Date: Thu 9 Feb 89 12:02:25-PST From: Brad Horak Subject: Icom IC-900 mods To: MBramwel@business.uwo.ca Enclosed is a list of frequency range extension modifications for the IC-900. They are courtesy of KB1MZ and KA1OKQ. Some mods may enable out-of-band transmission. Transmitting there is ILLEGAL ! These radios are not type accepted so therefore it is ILLEGAL to use this radio out of the ham bands even if you have a license to do so. (ie volunteer F.D. etc). All mods are done at your own risk. This is in NO way an invatation to break the law. The mods are provided for information only..........................73 Gene WA1UXA Subject: Icom IC900 mods Frequency Expansion Modifications for the ICOM IC-900 All changes are made in the control head. Diodes are arranged in a 8x4 array: A-H, 1-4. As shipped from the factory, the diodes are arranged thusly: X = diode in place ____________________________________ | | X | X | | | | | X | 4 |---|---|---|---|---|---|---|---|--- | | X | | X | | | | | 3 |---|---|---|---|---|---|---|---|--- | | X | | | | X | | X | 2 |---|---|---|---|---|---|---|---|--- | | | | | | | | X | 1 |---|---|---|---|---|---|---|---|--- | A | B | C | D | E | F | G | H | To add recieve coverage on 6 meter and 70 cm bands only: C=cut diode, or remove ____________________________________ | | C | X | | | | | X | 4 |---|---|---|---|---|---|---|---|--- | | X | | C | | | | | 3 |---|---|---|---|---|---|---|---|--- | | X | | | | X | | X | 2 |---|---|---|---|---|---|---|---|--- | | | | | | | | X | 1 |---|---|---|---|---|---|---|---|--- | A | B | C | D | E | F | G | H | 440 Band - to expand coverage from 420 - 470 MHz: Remove diode D25 (3,D) for RX Install diode in (3,C) for TX VCO in 440 module covers a 20 MHz range - re adjust as needed. 220 Band - to expand TX coverage from 216 - 236 MHz: * This mod hasn't been tried and verified. * Install diode (1,C) for TX Remove diode (2,D) - ? 144 MHz Band - to expand TX coverage from 138 - 174 MHz: Install diode in (1,C) 50 MHz Band - to expand coverage from 40 - 54 MHz: Remove diode D32 (4,B) for RX Install diode in (4,A) for TX 28 MHz Band - to expand coverage from 28 - 40 MHz: Remove diode D32 (3,B) for RX Install diode in (3,A) for TX -------