Popular Wireless Magazine

General Mobile Radio Service
Interstitial & FRS Frequencies

Interstitial frequencies are available for simplex use by all GMRS licensees. Operation on these channels is restricted to GMRS Small Base Stations and GMRS mobile units operating with five watts or less of effective radiated power. GMRS shares these channels with the hand-held radios of the Family Radio Service.

Radios for the Family Radio Service:

• are limited to one-half watt of effective radiated power.
• may not have removable antennas nor can the antenna that came with the radio be replaced or modified with any type of antenna other than the type it was designed to use.
• may not connect to external antennas to increase the range of operation.
• must be type accepted for use in the FRS.

GMRS licensees can establish a Small Base Station (five watts ERP or less) on shared Interstitial channels with an antenna that is less than 20 feet above the structure the antenna is mounted upon. GMRS equipment can communicate at considerably greater distances than FRS. Establishing a small base station for use in your immediate neighborhood can be an excellent alternative to sharing a busy GMRS channel used by repeaters.

Because no license is required for the Family Radio Service, some have declared the FRS frequencies the "free band." FRS users should remember that the band is in fact shared with stations that are licensed to operate on these frequencies. FCC restrictions on the type of equipment that can be used in the FRS are essential to minimizing interference.

There has been some interest on which channel might be considered a "travel channel, calling channel, or even and emergency channel." Since the range of a half watt radio is very limited the concept ONLY makes sense if you're within half a mile of the same vehicle going the same direction OR you are lost within a mile or so of an FRS station willing to help. Given those conditions it is probably best to try channel 1. I suggest you try saying something like, "travelers aid" anyone listening. Remember that FRS was NOT designed to provide emergency assistance. DO NOT expect to attract help in an emergency calling on any FRS channel. The best advice we can give is to carry a cellular phone.

(*)Many users of the Family Radio Service use channel one for general calling and move off to channels 2 through 14 for conversations. This channel is the most frequently used of all the FRS channels since Radio Shack markets their popular single channel units only on the frequency. Informally, some users have also talked about this channel as one where you are most likely to meet another another traveler. What that means to a very low power radio service is uncertain. You should not expect to buy these radios for personal travel assistance. A cellular phone is a better alternative. These radios are ideal for short distance communication to coordinate family events. Remember also that the first seven are shared with the General Mobile Radio Service.