IC-706 MKII Extended Tx Modification

21 Comments
Expanding the transmit range of an amateur radio transceiver is probably the most common modification. Because of its use associated with the Military Auxiliary Radio Service (MARS) or Civil Air Patrol (CAP), this modification is often referred to as MARS or CAP mod. This article shows how to perform this extended transmit modification on the Icom IC-706 MKII.

Asides from participating in MARS or CAP activities, there can be plenty of different reasons to extend the transmit frequency range of an amateur radio transceiver. I for instance, like using my amateur radio gear as signal generator for various experiments. A few days back, I got an IC-706 MKII in to perform the MARS / CAP modification on it. To my surprise, many online instructions on how to do this were either presenting the outdated main-board or poor graphics. So here’s the high-resolution instruction for the newer versions of the IC-706 MKII with main-board (B5209Q).

First off, one word of advise. If you have problems working with surface mount parts, this modification is not for you. The one diode that needs to be removed, is extremely small. How small you ask? Well, take a look:

Comparison of diode D2030 next to a cent coin

Comparison of diode D2030 next to a cent coin

To get to the diode, set the IC-706 on the table (LCD facing forward), remove the lid, and disconnect the speaker. You should now see the following:

The main board of the IC-706 MKII

The main board of the IC-706 MKII

In the top right corner of the main PCB is the diode D2030 that needs to be removed for an extended transmit frequency range. Here’s the close-up view:

Diode D2030 (red circle)

Diode D2030 (red circle)

Simply remove the diode and re-assemble the IC-706. Yes, that’s it. The removal of a single diode will convince your radio to transmit out of band.

Diode removed

Diode removed

Please cite this article as:
Westerhold, S. (2013), "IC-706 MKII Extended Tx Modification". Baltic Lab High Frequency Projects Blog. ISSN (Online): 2751-8140., https://baltic-lab.com/2013/09/ic-706-mkii-extended-tx-modification/, (accessed: December 15, 2024).

Sebastian Westerhold
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21 Comments

  2. Does this mod allow for transmit in the FRS freq range? I would think it might since it’s only about 12MHz above 70cm, but I could be wrong. I’m curious because I’m getting ready to buy a 706mkiig and that added feature would be nice.

    Reply

  4. Rob

    Thank you for this Info, It def helped me out. I did both the Fan mod and the TX mod, works great !! Radio also runs cooler.. 73

    Reply

  5. james VARNES

    I bought a car in a estate sale and in the trunk was mounted an icom 706mk2-a s#4418 and a at-180 a- tuner, the face plate was gone when I got the car, I have the remote wire and all the jumpers from the radio to the tuner.do you know where I can get another front peice for the706, I would also trade the tuner for it or pay cash. Thanks, Jim #863-412-6318

    Reply

    • Steve

      Keep in mind,you risk your Radio Amateur license if you get caught using non-type accepted radio equipment on 11 meters as well as FRS/GMRS. The IC-706 is not type accepted for out of ham band operation. MARS operation does not require type accepted radios.

      Reply

    • mike

      that is illegal as well as the FRS band another mentioned above
      & the radio will actually engage a 20db attenuator on that band when done which renders it useless

      Reply

  7. Derek

    I am not confident enough to do this modification by myself. Are there any service companies that I could send my radio out too?

    Reply

  10. Jeff

    The pictures in this mod are of a IC-706MKIIG, not the IC-706MKII. The two models have different main boards that are layed out differently. The MKII mars mod is the diodes just above the CP3 point and to the right of the J25 indicator where the two diodes are placed vertically, it is the one on the left that needs to be removed.

    Reply

  11. Graham

    I bought mine secondhand, it’s wide banded. Strangely it has two problems. On 18m band only I cannot adjust the power below 60W, my licence allows only 10W! On 20m power set to level 2 (10W) I get 10W on first click of mike, with a second click shortly after it shouts at 60W only on this band. Anyone else aware of this or is it just my unit?

    Reply

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