VHF Marine Band and Out of Band (“Freeband”) CB Radio Modifications

Proviso: The following is for informational purposes only. Do not modify radios as described unless it is a dire emergency. (FCC regulations do not permit out of band transmissions except under emergency situations.)

One aspect of preparedness that is often overlooked is secure radio communications. As I’ve mentioned in some of my previous blog posts, buying a pair of VHF Marine Band radios makes sense if you live in an area that is both inland from the coast and away from the Great Lakes. You will essentially have a band all to yourself. Another approach to increasing communications security is modifying CB radios to transmit just above or just below the designated Citizen’s Band.(The so-called “Freeband”.) Although your transmissions will still be vulnerable to interception with any scanner, they will not be noticed by anyone that has a standard (unmodified) CB radio. Freeband modification was very popular in the U.S. back in the late 1970s and early 1980s when Citizen’s Band was very crowded. It also had some popularity in Australia.

The earliest CB radios used crystals. In those days you could order specially cut “bastard” crystals to give your the ability to transmit out of band. But very few of those radios are still on the market. Then along came the early synthesized CBs. These could be modified for freeband by clipping wires or soldering-in a few jumpers. (Some modifications were very clever. In one instance a panel light switch became a freeband toggle so that the freeband modification was un-noticeable to the casual observer.) The latest production CBs are also synthesized, but have virtually all of their frequency-setting electronics burned onto a chip. So those are not easily modified for freeband.

Many of the early synthesized CBs from the 1970s/1980s “golden age” of CB radio are suitable for out of band modification. One of the most popular of these is the Cobra 148GTL. (BTW, lots of other Courier, Galaxy, GE, Midland, Realistic (Radio Shack), Uniden, and President brand CBs from the same era can be similarly modified.) There is a lot of information on the WWW if you look around. Books like the CB Hacker’s Guide also describe these mods in detail. You will occasionally find a CB that has already been modified up for sale on eBay. But to be sure that a freeband mod is done right, your best bet is to find a standard Cobra 148GTL (or similar) with “low hours” and do the modification yourself.

In closing, I need this admonition: Do not be tempted to install a linear amplifier for illegal transmission in excess of five watts. That would be like waving a red flag to the FCC. Remember: “The nail that sticks up gets hammered down.”