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Balun Designs now offers an excellent reduced power version of our popular model 49131.  Built with the same craftsmanship as all our other units, this new model will allow you to either replace your current matching unit or construct a new medium power end fed half wave antenna. We also install an additional stud which can be used for a separate counterpoise wire rather than forcing the use of the feedline's coax shield.  This is the perfect unit for your 100 watt transceiver and will allow you to run FT8 all day. Attaching a counterpoise wire to the common point of the auto-transformer provides the antenna radiator something to push against rather than the coax shield. The counterpoise wire does not have to be similar in length to the main radiator and the antenna works best with counterpoise length of 0.05 λ on the lowest band the antenna is cut for.  This calculates to ≈ 12.5 feet for an 80m end-fed. This transformer is designed to be used with an end fed half wavelength of wire only.  The length should be calculated based on the lowest frequency to be utilized.  So for example 80m could range in length from 120 to 133 feet.  Use with other random lengths can potentially damage the transformer depending on power level in use.    Caution: When used at full power rating of 500w, the antenna must have a low SWR on the band selected and be used on a 50% duty cycle.  Any SWR measurement taken with the transformer at the feedpoint should not exceed 1.5:1 with NO tuner in use.  There are numerous configurations available online that will accomplish this on multiple bands (Google search "end fed half wave antennas").  If the transformer is used with an external tuner in conjunction with a single wire antenna typically 130-135 feet in length, power should be reduced on those bands that show an SWR above 1.6 to 2:5 without the tuner. 

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