ICOM 706 Mk II G
by N6GCE - Good Computer Engineer

Why the 706?

With my upgraded General ticket I wanted an HF  radio that:

Antenna for HF transmit & receive

Short Term

I will use my existing B&W 1.8 - 30 T2FD BWD-1.8-30.  This is a folded dipole with a termination on the far side from the balun.  It makes a great wideband receiving antenna.  On transmit it is not as efficient as other types of antennas.

I have not yet looked into an antenna for 2m & 400 - that's on a seperate connector.

Long Term

I a planning to use the Light Weight Beacon Part No. 123402 Antenna.  Instead of fixing the broken screw driven tuning slugs, I will replace the bottom section with a couple of feet of PVC pipe.  But first I need to trench and install 12 each 80' long ground radials and a connecting ring (about 1,500 feet of Cu wire).
Also a trench with conduit for the coax and control wiring to the antenna would be nice.
Then put up this 55 foot tall antenna that all fits into a back pack.

The SGC - SG-231 Smartuner® looks ideal for this antenna.  The manual (online at SGC) has instructions for interfacing the 231 to the 706 so that the "Tune" function works.  The 231 differs from the 230 in that the upper frequency limit is 60 MHz, thus it will work for HF plus 6 meters.

There is information on how to connect the 231 to the IC706 so that the "tune" function works properly.  The "smart tune PRO" accessory can also be used with the 231 to allow control of when the tuner attempts to tune.  Note that the normal smart tune accessory will not work with the 231, maybe because of a difference in the connectors, the 231 does NOT have the receive amplifier that's in the 230PRO.  There is also an option to allow receive operation in a straight through mode (no tuner like would be the case for ALE) or with the tuner working to improve reception at frequencies close to the transmit frequency.


Control Cable 
Acc Connector

+13.6 VDC in PIN 1  PIN8 13.8 VDC out
Option 2
Interrupt - Start ICOM Tune Sequence
Option 3
Bi-directional Data Line

Note that the 231 is an antenna Coupler not an antenna Tuner.  The difference is that a tuner (the military might call it a line flatter) is a device with coax inputs and outputs (maybe sometimes ladder line in/out).  It's job is to transform the impedance on a transmission line to 50 Ohms to match a transmitter output.   A coupler has a coax input form the transmitter but has a single terminal that has high voltage insulation because it drives a wire (NOT COAX) that is part of the antenna.  A coupler is preferred because the VSWR on the coax to the transmitter is low.  In the case of an antenna tuner the coax between the antenna and tuner has a high VSWR and hence high losses.  SGC has a lot of practical information on their web site about how to correctly use their antenna couplers.
 Exl Ctrl Wires 
 Ext Ctrl Conn 
 Internal Header 
Red J1 -1 J10-1 13.8 VDC Power
Black J1-2 J10-2 Ground
Green J1-3 J10-3 Tuned Indicator
Blue J1-4 J10-4 Reset the coupler
White J1-5 J10-5 Hold (Locks coupler settings)
Brown J1-6 J11-1 VHF 
?possible future enhancement, idea that did not work, who knows?
Violet J1-7 J11-2 Option 2 (Option B) = Interrupt - Start ICOM Tune Sequence
Orange J1-8 J11-3 Option 3 (Option A) = Bi-directional Data Line

The Internal Jumpers are:

The Smart Lock Pro has a cable with the folowing wires:
  • black&shield:    Ground
  • Red:                  J1-1, Red   13.8 VDC
  • Green:               J1-3, Green, Remote Tuned Indicator
  • White:               J1-5, White, Hold Settings (Tune Lock)
  • Brown:             J1-Not Used (this is the VHF function?), labeled Rx amp for use with the discontinued SG230Pro tuner
  • Blue:                 J1-2, Black, Ground

  • There is a new model SG237 that is a 1.6 - 60 MHz design that is smaller and lighter than the 231.  It has one less inductor and one less cap on the output for 1/2 million combinations vs. the 4 million for the 231.  The 231 is also rated for more power.  It's not clear about the connectivity to the IC706 "tune" function.
    The 231 is directly supported.  The lower frequency rating on the 231 is 1.0 MHz vs. 1.6 for the 237.  The 237 comes in the normal type box and also as a raw PCB and the third variation is mounted in a box that matches the SG2020 transcivier.  The 237 only draws about 300 ma and the 231 about 500 ma?

