Modifications for the ICOM - RogerK

I I 2 2 2 2 2 2 3 2 ---I I 2 5 3 6 4 7 0 8 all diodes : /-----IID22 : When soldered, Europe version, activate the 1750D25 : When not soldered, RX on VHF from 136 to 174 MHzD23 : When soldered, USA version, activate the Sub-tone on TXD26 : When not soldered, RX on UHF from 420 to 460 MHzD24 : ? who knows ?, not solderedD27 : When not soldered, TX on VHF from 136 to 174 MHzD30 : When soldered, activate the transponderD28 : When not soldered, TX on UHF from 420 to 460 MHzThe initial matrix on a US-820 (from D22 to D28) OFF ON ON ON OFF ON OFF ONon a European 820ON ON OFF ON OFF ON OFF ON4. to activate the 1750, remove the diode on D23 and put it on D30. You don't need to either reset the 820 or remove thebattery. You have now a quiet 1750Hz when you push the TONE button, and a standard Europe bandwith on VHF and UHF(144-146, 430-440 MHz)5. Now we need to boost the modulated 1750Hz, to do so, you have to short two resistors : R80 100k, located near J16,J1which is between R79 and R29. Also R17 1k, located near IC11, IC8.6. Now the level is near to correct. If you whish, you could trim with R64. It's an adjustable resistor marked STBN located onthe large printed circuit board on the bottom of the 820.Remember that you lose the capability of sub-tone on TX (CTCSS), but not on RX, if you have the optional module installed.What to say more ? It's works fine on my old-US-820 !!!Please leave me a message on my BBS, if you need more informations !73 de Francois HB9IBI @ HB9IAP.SROM.CHE.EU (old HB9RTE)This modification is read 741 times.top of page23-11-2001(IC-820) ICOM IC-820H extended receive/transmit modificationThis modification is to open the IC-820H for extended receive (and transmit) operation. This is a two (four) step modificationwhich will open the IC-820H to the following frequencies:VHF BandUHF Band136 - 174 MHz420 - 460 MHzThese frequencies are not guaranteed for accuracy or sensitivity.1. Remove Diode D25 on logic board for VHF RX Expansion.2. Remove Diode D26 on logic board for UHF RX Expansion.3. Remove Diode D27 on logic board for VHF TX Expansion. *4. Remove Diode D28 on logic board for UHF TX Expansion. ** RX modification must be done before the TX modification will work. *This modification is read 723 times.top of page23-11-2001(IC-820) ICOM IC-820H cross band repeat modification