MFJ-915 RF Isolator 1500W



MFJ-915: The MFJ-915 RF Isolator is a 1:1 Current Balun designed to be placed in line with a 50-Ohm coax. The RF Isolator is effective from 1.8 to 30 MHz. It was designed to improve the performance of all amateur stations, fixed or mobile. MFJ-915 will reduce or eliminate stray RF often found on coax. This stray RF can cause burns and other problems with electronic equipment in ham-shacks and vehicles. Stray RF also results in a loss of radiated power from the antenna, which will lead to a great reduction in signal strength. Use of the MFJ-915 will increase the efficiency of all amateur stations. Its made up of 50 Ferrite Core Beads, placed onto a 13-inch piece of RG-303 coax. The coax and SO-239 connectors have Teflon(R) for maximum insulation and extended life of the product. The RF Isolator is enclosed in schedule 40 PVC pipe for maximum strength and protection.

Theory of operation:
The RF Isolator can reduce the amount of RF radiating from coax feeding an antenna. Stray RF
can result in a loss of radiated power from the antenna, which will lead to a reduction in signal
strength. This loss of power is critical when using a short or otherwise inefficient antenna, and/or
using very low power.

The RF Isolator should be placed close to the transmitter, in line with the coax feeding an antenna. This can be done using a coax patch cable such as the MFJ-5803 or MFJ-5806.
Install the RF Isolator by connecting the coax cable from your antenna to one end of the Isolator.
Connect the other end of the isolator to the transmitter using a short length of coax.
Check to see that the connections are secure.
Check the SWR of the antenna using a very small amount of power (less than 10 watts) and an SWR meter. An SWR analyzer such as the MFJ-269 also may be used.