[Allstar Digital] Fwd: [MTUSA] Fwd: [pnw-dmr] Re: Tytera MD-380 Digital Timing Issue

Fri Dec 18 10:47:14 EST 2015

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 at trbo.org [mototrbousa]" <mototrbousa at yahoogroups.com
>
Date: Dec 17, 2015 8:29 PM
Subject: [MTUSA] Fwd: [pnw-dmr] Re: Tytera MD-380 Digital Timing Issue
To: "mototrbousa" <mototrbousa at 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 at trbo.org
<no7rf at trbo.org?subject=Reply+to+my+.sig>, www.trbo.org

== == == == == == Forwarded message == == == == == ==
>From : <pnw-dmr at 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 at trbo.org
<no7rf at trbo.org?subject=Reply%20to%20my%20.sig>, www.trbo.org
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