I've heard the anecdotal evidence from West Palm Beach. I know the guys involved but I have not talked to them directly about the issue. The empirical data Mike is reprinting does look compelling. Jerry from CSI says he has also seen it on real test equipment. I have not seen it happen here, and I wish I had the equipment. I mostly listen just to my MD-380 at the work QTH, so I'm not too worried. Keep you eye on the front panel of your repeater while you setting up. 

Steve

On 12/18/2015 10:47 AM, Robert Newberry wrote:

Has anyone else seen this? I am forwarding it from another list. I'm not doing this to trash the md-380, it's technical and I thought the list might want to see it.

N1XBM
Apparare Scientor
Paratus Communicare
Allstar Node # 27086, 41540, 41812, 42086, 42658
   

---------- Forwarded message ----------
From: "Mike N07RF no7rf@trbo.org [mototrbousa]" <mototrbousa@yahoogroups.com>
Date: Dec 17, 2015 8:29 PM
Subject: [MTUSA] Fwd: [pnw-dmr] Re: Tytera MD-380 Digital Timing Issue
To: "mototrbousa" <mototrbousa@yahoogroups.com>
Cc:

 
I am forwarding this information as it is near first person and involves Aeroflex actually taking a look at the problems that we have been hearing with hams using the MD-380.  While the 380 users may not appreciate the issues, those who do hear them, should.

I've neutered the attribution only as I don't have permission to forward the post.

At this point, I'd caution folks to consider looking at other DMR radios, if not for their first DMR radio, then for their move up with subsequent purchases.  If a MotoTRBO radio is not on your RADAR, then the CS-750 has a great value to cost ratio and is DCI's recommended alternative if cost thrumps compatibility.

-- Mike, NO7RF, Mazama Washington, no7rf@trbo.org, www.trbo.org


== == == == == == Forwarded message == == == == == ==
From : <pnw-dmr@yahoogroups.com>
Date : Thu, 17 Dec 2015 17:14:59 -0800
Subject : [pnw-dmr] Re: Tytera MD-380 Digital Timing Issue
== == == == == == Forwarded message == == == == == ==
 

Here is another Tytera MD-380 observation.


(In) December, I attended a digital radio service presentation by the well-known service monitor company Cobham/Aeroflex.  I brought my 450 MHz MD-380 along.

After the presentation, I asked Mike Fortna of Aeroflex to take a look at the infamous MD-380.  He said Tytera had contacted them about developing an Autotest routine for Tytera products, so Mike was interested in seeing the Tytera MD-380's alignment.

Testing was done on 441 MHz Simplex and again on TS1 on the Gunnysack pair with the Cobham/Aeroflex 8800S Digital Radio Test Set.  The 4FSK modulation was perfect.  Mike had just been explaining that most problems with alignment are revealed on the 4FSK display, but the Tytera was perfect.  I asked him to look at the energy in each timeslot.  I think this display is called the power profile.  The graphic showed timeslot 1 and 2 simultaneously.

What was observed was a non-standard rise time when keying the transmitter.  The power in timeslot 1 came up about half of maximum, hung there for a few uS, then went to full power.  It was not a nice rounded envelope.  It was a stair step.  No overshoot was observed.  Other than the "stutter" in reaching full output, the waveform was mostly normal.  The abnormal condition was likely caused by the "stutter" in rise time.  This abnormal condition is RF energy "spilling over" into timeslot 2 in this case.  It seemed to appear in timeslot 2 for the same duration as the stutter in the timeslot 1 rise time.

Mike Fortna of Aeroflex found it interesting enough to take a screen shot.  He stated it was a better example of a DMR power profile alignment problem than what he was currently using.  

The same waveform anomaly occurred on Simplex and Duplex.  Rapid keying, de-keying and keying again made no difference in the waveform.  I have read that transmitting on both timeslots simultaneously was a "feature."  This doesn't seem to be true.

I didn't have time to test on timeslot 2.  Testing was rushed because everyone knew that Seattle traffic was building!

Further, more comprehensive testing is required with a greater pool of radios. It would be interesting to test some high-band models as well.  Does anyone have an IFR3920 or 8800S with the DMR option?

This only meant to be a verbal description of the graphical representation of an anomaly in my particular MD-380's timeslot power profi le.  Your mileage may vary, as they say.
-- Mike, NO7RF, Mazama Washington, no7rf@trbo.org, www.trbo.org
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Posted by: Mike N07RF <no7rf@trbo.org>
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