Yaesu FT-8800 Extended TX (MARS/CAPS) Mod

The Yaesu FT-8800 and FT-7900 are very popular radios. For some activities, it may be desired to be able to transmit outside of the amateur radio bands. This article will show how to do this modification with minimum effort at home.

Driving a transverter, participating in the Military Auxiliary Radio System (MARS) or Civil Air Patrol (CAP) are just three examples for which an out-of-band extended transmit modification can be handy. Since “out-of-band extended transmit modification” is awfully long, it’s colloquially referred to as “MARS/CAP Mod”.

The modification procedure is the same for the FT-8800, FT-8800R, FT-7900 and FT-7900R. I will use an FT-8800R to illustrate this article. After this modification is complete, the radios will transmit between 137 MHz – 174 MHz and 420 MHz – 470 MHz.

The mod itself is very easy. It simply consists out of removing a surface mount resistor and power-cycling the radio. The first step is to remove the top cover of the FT-8800. The speaker can be disconnected for more room, but in my case, I didn’t think this was necessary.

FT-8800 with opened cover

FT-8800 with opened cover

The second step is to identify the correct resistor. Be sure to double and triple check that you are removing the correct part. The following picture shows the exact position of the SMD resistor. Click on it to see the super large version.

Jumper location for the FT-8800 extended TX modification.

Jumper location for the FT-8800 extended TX modification.

Once you have identified the resistor, remove it. This can be a bit tricky if you don’t have the right soldering tools. A desoldering tool is certainly helpful, but different people have different ways of performing such tasks. One way is to add a small blob of solder to one side of the part and rely on heat transfer within the tiny part to get both sides loose. Some people just cut the resistor with pliers or a scalpel. The latter option can however damage the PCB and the traces.

After this step is completed, reassemble the radio and apply power. The radio will automatically perform a reset and will be able to transmit.

Startup screen of the FT-8800 indicating that the radio is resetting

Startup screen of the FT-8800 indicating that the radio is resetting

11 thoughts on “Yaesu FT-8800 Extended TX (MARS/CAPS) Mod

  1. Hello KF5OBS
    thanks for your discription about this modification
    I own a Yaesu FT 7900E (europe model)
    standaard the 2 meter bands is 144-146 Mhz and 430-440 Mhz
    I like to know if this mod also will work on a Yaesu FT-7900E version
    Because i like to use the part 446-447 Mhz to use our PMR channels on this rig

    73, de Cor
    PA0GTB

    • Yes, this absolutely works on the E versions. What may be different in the European version is, that there may be more than just one jumper set from the factory. For the modification you want to make sure that the end result looks the same (=no jumpers set at all). So it may be very possible that you may have to remove more than one jumper.

    • I also have a ft7900e i would like to know the complete mod for it . Please if you find the mod please let me know . Thanks .

  2. Be very careful with this model, the various regulators requested that all manufacturers reduce their band edges with open mars cap mod done, in this case the previous version went to 478.000mhz, this version 447.000mhz.

    When I did it to the Aus version, the radio stopped txing so had to send it to yaesu, how embarassing

  3. I did this mod on my ft-8800R using a hot air tool that was set at 700deg F and it worked out just like it should. No hangups at all and i am very happy that i can do mars/cap without having to buy another radio. the part is very tiny so be careful when removing and dont let it vanish in the radio and short something out at a later time. Please DO NOT do it the mickey mouse way because there is more of a chance to ruin your $400-$500 radio and that would suck.The hot air tool on a decent work station is the safe and easy way to do this mod.
    KK6HYY

    • I agree. If I do this (and other) mos for others through my business, i use a proper SMD rework station. However, most people at home prefer the method shown because they have insufficient hot air equipment at home.

  4. KF5OBS,

    What other functions does this mod affect? I know when you MARS/CAP a FT857/897 you lose the automatic repeater offsets. Does this happen here? Also how does the mod affect crossband repeat? Thanks in advance, N8RLG

  5. Will this work on the Yaesu 8900-R as i was sold there was a slight difference never tried doing it myself .

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