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Amplifiers and Icom mobile transceivers

Using amplifiers with Icom "mobile" transceivers
The Icom "mobile" radios (the 703, 706 series, 7000, and 7100) have a modular ("RJ-45") mic jack and single 13 pin ACC connector while the "base" radios* have traditionally had a round ("Foster") mic jack with separate 7 pin (amplifier - ALC, send, "band voltage") and 8 pin (audio in/out, FSK, PTT In) ACC connections as well as separate RCA jacks for "Send" and ALC.  For the "base" rigs the microHAM audio in/out, FSK and PTT In connections use the 8-pin ACC connection leaving the 7-pin jack free for use with an amplifier.  However, with the "mobile" rigs the normal 13-pin ACC connection is used by the microHAM interface and prevents connecting an amplifier.
For the mobile rigs,  the alternative - and the one recommended by Icom - is to use the Icom OPC-599 "conversion cable" to convert the 13 pin ACC jack to separate 7 and 8 pin jacks (the OPC-599 is documented in the Instruction Manual of every Icom mobile transceiver).  If the user chooses to acquire and use the OPC-599, the DB15-IC-8 is used for USB Interface II/USB Interface III/DigiKeyer II and DB37-IC-599 is used for microKEYER II/MK2R+.
In most cases, users of USB interface II, USB Interface III, DigiKeyer, and microKEYER will need to acquire the Icom OPC-599 with DB15-IC-8 instead of the DB15-IC-13 or DB37-IC-599 instead of the DB37-IC-13.  Most amplifiers will also require a buffer circuit to interface amplifier PTT to the HSEND pin of the 7-pin ACC connection.  Since the Icom mobile rigs tend to drop HSEND before the end of RF (see: http://www.bnk.com/w0qe/amplifier_timing.htm) - at least in QSK CW, the buffer should be of a design that includes a "turn off delay" to prevent "hot switching" of the amplifier T/R circuits.  A suitable amplifier PTT buffer has been described by Phil Salas, AD5X on his web site (see: http://www.ad5x.com/images/Articles/QSKDelay.pdf).
For users of Digikeyer II and microKEYER II (only), if the amplifier to be used does not require an ALC connection (note: an ALC connection is strongly recommended with solid state amplifiers as 100W will typically result in overdrive and damage to the amplifier) and can be used safely with just PTT, the amplifier PTT can be connected to the PA PTT output in DigiKeyer II or microKEYER II as long as the "IC VOX" jumper is set properly (for VOX operation) and PA PTT Tail is more than 20 ms to prevent hot switching.
(*) Note: Some Icom transceivers (IC-78, IC-718 IC-7200, IC-7140, & IC-9100) combine a Foster (round) mic jack and 13 pin ACC connection. These transceivers also have separate RCA ALC and "SEND" jacks and do not require use of the OPC-599 and buffer cable with an amplifier other than the Icom PW-1.  The "hybrid" rigs use DB15-IC-13 for USB II/USB III/DK II and DB37-IC-718 for MK II or MK2R+.

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