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123 posts

Master Geek


# 12363 13-Mar-2007 17:40
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Hi,

I was having some horrible echo on PSTN calls. It took me ages to locate the problem and the solution -- it was my SPA3102.

I just thought I'd post this here, because this seems to be a simple solution when you know what you're doing, and I hope it helps others find the solution more quickly.

From http://www.voip-info.org/wiki-Sipura+3000

  • The echo canceller in the SPA-3000 is very basic and limited to an echo tail length of 8ms. It may take 15-30 seconds for the SPA-3000 to "converge" on the proper cancellation values for a call. Long PSTN loops or cellphone calls may suffer from uncorrectable echo with an SPA-3000, in which case the only solution is to buy an FXO gateway with a better echo canceller. - bani

  • Echo Supp Enable (PSTN Line) may produce very poor quality PSTN calls, as this setting dynamically adjusts gain based on sending and receiving audio levels. Volume may jump around and callers may find their sides being squelched in a CB-halfduplex-style. If you are willing to tolerate some echo while the SPA-3000's echo canceller converges during a call, you can disable this for much better overall PSTN call quality. - bani

  • In many cases the outgoing PSTN audio (SPA To PSTN Gain) is "too hot", leading to distortion that no echo canceller is able to handle. Lowering this by several db may help alleviate some PSTN echo issues. -6 is a value which works well for me. - bani


The thing that worked for me was the SPA to PSTN gain. The default was 0. I set it to -6 and Bob became my uncle.

Rob

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450 posts

Ultimate Geek


  # 64171 18-Mar-2007 16:15
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i had similar problems with my SPA 3102. Before altering the gain try
altering the impedance setting . My setting in FXO port impedance is set to give the  best
result for me  is 270+750 150nf . I think the default is about 600 ohms but A setting   around 1100
seems to balance the 4W hybrid best. cheers George


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  # 64177 18-Mar-2007 17:12
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GEOMAX:
i had similar problems with my SPA 3102. Before altering the gain try
altering the impedance setting . My setting in FXO port impedance is set to give the best
result for me is 270+750 150nf . I think the default is about 600 ohms but Asetting around 1100
seems to balance the 4W hybrid best. cheers George



The correct line settings for NZ is 370+620|310nF using anything else will cause you problems.

This is detailed in the Telepermit specs.


 
 
 
 


450 posts

Ultimate Geek


  # 64202 18-Mar-2007 20:06
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The correct line settings for NZ is 370+620|310nF using anything else will cause you problems.

This is detailed in the Telepermit specs.

cable/line  impedance varies depending on such things as conductor size ,length etc and combined with the switch or PCM
card termination can give variations. I am suggesting if you hsve trouble with echo or low level tones ,vary the  impedance settings. This is based on my past work experience and optimizing my system at home. As Robscovell has found out....it sure as hell is no good with standard settings.

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