[asterisk-users] Asterisk, Linksys SPA-3000 echo

[Rich Adamson]

Dean @ INKnBITs wrote:
> Hi,
> 
> I have been looking through all the web sites about echo problems and how to
> solve them on the spa-3000, but I still have not managed to fix mine! I'm in
> the UK and have setup all the tones, port impedance to 370+620||310nF, had
> the echo Canc options on and off, turned down the SPA - PSTN gain until it
> would not even dial, still had the echo. It not a little echo, its enough
> you cannot really use it. (I have 3 units, and they all do the same)
> 
> I'm using the SPA to route PSTN calls to asterisk, then polycom IP501 to
> asterisk.
> 
> Hardware version: 3.0.0(1178)
> Software version: 3.1.3(GWa)
> 
> I have tried 3.1.10 and 2.0.13, but still have the same problem, the other
> party has a clear call, but I can hear myself as an echo.
> 
> Has anybody got these to work ok? If so, please, please, please could I have
> the settings you used, it's been driving me crazy for the last two weeks.

In the US, the spa3k has echo problems with pstn lines that are somewhat 
long, and with pstn lines that are based on some central office remote 
line concentrators.  The spa3k seems to work fairly well on short pstn 
lines, but I've not tried to figure out exactly how long a pstn must be 
before echo becomes a problem.

I know in my case (four pstn lines from two different CO's) the spa3k 
does not do a very good job with echo cancellation, and these lines are 
roughly 7,000 feet. At least one of the lines is via a remote line 
concentrator (from a more distant CO), and it too has issues.

I've spent a significant amount of time with a commercial transmission 
test set to identify the operational parameters around these lines, but 
that only provides a perspective as to length, loss, etc. I gave up on 
the spa3k's as well as the TDM400, and installed a A200d. That has been 
providing excellent audio and echo cancellation for roughly six months.