The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

can any one tell me how to install talkback on this radio

This might help.
http://www.radiomods.co.nz/forum/viewtopic.php?=&p=3159

thank you sir

or drop a fat little resistor across the grounds of the pa/ext spkr on the back solder side of the main pcb. changing your resistance changes the volume of your talkback. running a pair of wires in series with these to a switch will make it switchable as well.