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This is
preliminary and waffling pending more comments from other TRBO users
MotoTRBO radios can be programmed to
enable AGC action on the mic inputs and is enabled by
default. Some issues have surfaced that have caused us to
re-visit the default use of AGC in the digital mode.
At this point, it is our recommendation or
suggestion, at least starting out the gate, to use the following
settings unless you are knowledgeable in the actions of AGC
and it's affects in your particular operating environment.
To further add to this sticky wicket,
R01.08.10 mobile radio now have a new "noise suppressor"
function which may reduce audio by about 2 dB in some cases.
All in all, this effort is going to
be a monster to get correct will all the different types of
radios, microphones, voices and mic holding styles.
So, our bottom line, just please be aware of your audio, ask
for reports and compare other audio levels and let folks
know when they are very hot or soft relative to the other
audios in a given conversation. Some thought now given
to returning to AGC enabled and simply try to get people to
back away from their mics, though this is likely just going
to perpetuate the audio blasts that began this testing
episode.
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Gain |
AGC is
disabled and Noise Suppression enabled! |
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+5 dB |
HT's: all around
use; 2" @
45 degrees typical |
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+7 dB |
HT, with
speaker mic exclusively;
2" @ 45
degrees typical |
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+4 dB |
Mobiles
with standard mics;
2" @ 45
degrees typical
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+2 dB |
Mobiles with
Impress Touch
Tone mics;
2" @ 45 degrees
typical
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0 dB |
Mobiles with
Impress Base mics;
12" from mic,
typical tabletop use when seated, not closer
than 2" |
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Lower overall gain
setting if you tend to close talk,
have a loud voice or in a noisy environment.
If using 8.10 firmware in mobiles, please
see the notes. |
With so many repeaters and networks now
linked together, there is more range in audio levels now
being heard. One of the primary issues in audio levels
is the AGC's tendency to produce super hot (PIERCING) audio
levels briefly at the beginning of a voice encoding.
It is quite obnoxious and makes it difficult to monitor the
traffic on the network, especially when listeners are in a
mixed-mode environment of family, work or TV viewing, etc.
Less of an issue but still valid, is simply the wide range
of user voices differences and how the mic is positioned
relative to the mouth. Also significant though short
term or random, are issues such as breath puffs across the
face of the mic, wind and ambient noise.
While AGC works well most of the time for
most people, those lesser times are bad enough to force us
to look at options. Hence, the recommendations above
and our less than scientific method testing results below. If you have any
input, we always appreciate the comments, corrections and/or
suggestions:
Email us
Some users have stated they use settings
as low as -5 dB. Our settings above are the HIGHEST
recommended. Feel free to lower your settings if that
fits your normal uses better. TRBO radios have very
high speaker volume capabilities, especially the HT's
considering their size, so erring on the low Tx audio side
is preferred at this point. We would prefer to advise
you to increase your audio rather than be blasted by the AGC
fast attack times.
Details on the initial testing session
with different radios and microphones
NOTES: A HT was used for the Rx audio and VU meter
which was calibrated for +3 dB for Touch Tone 5.
The TT level doesn't change when changing mic level or
AGC enabled or disabled so that was a baseline which
anyone can use for relative testing. As TT levels
are normally set at 2/3's of max dev for the channel
bandwidth, the +3 dB VU was a reasonable target to get the
audio down to.
Testing was done using all R01.08.xx
firmware with AGC enabled, then disabled with gain
levels set at +7 dB (TRBO default) and +4 dB using the
internal mic on the HT. Next, using a mobile with
the standard compact mic, then the Impress Touch Tone
mic and lastly the Impress base mic. TT and base
mics typically in the Motorola line are very
hot and tend to hear that pin fall to the floor from
across the room so comments are included in this almost
anecdotal test method. If this topic
seems worth more effort, I maybe try using a Sinadder 3
to interpret the TRBO audio as a supplement the VU
meter readings. For now, waiting for feedback on
what is currently here.
