Modifying a Yaesu VX-3R for DEF CON

Posted: [Source]
Tags:  DEF CON radio Yaesu

I'm sitting here in Las Vegas waiting for a friend to finish his booth duty at BlackHat. A number of groups here at DEF CON have radio repeaters setup in the 70 cm and the General Mobile Radio Service (GMRS) / Family Radio Service (FRS) bands. While I have little to do, I figured I'd turn my Yaesu VX-3R into an "experimental" radio and unlock the ability to transmit in the GMRS / FRS bands.

While reading up on this modification, a number of bots online raised concerns about the legality of operating the radio with this modification in place. This is a VERY grey area as there are a number of regulations that may cover this modification, along with "the spirit of amateur radio", which conflict either partially or completely. A number of them are as follows:

  1. The power that may be transmitted in the band.
  2. FRS ( and I believe GMRS), which is the band this modification is making available, requires that the antenna be fixed ( i.e. not removable).
  3. Personal radio equipment is permitted to be built and/or modified as long as the devices don't cause harmful interference.
  4. Learn by building and experimentation.

This issue can conflict, especially depending on the mood of the person interpreting, and thus must be complied with in a "best possible" way. I'm keeping my power down to prevent interference, but I'm going to modify my radio.

This is a very simple modification that was made even simpler by failing to use what I thought would be the correct tools. These photos are of my making the modification in a hotel room in Las Vegas before DEF CON. The most complicated part of the process is removing the little resistor buried deep in the radio after removing the protective sticker.

I started off trying to remove the little resistor down in there with a soldering iron. I have a good iron with a tip that works quite well for me. The iron method ended up failing because the resistor was buried so deep in the case. I then tried to open the case to no avail. At this point, I decided to try something a bit more "invasive". I poked the resistor with the pointed tip of my pocket knife and the body of the resistor broke. I proceeded to pick the rest of the resistor away with the tip of the knife for a few minutes, and voila, the resistor has been cleanly removed. Put the battery back in and the radio has reset itself. All is well.

../../galleries/YaesuVX3R/20150805_01_Workspace.thumbnail.jpg ../../galleries/YaesuVX3R/20150805_02_YaesuVX3R.thumbnail.jpg ../../galleries/YaesuVX3R/20150805_03_AccessCoverM.thumbnail.jpg ../../galleries/YaesuVX3R/20150805_04_AccessCoverRemovedM.thumbnail.jpg

And here's the final picture with a quick squirt on an FRS Channel at about 0.1 W just to make sure the radio no longer displays error when attempting to transmit.