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noahisaacmiller at gma...
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 Posted: Thu Jun 05, 2008 11:43 pm Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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Hi All -
I hope somebody can clarify for me what exactly fxotune does, and how
it is related to gain settings. I've been reading what appears to be
conflicting information from various sources.
I've got a box with an AEX800 with 6 lines (from Qwest) running
asterisk and zaptel versions 1.4.20.1 and 1.4.11 respectively. We've
been experiencing some echo/quality issues on certain calls which seem
to happen on all 6 of the lines. I manually calibrated the
rxgain/txgain using ztmonitor and a milliwatt test line to the
somewhat improbable levels of +10.0/-2.0 (about the same for all 6
lines). These settings yield acceptable call volumes, but echo and
noise are problems.
If I run fxotune, it gives me the following numbers:
1=10,0,0,0,0,0,0,0,0
2=12,0,0,0,0,0,0,0,0
3=12,0,0,0,0,0,0,0,0
4=10,0,0,0,0,0,0,0,0
5=10,0,0,0,0,0,0,0,0
6=10,0,0,0,0,0,0,0,0
Two questions here:
1) What do these numbers mean? Are they in any way related to either
rxgain or txgain?
2) Am I supposed to set rxgain and txgain back to 0 if I use fxotune -s?
If I do use these fxotune settings and set rxgain and txgain to zero,
the volume on incoming zap calls is almost too low to be heard, but
echo issues seem to be solved.
Do I have to choose between 1) acceptable call volume with echo or 2)
super-quiet call volume without echo? Should I petition Qwest to
install a repeater?
Thanks,
Noah |
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matt at mattgwatson.ca
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| Posted: Fri Jun 06, 2008 7:20 am Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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In short, fxotune adjusts line impedance, where as adjusting gains I believe
is essentially adjusting the amplification / deamplification of the signal.
http://www.voip-info.org/wiki/view/Asterisk+fxotune
--
Matt Watson
http://www.mattgwatson.ca
On June 6, 2008 12:43:51 am Noah Miller wrote:
| Quote: | Hi All -
I hope somebody can clarify for me what exactly fxotune does, and how
it is related to gain settings. I've been reading what appears to be
conflicting information from various sources.
I've got a box with an AEX800 with 6 lines (from Qwest) running
asterisk and zaptel versions 1.4.20.1 and 1.4.11 respectively. We've
been experiencing some echo/quality issues on certain calls which seem
to happen on all 6 of the lines. I manually calibrated the
rxgain/txgain using ztmonitor and a milliwatt test line to the
somewhat improbable levels of +10.0/-2.0 (about the same for all 6
lines). These settings yield acceptable call volumes, but echo and
noise are problems.
If I run fxotune, it gives me the following numbers:
1=10,0,0,0,0,0,0,0,0
2=12,0,0,0,0,0,0,0,0
3=12,0,0,0,0,0,0,0,0
4=10,0,0,0,0,0,0,0,0
5=10,0,0,0,0,0,0,0,0
6=10,0,0,0,0,0,0,0,0
Two questions here:
1) What do these numbers mean? Are they in any way related to either
rxgain or txgain?
2) Am I supposed to set rxgain and txgain back to 0 if I use fxotune -s?
If I do use these fxotune settings and set rxgain and txgain to zero,
the volume on incoming zap calls is almost too low to be heard, but
echo issues seem to be solved.
Do I have to choose between 1) acceptable call volume with echo or 2)
super-quiet call volume without echo? Should I petition Qwest to
install a repeater?
Thanks,
Noah
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noahisaacmiller at gma...
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| Posted: Fri Jun 06, 2008 9:11 am Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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Hi Matt -
Well, that clears it up a little. I think where I get confused is
that sometimes using fxotune is called balancing the hybrid and some
times using ztmonitor and adjusting the txgain/rgain settings is
called balancing the hybrid. Perhaps they both try to achieve the
same goal, but through different means?
This leads me to my other question - Are these two techniques mutually
exclusive? In some posts from Matthew Frederickson, it seems that
they are, and that if you use fxotune, you should set your gains back
to zero. Some other people seem to suggest using both fxotune and
adjusting gain levels. I note that Stephen Bosch asked just this
question some time back, and nobody was able to answer him.
Does anybody know?
