Overview

MFJ 2910 160 and 80 Meter Matching Networks

MFJ-2910 160 and 80 Meter Matching Networks are remote relay-switched tuning coil assemblies designed specifically for any 43 ft. vertical. Band ranges are switched in the shack with the included bias tee on the feedline. These networks improve tuning and efficiency on 160 and 80 meters and include the 4:1 balun to maintains 60-10 meter full band coverage with a user supplied wide range tuner in the shack. With these matching networks, extra coaxial cable length and extra losses are reduced, while the user's in-shack tuner expands the 160 and 80 meter band coverage. On the Amateur bands from 160 to 10 meters, MFJ-2910 Matching Networks are designed to handle up to 750 watts CW safely. DX Engineering recommends reducing power for RTTY and other high duty-cycle modes.

Here is how the MFJ-2910 works:

- With no power applied the MFJ-2910 operates on 160 meters by default. With the included bias-tee model MFJ-4118 switch in the middle "OFF" position, all relays are off, which bypasses the 4:1 balun and connects the 160 meter series coil and shunt tuning coil taps. On the 43 ft. vertical, very high voltages are produced on a 160 meter base loading coil. A unique isolation scheme in this unit arranges all of the de-energized relays to prevent arcing on this band.

- Operation on 80 meters is selected by switching the Bias-Tee to DC-, which applies a negative voltage to the MFJ-2910 relays, switching coil connections to the 80 meter taps while keeping the 4:1 balun disconnected.

- Operation on 60 through 10 meters is selected by switching the Bias-Tee to DC+, which applies a positive voltage to the MFJ-2910, switching the relays to connect the internal 4:1 balun in line with the antenna and bypassing the 160 and 80 meter coils.

For each band range selection, using low power, tune up your 43 ft. vertical antenna and MFJ-2910 Matching Network using your wide range tuner according to the instructions supplied with the tuner. Once the tuner is adjusted for low SWR, then you can operate at a power level that corresponds to the capabilities of your tuner.


IMPORTANT NOTES:

- MFJ-2910 Matching Networks include the Dual-Polarity Bias-Tee model MFJ-4118 which must be powered with an isolated 12-15 Vdc only! Use an optional wall transformer such as DXE-PSW-12D1A or MFJ-1316. A shack DC power supply that has a negative chassis ground that is common to the coaxial cable CANNOT be used.

- Use only "DC Pass" lightning surge protectors in the coaxial cable for this antenna matching system. DO NOT use any "DC Block" protectors on the feedline because they do not allow the positive and negative voltages of this relay control system.


Add an MFJ-2910 160 and 80 Meter High Efficiency Matching Network to your 43 foot vertical antenna to bring the antenna impedance within the range of your wide range antenna tuner for efficient all band operations, 160 through 10 meters!

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