ICOM 02/03/04 & Vox Unit

The ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the

many available power supply options. The big problem is getting the PTT to operate " CLEANLY " while not

compromising the audio level from the TNC when using the resistor or resistor/capacitor interfaces suggested

in some manuals.

I am using the ICOM HS10-SA Vox unit to interface the ICOM 02/04 AT here.It has worked somewhat well

for some time but I was always plagued with a MINIMUM 200 msec transmit "hang " delay until I tore it apart

for examination and correction.

The small " delay " pot on the front of the unit is in series with a 2.2 Megohm resistor (R-19 on the board).

The adjustable pot is also about 2 megohms as well. This combination allows a MINIMUM VOX "hang" transmit

delay of 200 msec.

By identifiying the solder connections for R-19 on the back of the PC board and placing a low value resistor

( or jumper ) in parallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the

FULL COUNTER-CLOCKWISE position.

The minimum 200 msec delay has been defeated.