XPR-6500 HT (R01.08xx)
AGC enabled: normal
voice averaged +4 dB VU but easily went into the red +12 VU and distorted if I close talked the microphone.
My normal is 2-3" away and no direct breath puffs,
all of which is problematic to maintain and provides
the AGC opportunities to emit those piercing blasts
of audio.
AGC enabled, Speaker/Mic: +
3dB VU, 2" and 45 degrees, easy to go into red when
close talking or directly facing mic to mouth.
AGC off, +7 dB gain: About
the same as AGC enabled, easier to over drive but
less likely the piercing blasts at the start of
voice (compression ramping up when AGC is enabled).
AGC off, +4 dB gain: Normal
audio average was 0 dB VU when speaking 1" away from
the mic, much harder to drive the radio into the red
but could easily do that if I talked directly into
the mic fairly loudly or blowing into the mic but it
took affirmative effort and not likely to been
done inadvertently.
AGC off,
Speaker/Mic, +7 dB gain: VU -4 dB VU, 2" and 45 degrees, about 0 dB VU close talking at
45 degrees, likely OK if you close-talk, less
background noise in noisy areas.
AGC off, Speaker/Mic, +4 dB gain: -12
dB VU, 2" and 45 degrees,
0 dB VU when close talking and/or
using louder voice, this
for noisy environments. XPR-4500 Mobile (R01.08xx)
AGC enabled, Standard Mic:
+4 dB VU, normal voice about 2" out and 45% to mic.
Easy to drive into the red though seems slightly
less susceptible to that nasty piercing tendency.
Also mic slots face downward so holding the so
that you speak from above helps a bit and is fairly
natural to do that anyway.
AGC disabled, Standard Mic, +7dB:
+2 dB VU, normal voice at 2", all else about the same
though less likely to be piercing than the HT's.
R01.08.10 noise suppression enabled reduced audio
about 2 dB.
AGC disabled, Standard Mic,
4dB: +0 dB VU, normal voice at 2", all else
about the same. R01.08.10 noise
suppression enabled reduced audio about 2 dB.
AGC enabled, TT Mic:
About +3dB VU, interestingly, about the same audio
level as the standard mic and even slightly
less susceptible to breath puffs. My
experience anecdotally with these Impress mics
is that they are hot and be like Motorola base mics
that have that tendency to pick-up the drop of a
pin.
AGC disabled, TT Mic, +7
dB gain: +6 dB VU, at normal voice 2" away,
45 degrees. R01.08.10 noise
suppression enabled reduced audio about 6-10
dB. A wild variation, I double checked
this and cannot account for the large swing.
AGC disabled, TT Mic, +4 dB
gain: +2 dB VU, at normal voice 2" away, 45
degrees. R01.08.10 noise suppression
enabled reduced audio about 2 dB. 6-10 dB.
A wild variation, I double checked this. A
wild variation, I double checked this and cannot
account for the large swing.
AGC enabled, Base Mic:
+2 dB VU, at about 8",
again surprisingly low though the base mic tried to bring up the levels
more noticeably than the TT or standard
mic as is typical of Motorola desk mics.
2" easily put the VU into the red. 12"
back averaged almost 0 dB.
AGC disabled, Base Mic,
+7 dB gain: +6 dB VU, normal voice at about
12". R01.08.10 noise suppression
enabled had no change.
AGC disabled, Base Mic,
+4 dB gain: +2 dB VU normal voice at about
12". Still can hit the red at 2" but lots
of control by voice loudness or moving
closer to the mic. 0 dB may be better
for some. R01.08.10 noise suppression
enabled had no change.
User
Comments: Other users have
reported good operation with these settings.
Remember, users voices and position to the
mic tend to fit that user more so than the
norm. But we still want to provide
this information for a more informed user.
Base
Mic on a 43xx: -15 dB gain, audio soft
but worked well at 2" and much less ambient
noise.
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