Is the echo on one side or both parties?
Echo can be a b... problem of the SPA is that the PSTN is passed on to the Line1. Having said that it converts the call twice
. Once to voip and than back to analogue.
Try this (sounds agains all odds).
Disable all echo cancellation:
Echo Canc Adaptive Enable = No
Echo Supp Enable = No
Echo Canc Enable = No
Set the FXO port Impedance on the PSTN tab to 220+820||120nF and set FXS Port Impedance to 220+820||115nF as a starting point
Set the spa to use prefered codec only (in this case it is G711)for the PSTN line, but for the LINE 1 set it to no (this reduces latency).
If you hear still an echo, your "power" is tho high (same as with the radio). Try what MirZab said, but do it slowely in increments of 3.
Try to SPA to PSTN first (this is for outgoing)
If you enable Echo Supp Enable, you will negate these parameters. The Sipura echo suppression is just an automatic gain control and it is recommended that it be kept disabled.
if the receiving party gets an echo, your phone might be to loud.
You can also try to fix the Impedance, if the hone and the SPA have a difference you can introduce echo aswell. Try to chang the FXS impedance to some other setting (eg 600) do the same for FXO port in regional.
Start with that, let us know how you go :-0.