Aerial Video Services, out of Burbank, California, is major supplier of the in-car cameras, wireless cameras and communications links for the television coverage of auto racing and other sporting events. During a recent racing series at the Texas World Speedway, AVS provided the microwave and communications equipment for the Prime Network television coverage of the races. I had a chance to work with the AVS crew, and check out their radios. If you get to attend a sporting event where wireless cameras or mics are in use, you might check out some of these frequencies. Let me explain a little about the equipment they are using, and what you might hear. Any time there is a wireless camera in use, they will be sending the pictures from the roving camera location to the TV remote truck on a microwave link. They may use the 2 to 2.5 gHz or 7 gHz microwave bands. In addition to pictures from the camera, there has to be voice communications to the cameraman, and sound from the announcer's microphone, who may appear on camera, and a cue channel to the announcer, so he knows when he is on the air. The communications from the TV director to the cameraman are usually referred to as the "PL". This stands for "party line", and is a two-way communications link with the director and the camera operator. It is usually set up as a low-power repeater, so you will always hear the directors calls, and the camera operators replies. The cue channel to the announcers is called the "IFB", which stands for "interrupted feed- back". This is usually the audio from the program that is being produced, along with the director or producer interrupting the program feed, in order to give cues to the announcers. This transmitter will be on as long as the TV production truck is operating. AVS uses mostly I-COM programmable radios. Here are frequencies that are programed into the units... Channel Frequency 1 457.525 - This ch.used for IFB 10/18,19 2 457.550 3 457.575 4 457.600 5 467.750 6 467.775 7 467.800 8 467.825 - Car camera control data 9 467.850 10 467.875 11 467.900 12 467.925 - AVS tech communications 13 467.7375 14 467.7625 15 467.7875 16 467.8125 They also have radios programed in the 450 - 455 mHz Broadcast Remote Pick-up bands. At the racing I attended they used 455.350 as the P.L. communications to the pit camera. 450.350 was the input frequency to the repeater. Why they used the frequencies "backwards" from what the normal repeater frequency scheme would be isn't known. The car camera control data uses a 10-watt base station that transmits control tones to the cameras in the cars. You will hear a continuous carrier with DTMF (Touch- Tone) audio tones as the commands are sent. The microwaved pictures and sound from the in-car cameras are beamed up to a helicopter that has a microwave receiver on board, and then re-transmitted back down to the TV production truck on another microwave frequency. The TV truck used 123.050 to talk with the helicopter. The wireless mics that the roving announcers may use are Sony UHF mics in the 950 mHz band. Here is the channel allocations for the USA. Channel Frequency 11 947.250 12 948.250 13 950.250 14 951.750 15 949.000 21 947.750 22 949.750 23 950.750 24 951.250 25 948.500 31 949.250 32 948.750 33 950.000 34 951.500 Also, for you race fans who may end up at some SCCA racing events, here are some assorted track frequencies in use at the Texas World Speedway, in College Station, Texas. 151.625 - SCCA Race Control Primary 151.685 - SCCA Secondary 151.715 - SCCA 464.500 - Texas World Speedway 464.550 - Texas World Speedway To sum up, check all of the above frequencies for activity next time you are at the races, or any other major sporting event where there might be some wireless cameras wandering around!