Antennas & Cables
Data-Linc configures and supplies cables and data communication equipment to support our product line and as a service to our customers. Proper antenna/coax selection and installation is important to insure optimum results for your application. Data-Linc is not a cable or antenna provider for general purchase. For your FastLinc 802.11b applications, see a separate comprehensive list of FastLinc Family compatible antenna and coaxial cable products. Please also see Installation Instructions for more information about our antennas and cable assemblies.
For custom orders, please consult factory.
The LMR-240 (smaller coax) has a smaller bend radius and will cause less strain on the SMA connector of the radio. Additionally, only the smaller coax can take an SMA connector directly. It is possible to put an “N” connector on the LMR-400 (larger coax) and then use an N-to-SMA adapter, but this is not recommended. This scenario allows for slightly lower losses but requires very deliberate strain relief for the coax-to-radio connection. The attachment to the radio should always be made with a minimum length of LMR-240 (unless the customer has a very specific reason not to do so).
US FCC regulations allow for a maximum Effective Rated Power (ERP) of 4W. Since the 900 MHz radio modules are capable of a maximum output of 1W, the entire transmission line including the antenna must have a total gain of no more than 6dB. 2.4 GHz systems must have a total transmission line and antenna gain of no more than 9dB. Data-Linc Group lists the specifications of its approved antennas in dBd, which means these figures may be plugged right in to the formula which follows. The total transmission line gain can be calculated simply by adding the gain of the antenna (dBd) and the losses of the feeder cable (coax), connection points (pairs of coax connectors) and surge protector (if used).
Coax LMR-240 has losses of 7.6dB/100’ at 900 MHz, and 12.9dB/100’ at 2.4GHz. Coax LMR-400 has losses of 3.9dB/100’ at 900 MHz, and 6.8dB/100’ at 2.4GHz. Please note that LMR-400 has nearly half the losses of LMR-240 in both frequency bands. At distances over about 25’ power losses can be reduced by using a 3’ stub of LMR-240 with an “N” connector on the antenna end, in combination with the desired length ofLMR-240. The savings in power dissipation make it worth the small losses in the additional connector pair.
The total transmission line gain then equals G – L – .48(C) where “G” is the gain of the antenna in dBd. “L” is the total loss in the coax itself, found by multiplying the appropriate specification listed above by the number of feet of coax. And, C is the number of coax connector pairs (or connection points) in the entire transmission line.
The maximum allowable transmission line gain is 6dB for 900MHz units, and 9dB for 2.4GHz units, assuming the radios are set for maximum transmit power. Data-Linc Group does not authorize the sale of systems capable of exceeding these specifications to any customer.
Several transmission line configurations are shown in the accompanying drawings. Users are not limited to these configurations. The drawings merely represent the configurations most likely to satisfy customer requirements. The new coax cable selections are intended to allow the end user greater flexibility while reducing the need to stock many different cables. All coax cables used in the past will still be available under their old model numbers. (See also Antenna Installation Instructions.)