Batboard

Not sure if this is the right forum.
A client has a number of new MTR3000. They have a distorted audio problem, which I am trying to debug from a great distance.I don't have the MTR3000 yet, but I have the CPS and Tuner. My question is about the TX Modulation Limit. First you set Wireline Transmit Level, then Wireline Squelch Level, then TX Modulation Limit. It appears my client is setting TX modulation limit to 75%. He then overdrives the wireline input trying to reach 5kHz deviation (WB). I think he should set TX Modulation Limit to 92%. Then he should get at least 4.6kHz deviation. I would appreciate some feedback as this is the first MTR3000 I have encountered. Thanks

You're kidding? That's what it was? They can set it for 100% if they want. 92% is okay too. Keeps any possible peaks from exceeding max dev. But, 75% is a wee bit low.

And you shouldn't have to set wireline squelch except if you have a noisy line.

I am still not sure what is going on, because he won't respond to my emails and won't send me a codeplug or an MTR3K.. But the handwritten data he sent me stated a Mod limit of 75%.......he also stated his Wireline Transmit Level pot was set to 11. Is that reasonable since his input level is 0dBm?
(Moto says up to +10dBm is OK)

Thanks

Turning a pot to 11 is a joke. "My guitar amp is better than yours cuz I can turn it up to 11. Yours only goes to 10."

If you align for a given input, you can shove just about any level into it. Ask him if he has performed the tx wireline alignment procedure. If he aligns to 0db for full deviation, and he inputs +10db, he can expect distorted tx audio. If he aligns for +10db for full deviation, it will give full deviation (with some compression by the IDC) with +10db input that sounds fine. He has to perform the alignment procedure. And he should turn the input down to something reasonable like -10db for full deviation.

And he should set the mod limit to 92% or higher. This isn't the old days where you set the voice limit at 75% to leave room for the PL. The radio handles the ratios automagically. He just tells it where to apply the limit to the overall deviation, and he wants that number high. He can adjust that value down if he has adjacent channel issues to help preserve the guard band for his neighbors. But, if his station is out there in lonely country without a radio neighbor for miles, he can go for max deviation and never cause a problem.