QYT KT8900 mod for PACKET
This is a chinese cheap 20W 144/440MHz mobile radio, but have two wrong design thinks to connect friendly this unit with your sound card because them not have a external speaker jack, also the squelch operation is too slow.
A good idea is take the audio signal from the discriminator directly, here you have a opensql signal, a clean and good quality and audio signal.
To make this modification please use the ht9170d chip (used to decode a DTMF signaling) also use empty pin 8 on the mic connector with a 2,2uf electrolitic capacitor to audio coppling.