Insertion Loss Data for MN8CX Cores

Since the publication of the Second Edition, experimental research has yielded significant improvements in the efficiency of r-f transformers used in Beverage antenna construction. The MN-60 and BBR-7731 materials have been replaced by higher efficiency MN8CX material. The insertion loss of r-f transformers using MN8CX material is shown in the table below. It is clear from the table that additional efficiency may be obtained by stacking two cores in each transformer. The procedure is simple. Just place one core on top of another and wind the transformer using the turns information in the antenna diagrams. Note, however that at 10 mHz the single core transformer is more efficient. Double coring improves efficiency at all other listed frequencies. For use in the 160-190 kHz experimental VLF band I recommend using 3 cores per transformer. Cores can be cemented together with epoxy to make handling easier when winding.

TRANSFORMER INSERTION LOSS dB

Frequency - mHz Single MN8CX Core Double MN8CX Core 0.1 0.5 1.0 1.8 2.0 3.5 3.9 7.2 10.0 - 8.01 dB - 1.03 dB - 0.57 dB - 0.51 dB - 0.49 dB - 0.32 dB - 0.27 dB - 0.40 dB - 1.29 dB - 3.70 dB - 0.38 dB - 0.24 dB - 0.21 dB - 0.18 dB - 0.07 dB - 0.03 dB - 0.32 dB - 1.42 dB Above results apply only to cores dimensioned: OD = .5 in, ID = .312 in, T = .25 in. Back