    (I tried to get one of the 230PRO models, but they have discontinued it,  note this is NOT the same as the 230 Smartuner®!  The Pro version has the ability to interface to a computer, my kind of a product.)  If anyone reading this has a 230PRO I would like to hear how it works. brooke@pacific.net

    Very Long Term

    The next step may be to try to put together some kind of time delay beam steered array of antennas.

    13.8 VDC Power Supply

    In order to power either the IC 706 (13.6 VDC @ 20 A) or a PRC-47 (28 VDC @ 20A) I came up with the idea of using a 12 volt deep cycle storage battery and a line powered 12 VDC supply.  The Astron SS-30M switching mode supply weighs only 5 pounds and includes a volt & amp meter.  The SS-30M is about the same size and weight as the 706 so I have the 706 sitting on top of the SS-30M.  In receive mode the 706 draws less than 2 Amps.  The quiet fan on the SS-30M turns on and off every now and then.

    My old linear 13 Amp 28 Volt supply weighs about 40 pounds and is not strong enough to power the PRC-47.  It turns out that with the metering on the SS-30M that the PRC-47 could be powered by my older supply in the low power mode.  There is a problem with the PRC-47, not the power supply.

    The battery was on sale at Wal-Mart and is marked as a trolling battery, 115 AH.  I am now working on the system of connectors to accommodate powering either of the two radios in many optional ways, as well as many 12 VDC items like GPS receivers.  Note that the SS-30M has an internal strap between the black negative output terminal and the case & line grounds.  This was added because some users had problems with RF interactions.  I have lifted the PC board end and shrink tube insulated it so that the supply can be used in a floating mode because I plan to ground the negative terminal of the 12 volt battery.

    I am using 6-20 connectors that the local hardware store has in stock.  These are rated 250 V @ 20A.  They have a ground terminal like on U.S. household grounded connectors but one of the blades is turned 90 deg. from normal and the other is a "T" shape.  This will prevent anyone from plugging a normal AC type plug into the DC sockets. I am using the "-" terminal for 12 VDC and the "T"  for 24 VDC, with the ground terminal for ground.  Note that there is a 5-20 connector that looks very similar but has a different arrangement of terminals. For power sources like the battery and charger the socket is used.  For loads like radios and inverters the 6-20 plug is used.  This is the same convention used with most power connections so that it is less likely to have a short.

    The battery will be charged and maintained by the Statpower - TC-10hw (Statpower calles it the TC-10tb, terminal block) smart charger.  This is a mocroporcessor controlled charger made for marine use. The hw model is for hard wiring and can support two independent battery banks.  It's a 10 amp unit but will charge faster than some higher amp units because of the smart nature of the charge.

    Circuit Drawing DC.dwf  (Free Volo or WHIP! Viewer from Autodesk).
    Xantrex (Statpower, Heart, Trace & Cruising Equipment combined)

    Computer Control

    The computer control commands for the IC706MkIIG are on pages 45 & 46 of the owners manual.
    The CI-V Reference Manual p/n 99900001 $15/ea. has a comprenhsive coverage of the CI-V interface with sheets added for the:
    8500A, 755DSP, 820H, 821H, R10, 706, 706MkIIG, 746, 756.


    ICOM706 web page 800 USA-ICOM (800 872-4266)

    Vartel's ICOM 706 Discussion Group - many common questions & answers
    706 Mk IIG - Mil Radios for ham use -

    Klamath Amateur Television  - VC-H1 SSTV to 706MkIIG -

    direct frequency entry keypad - December 99 QST by John Hansen

    Communication Outfitters - FT-817 back pack and portable antenna

    QRZ.COM - Radio Modification Files - ICOM IC-706 MK II G TRANSMIT MOD - with color photo

    PC-ALE Project by Charles H Brain G4GUO - supported radios (June 2000 ): IC706, IC746, FT757, FT1000MP, TS850, Ten-Tec Pegasus
    WUN - ALE Information - includes a FAQ/Manual for the G4GUO program

    PSK31 "Official" Homepage - by Eduardo/EA2BAJ
    Fuzzy Modes Web Site by Murray ZL1BPU Greenman -
    G3PLX Chirp Project - Peter Martinez G3PLX (also inventor of PSK31) or http://www.qsl.net/zl1bpu/chirp/chirps.html

    Remote Operation of Station - KM07KS - uses DTMF-8 Touch Tone interface
    TRX-Manager - F6DEX - software to control a list of radios
    6m Vertical Antenna by Mike, G3JVL

    Back to Brooke's home page, NRD-545 page, HF propagation page, RCS-5A chirp sounder page, EVM56002 Chrip page
    This is the  time this page has been accessed since 7 June  2000.