I am interested in the mf solutions vlf transceiver to get on vlf. This transmitter has a output of 25 watts. For an antenna on this frequency I plan on using a 230 foot long magnetic loop element. According to the 66 pacific mag loop calculator this will yield a transmit efficiency of 17%, so, my eirp should be 4.25 watts. Is this approach to fulfilling the law on maximum eirp good enough? I really do not want to radiate more power than allowed by law. My mag loop element is composed of a strip of aluminum flashing 2 inches wide. Each 50 foot long strip of flashing is pop riveted (20 ea) to the next piece of aluminum. Then the head and base of each rivet is aluminum soldered so that a low resistance join can be made. A vac variable cap is bolted across the ends of the strip for tuning. My experiments with flashing strip loops has found that feed loops do not work well, and yield swr's around 2 and higher. The first time I tried a gamma match I achieved a 1.2 to 1 match. The gamma element was simply a wire extending from the center of the loop where the coax was grounded to the loop, down one side of the loop 20% of loop length. The wire was coiled around the loop about 3 times to prevent the wire swaying in the wind which causes wild swr swings. For my portable 160 meter loop, I erect the loop in a delta loop shape with the cap at the bottom center, The gamma feed ground is at the top, while the gamma feed tap point is 20% of the loop length down the side. A 28 foot high fiberglass mast and ground stakes allows me to put up my 160 meter portable loop in less than a hour.
Best Regards
Jim