Figure 4. KCST-AM Kinstar antenna drive impedance measured at the output J-plug of the antenna matching network by Bob McClanathan, PE.
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Another advantage of the antenna is the wide audio bandwidth it offers in comparison to the typically narrow band characteristics of electrically short AM antennas. Figure 4 illustrates the small change in resistance and reactance of the KCST Kinstar measured over the 1250 ±15kHz band.

The inherent audio bandwidth performance of the Kinstar is evidenced by the less than 2 ohm variation in R and the less than 10 ohm variation in X over the 30kHz bandwidth of a typical HD Radio channel. Following the initial antenna tune-up and commissioning of the transmitter operation into the antenna Bob McClanathan responded, "This past Sunday, Jan. 11, I worked with Jon Thompson and Sparks Scott at KCST in Florence, OR, to complete the ATU adjustments and measurements for their new Kinstar AM antenna. I am very impressed with the quality of the antenna construction, and the operation is much better than what I expected. The impedance at 1250kHz is Z=15.1 + j80.0 ohms and is flatter than a pancake ±20kHz. Would be excellent for IBOC but fortunately KCST is not going there.

"The Kintronic ATU is of excellent quality as usual and built for easy impedance measurements. Very little adjustment was necessary to set the T for Z=50 ± j0 at the transmission line input. The KCST Kinstar is excellent in performance. I met a neighbor near the antenna site who is very pleased with the unobtrusive and nearly invisible appearance of this antenna. When considering the FAA restrictions, local zoning and neighborhood objections, this Kinstar will certainly prove valuable and popular for non-directional AM antenna sites."

King is president of Kintronic Labs.