Improve handheld audio?
 

I recently got two older Icom IC-2N HTs (2 meter) for use in decoding
APRS packet radio. Nice radios, but I get less than 10% of packets
decoded with either radio. Compared to 100% of packets using my Yaesu
VX-2R. I know the problem is not the decoder, but the radio audio,
and wondered if there is anything I can do to improve the Icoms.

(And, no, I do not have an oscilloscope.)

Mike