Use of passive repeaters for tunnel surface communications
Many times there is a need to establish ratio communication between the surface and a beam enclosure. When one solicits communication companies for solutions, the answer is often to purchase expensive communication equipment such as repeaters or radiax type cable which can cost in the tens of thousands of dollars. This TM will describe an inexpensive solution to this problem and the results that can be expected. The cost of a passive repeater is $100--$200 depending on how elaborate one wants to be. A passive repeater system consists of two antennas connected together with a transmission line. When using VHF or UHF transceivers, one can use 5/8 wave mobile antennas, such as the Larson NMO406-CK for the 400--420 MHz range, with the antenna connected to a 19 inch square piece of aluminum to act as a ground plane. This type of antenna has reasonably good gain, seems to be adequate, and is inexpensive. Another antenna choice is to cut a dipole out of bus wire and solder this wire to a female N connector. Using a dipole seems to work OK in the tunnel and avoids the problem of having a wire sticking down for people to poke their eye with. The cable connecting the antennas should be of good quality so that the signal lost in the cable is minimal. The authors chose Belden 9913 coax. This cable has a characteristic impedance of 50 ohms and has 2.7 dB/100 ft. of attenuation at 400 MHz.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC02-76CH03000
- OSTI ID:
- 226068
- Report Number(s):
- FNAL-TM-1966; ON: DE96009371; TRN: AHC29610%%110
- Resource Relation:
- Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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