The Federal Communications Commission is cracking down on truckers who use license-only frequencies in their trucks.

The American Radio Relay League, an organization of ham radio operators, noted recently on its Web site that Riley Hollingsworth, special counsel of the FCC’s Enforcement Bureau, sent a letter to FedEx Corp. Chairman Frederick Smith.

The letter reportedly included a claim that some FedEx drivers used "amateur radio transmitters to communicate on the 10-meter Amateur Radio band without a license."

Hollingsworth reportedly asked Smith to advise his company’s drivers that operating equipment on those frequencies without a license is a violation of federal law and could lead to fines or jail time, as well as seizure of equipment.

Hollingsworth also reportedly asked two other trucking firms to contact him to discuss similar allegations.

The controversy has been simmering for some time. To use Amateur Radio, or ham frequencies, radio users must have a license. However, to use a CB, you do not.

The problem started when some shops started to sell truckers CBs that include ham frequencies, but did not tell the truckers they could not use those frequencies without a license.

Ham frequencies start just above where the highest CB frequency, listed on radios as channel 40, ends.