

I have a question and hopefully someone will have the answer I am seeking.

I have been using a Maratrac for over a year without problem as a transmitter for a repeater.

Are these susceptible to having issues such as a buzzing or carrier if the supply voltage drops below nominal?
Reason is, the repeater is bringing itself up with a carrier that contains audio such as a buzz or wind type noise, then fades like a signal dropped out on the input, then the courtesy tone is heard. I have been unable to catch it doing this while at the shack. Supply voltage drops might be happening but not while I am there. Also, the power supply is a Motorola MSR 2000 and should be more than adequate for this radio. I suspect a drop in voltage as the controller(cat 1000) is keying the radio.

Thanks,
WD8DK
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Old 04-09-2014, 12:02 AM
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I would not think that an MSR supply would have voltage "sag" unless there is some other problem with it.
Take a voltmeter and key the radio and see how far it drops at the PA and at the controller.
Maybe bad connections somewhere.
If you have been using the Maratrac at high power for a long time, there is a chance that the PA transistors would get pretty hot and possibly partially melt the solder.
Look at the PA transistors and see if the solder looks nice and shiny and "fluid" or if it looks crystalline. Like sparkles.
If it is crystalline, then you could be transmitting spurious signals that would make funny sounds on the repeater input.
Resoldering should fix it.
Try connecting the transmitter into a dummy load to see if the noise goes away.
Could be something external mixing, but look at that PA first.
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Old 04-09-2014, 5:56 AM
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Ok, that was on my list, too. Thanks. However, it randomly brings itself up at times. That is the hard part being there when it does. I will mention this, it made it through some nasty cold weather in the shed this past winter so a cold joint is very possible. Thanks for helping.

Last edited by wd8dk; 04-09-2014 at 6:01 AM..
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Old 04-10-2014, 12:05 PM
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Yes they will. Seen it a bunch in a mobile if the orange and green wires in the mobile cable was hooked in the fuse box and got a little low.
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Old 04-10-2014, 12:27 PM
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Well, caught the bugger making the noisy carrier while at the repeater shed. Wiggled the receiver card and wiring to controller. Nothing.
Slapped the Maratrac for transmitting, BOOM, it cleared up, so replaced with another programmed unit. No noise, no nothing so far. Thanks again Fellas. 73
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Old 04-11-2014, 12:53 AM
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Quote:
Originally Posted by wd8dk View Post
Reason is, the repeater is bringing itself up with a carrier that contains audio such as a buzz or wind type noise, then fades like a signal dropped out on the input, then the courtesy tone is heard.
So the repeater hangs up with a weird noise, then drops with the with a courtesy tone. I'm gonna call a spade a spade and say this sounds like IMD to me. Fault with the duplexer, coax, antenna. Something along those lines. Sure there are reasons to have a noisy transmit from a maratrac and smacking it would cure it. What bugs me is the hang on time before it drops and the courtesy tone beeps. Yea it could be excessive transmitter noise affecting the receiver, but usually I find that symptom originates beyond that. You've swapped out the transmit unit and it's playing OK now. Good luck and see how time reveals the problem...
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Old 04-11-2014, 3:32 AM
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Quote:
Originally Posted by ramal121 View Post
So the repeater hangs up with a weird noise, then drops with the with a courtesy tone. I'm gonna call a spade a spade and say this sounds like IMD to me. Fault with the duplexer, coax, antenna. Something along those lines. Sure there are reasons to have a noisy transmit from a maratrac and smacking it would cure it. What bugs me is the hang on time before it drops and the courtesy tone beeps. Yea it could be excessive transmitter noise affecting the receiver, but usually I find that symptom originates beyond that. You've swapped out the transmit unit and it's playing OK now. Good luck and see how time reveals the problem...
The receiver is the actual MSR card with crystal. The Maratrac replaced the exciter and PA due to issues with the back plane socket and PA. So that is how it is set up. You may be right as the changing stopped the issue.
Thanks.
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Old 04-27-2014, 9:29 AM
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Wow that's not FCC narrowband compliant. You should think about changing that Maratrac for a compliant radio for reasons obvious of course.
If your hung up on Maratrac I have a pile of them that are about to meet the crusher at the scrap yard. Let me know if I should keep one aside
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Old 04-27-2014, 10:15 AM
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If it's an amateur repeater, there's no need to narrowband it.
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