Thanks,
Noah |
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creslin at digium.com
Guest
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| Posted: Fri Jun 06, 2008 12:21 pm Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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Noah Miller wrote:
| Quote: | Well, that clears it up a little. I think where I get confused is
that sometimes using fxotune is called balancing the hybrid and some
times using ztmonitor and adjusting the txgain/rgain settings is
called balancing the hybrid. Perhaps they both try to achieve the
same goal, but through different means?
|
Not quite. Gain adjustment affects volume levels of the respective
direction you are adjusting (echo and all). Balancing the hybrid via
fxotune attempts to balance the hybrid in a manner so that the hybrid
will remove as much of the echo as possible.
| Quote: | This leads me to my other question - Are these two techniques mutually
exclusive? In some posts from Matthew Frederickson, it seems that
they are, and that if you use fxotune, you should set your gains back
to zero. Some other people seem to suggest using both fxotune and
adjusting gain levels. I note that Stephen Bosch asked just this
question some time back, and nobody was able to answer him.
|
These techniques are not mutually exclusive, I usually want people to
use gain modification as the last step in trying to eliminate echo
(after balancing the hybrid and making sure you are using a good echo
canceller).
In the case of running fxotune, your zapata.conf software gain levels
should not affect its operation. If you are using any of the hardware
gain settings (wctdm24xxp module parameters) you should normalize those
to 0 beforehand so that they do not interfere with the calibration process.
--
Matthew Fredrickson
Software/Firmware Engineer
Digium, Inc. |
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noahisaacmiller at gma...
Guest
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| Posted: Fri Jun 06, 2008 2:37 pm Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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Hi Matthew -
| Quote: | These techniques are not mutually exclusive, I usually want people to
use gain modification as the last step in trying to eliminate echo
(after balancing the hybrid and making sure you are using a good echo
canceller).
In the case of running fxotune, your zapata.conf software gain levels
should not affect its operation. If you are using any of the hardware
gain settings (wctdm24xxp module parameters) you should normalize those
to 0 beforehand so that they do not interfere with the calibration process.
|
Thanks for your responses!
I actually didn't realize there are hardware gain settings available
for wctdm24xxp (is there any documentation on this? I can't seem to
find any). I assume the hardware gains default to 0 if left unset?
Just two more questions:
1) I think we were experiencing ECFO with an rxgain setting of +10db
(after having balanced the hybrid using fxotune). I'm guessing this
is because that rxgain value amplifies the echo a bit too much. I
know this is a bit of a loaded question, but is there a certain range
of values for rxgain/txgain that we should stay within in order to
avoid exacerbating any echo issues?
2) Are rxgain/txgain values applied before or after hardware echo cancellation?
Thanks,
Noah |
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creslin at digium.com
Guest
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| Posted: Sat Jun 07, 2008 10:12 am Post subject: [asterisk-users] fxotune vs rxgain/txgain |
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Noah Miller wrote:
| Quote: | Hi Matthew -
| Quote: | These techniques are not mutually exclusive, I usually want people to
use gain modification as the last step in trying to eliminate echo
(after balancing the hybrid and making sure you are using a good echo
canceller).
In the case of running fxotune, your zapata.conf software gain levels
should not affect its operation. If you are using any of the hardware
gain settings (wctdm24xxp module parameters) you should normalize those
to 0 beforehand so that they do not interfere with the calibration process.
|
Thanks for your responses!
I actually didn't realize there are hardware gain settings available
for wctdm24xxp (is there any documentation on this? I can't seem to
find any). I assume the hardware gains default to 0 if left unset?
|
Correct. They are set as module parameters, and actually only apply to
fxo modules.
| Quote: | Just two more questions:
1) I think we were experiencing ECFO with an rxgain setting of +10db
(after having balanced the hybrid using fxotune). I'm guessing this
is because that rxgain value amplifies the echo a bit too much. I
know this is a bit of a loaded question, but is there a certain range
of values for rxgain/txgain that we should stay within in order to
avoid exacerbating any echo issues?
|
I couldn't give you exact numbers off the top of my head. It's not hard
to notice though if it's happening 
| Quote: | 2) Are rxgain/txgain values applied before or after hardware echo cancellation?
|
rxgain is pre-hardware echo canceller and txgain is post hardware echo
canceller. (zapata.conf rxgain and txgain).
--
Matthew Fredrickson
Software/Firmware Engineer
Digium, Inc. |
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