I found another way of modification for IC-2330. After the modification, we can receive;
This way might be more difficult than yours, but it is easy.
First, a switching diode should be put on the circuit board in the circle on this picture.
Second, the transceiver should be reset. To be reset, turn it on with pushing [SET]+[MW].
And turn off and turn it on again with [V/M]+[SET]+[DN]. [DN] key is located on microphone.
That's all of modifications for IC-2330.
In addition, if you want to put an external antenna for 830-950MHz, put coaxial cable in the circle on this picture.
This mods is shown in a web page in Japan. That means it wouldn't work well coz this mod is for IC-2330 sold in Japan.