We have an MTR2000 that's suddenly developed a wireline level issue. The station was initially set up with a -10dB reference for 100% deviation. Tx deviation at that point was 1.87k with a -10dB 1kHz signal. It was decided to realign the wireline card with a -6dB reference level for 100%. After the station reset, Tx deviation would only show 0.9k with a -6dB 1kHz signal applied. An attempt was made to change back to a -10dB reference; after reset that station still only shows 0.9k of deviation with any level that is applied until you hit it with 0dB. At 0dB deviation is where it should be (1.87k @1000Hz).
I think I've seen this once before, but can't remember what (if anything) had to be done to recover from it. Can anybody refresh my memory about this problem?
MTR2000 Tx Wireline Levels
Moderator: Queue Moderator
Re: MTR2000 Tx Wireline Levels
Ha! You're not the first one to be bitten by the "alignment procedure". MTR's are notorious for low deviation. As you saw, the process is automated - you inject -10db, and then hit save. Now it's further down then when you started. The fix is to reduce the input level, save, and check it with a -10 in to see where it lands. Rinse, repeat. Keep doing that until it gets the deviation you want.
Really, the place to start is the transmit alignment especially since you can't get more than 1.87khz dev. First, go into Personality / RF Options, and set Max Dev for 100%. Prog to the radio. Next, go into Service / Station Alignment and do both Tx Dev and Ref Mod. Since there are several freqs to adjust, best to do this straight into the service monitor rather than the duplexer or combiner. Get the ref mod slopes reasonably flat. They are never perfect. On Tx Dev, whatever the value reported by your service monitor is, subtract at least 500hz. You may be back in this screen to subtract some more later. Now, do your TX wireline with a -15db in, but tell it -10db - save - reset - check it on the air.
If it's a repeater, check those levels first. If levels are low, go back into the Tx Dev screen again, and subtract another 500hz on the freqs closest to yours. Keep doing this until you can get a combined voice/PL of 2.5khz deviation. Check it for linearity - ie: 1khz dev in equals 1khz dev out, 2khz in, 2khz out, etc. Once you have that dialed in, then you can set the Tx Wireline using the same reverse logic - go down to go up, and go up to go down. You'll get the hang of it so that eventually you will have a station that gives full deviation with -10db input, or -6db in your case.
Personally, I'd stick with neg ten because it's a good number to remember, and it gives you some headroom for dynamic range when Sgt Bellows gets on the radio as opposed to Officer Mumbles.
Really, the place to start is the transmit alignment especially since you can't get more than 1.87khz dev. First, go into Personality / RF Options, and set Max Dev for 100%. Prog to the radio. Next, go into Service / Station Alignment and do both Tx Dev and Ref Mod. Since there are several freqs to adjust, best to do this straight into the service monitor rather than the duplexer or combiner. Get the ref mod slopes reasonably flat. They are never perfect. On Tx Dev, whatever the value reported by your service monitor is, subtract at least 500hz. You may be back in this screen to subtract some more later. Now, do your TX wireline with a -15db in, but tell it -10db - save - reset - check it on the air.
If it's a repeater, check those levels first. If levels are low, go back into the Tx Dev screen again, and subtract another 500hz on the freqs closest to yours. Keep doing this until you can get a combined voice/PL of 2.5khz deviation. Check it for linearity - ie: 1khz dev in equals 1khz dev out, 2khz in, 2khz out, etc. Once you have that dialed in, then you can set the Tx Wireline using the same reverse logic - go down to go up, and go up to go down. You'll get the hang of it so that eventually you will have a station that gives full deviation with -10db input, or -6db in your case.
Personally, I'd stick with neg ten because it's a good number to remember, and it gives you some headroom for dynamic range when Sgt Bellows gets on the radio as opposed to Officer Mumbles.
Re: MTR2000 Tx Wireline Levels
Thanks, Bill.
Out of the 100 plus MTR2k stations we have installed I knew I'd seen this once before, but couldn't for the life of me remember how to recover. Since we're sending QCII, we were already using -10 from the BIM as a reference, but wanted to knock it down a little because, as you know, Motorola (in their infinite wisdom) sends paging tones highly boosted from the Gold Elite. We were seeing major clipping on the lower tones, and thought maybe we could "split the difference" at the station for cleaner audio.
If you don't mind, any tips on cleaning that up?
Out of the 100 plus MTR2k stations we have installed I knew I'd seen this once before, but couldn't for the life of me remember how to recover. Since we're sending QCII, we were already using -10 from the BIM as a reference, but wanted to knock it down a little because, as you know, Motorola (in their infinite wisdom) sends paging tones highly boosted from the Gold Elite. We were seeing major clipping on the lower tones, and thought maybe we could "split the difference" at the station for cleaner audio.
If you don't mind, any tips on cleaning that up?
Re: MTR2000 Tx Wireline Levels
MTR's have crude equalization settings in the TX wireline screen. Some of the tone clipping is normal. The IDC circuit does that. QCII paging doesn't care whether they get pure tones or not. So, you might not need to worry about it.