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.
Step 1: Open the Radio to See the Main Board, and Back Display Board Too.
Step 2: Locate the Ht9170d Chip on the Main Board, Near to Conecctor to Display Board
Step 3: Locate the Mic Conector Exclusive Pin 8 and Install a Wire From This Pin to Ht9170d Chip
Step 4: Install One End of the 2,2uf Electrolitic Capacitor on Pin # 2 Ht9170d Chip (vn Pin) and Another Capacitor End to Wire From the Pin 8 of the Mic Connector
Step 5: The Mod Is Done!, Now You KT8900 Have a Audio Signal From the Discriminator on the Pin #8 (mic Connector)
Reesamble your radio and make wires to your PC Sound card
The signal is clean and strong to your audio input on the sound card