W8SDZ@SIMTEL20.ARPA (Keith Petersen) (03/11/86)
This is a repost for those who missed it the first time around.
Band Expansion Modification For The IC-02AT
By LTC Steve Peter, CAP
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1. Remove back from radio (9 screws must be loosened).
2. Carefully remove radio chassis from front case by pulling out top of
radio and lifting slightly (to remove contacts from bottom case.)
Be extremely careful of ribbon cable and heat sink compound on power
amplifier module.
3. While leaving case of radio face down, there are two diodes visible
near top of case (diode range board sticks out a little from under
the tone board). The diode on the right should have the top lead
lifted by touching with a hot soldering iron. This can be
accomplished without removing any board since diodes extend just
from beneath top PC board. Leave other end of diode (which is under
the top board anyway) alone. The diode can easily be reconnected if
necessary. If you remove the wrong diode, the coverage range will
be reduced rather than expanded. If you do not desire to transmit
out of band, you may skip to the step that mentions adjusting the
VC.
4. Using wire cutters, snip the top lead of R182-470K ohm resistor
(yellow-violet-yellow). This resistor is next to IC-102.
5. Next, tack a wire on to pin 13 of IC-102 and run to ground
connection. I used the PTT ground near the switch. Dress wire to
avoid pinching. This now allows the transmitter to operate on any
frequency the VCO will cover.
6. Install radio chassis back into front cover. Leave back off
temporarily.
7. Carefully apply power to radio and enter a frequency on the 160 MHz
band. (I recommend the continuous weather 162.55 etc.)
8. With power still applied adjust slug on VCO (not the trimmer cap) in
a counter clockwise direction until receiver hears desired station.
This sets the upper limit of your range and is about 1/2 to 3/4
turns from where it was set before.
9. If you have a counter you can set the upper frequency you wish to
use and adjust the VCO until the counter reads proper frequency. (I
adjusted for upper frequency of 165 MHz and radio will still
transmit on 140 MHz which will cover all appropriate VHF
frequencies.)
10. This completes the modification. A few words of caution:
a. The radio is not type accepted for use in the commercial band.
b. Make sure you install the battery latch correctly on bottom of
radio, or battery will become permanently locked onto radio.
c. Tighten screws on bottom of radio snuggly. If they loosen
while battery is connected you cannot remove the battery.
(This has happened to many units and it would be prudent to
periodically check these screws to assure their tightness.)
d. If you do not adjust the VCO after the mod, the radio will
cover approximately 133 MHz to 155 MHz as it comes for ICOM.
That's it, KA0JRQ's tech files...
Relayed and edited by KG2U/Bill