I would like to configure an icom 9100 to send packet through soundmodem. The icom is connected to PC1 through usb connection with a baud rate 19200. 

To check the transmission, i'm using rtl sdr dongle installed on PC2. The transmission is working fine when i use a manchester 2400/1200. When I increase the modulation to 4800, the sounmodem cannot decode the packet. When i send many times (30 packets), the sdr capture one packet with this speed. 

1. Please any advice?

2. Connectig the icom to PC1 through ACC connector can resolve the problem. If yes, please should I connect the acc to serial port or in/out jack (if you have any schematic to follow). 

Thank you in advance.

Kind regards

Kais