Modifications for the ICOM - RogerK

19-07-1998(IC-03) ICOM 02/03/04 & Vox UnitThe ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supplyoptions.The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using theresistor 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 Iwas 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 isalso 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 ) inparallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISEposition. The minimum 200 msec delay has been defeated.This modification is read 462 times.top of page19-07-1998(IC-04) ICOM 02/03/04 & Vox UnitThe ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supplyoptions.The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using theresistor 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 Iwas 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 isalso 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 ) inparallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISEposition. The minimum 200 msec delay has been defeated.This modification is read 588 times.top of page19-07-1998(IC-04) Out of band modification for IC-041. On the logic matrix, remove D402.2. Add D402, D403 and D404 with the cathode at 4 o'clock and the anode at 12 o'clock. (You may use any signal diode suchas 1N914)3. Add D405 with the cathode at 8 o'clock and the anode at 12 o'clock.4. If you have a newer 04AT, the VCO cover will have holes in it that allow access to the tuning coils. If you have an older04AT you will have to cut a hole in the VCO cover using a pair of small diagonals (be careful!).5. Retune the VCO to cover your desired frequency spread. My 04AT goes from 441 to 473 MHz, which is pretty good.6. Any frequency may be entered directly on the keypad (starting with the 10 MHz digit).This modification is read 673 times.top of page