Total posts : 45366
[quote:e9aa3f9685=”YvesRoy”]1) Since the peak of the wavelength is 5/8 of wavelength, what do you think if i make many turns on pvc form with 400 feet long wire (that is, my antenna would be my coil only on pvc form at the frequency of 1600 kHz)?[/quote:e9aa3f9685]
It is true that a 5/8 electrical wavelength vertical radiator has the highest field strength in the horizontal plane, per watt of input power, of all non-sectionalized vertical radiators. But to do that, the entire radiating portion of the antenna must be an electrical 5/8-wave long — in your case, about 376 feet of vertical, linear radiator. A loading coil used with a much shorter linear radiator is not the electrical equivalent of that, even if the total length of coil wire+radiator is 5/8 wavelength. Radiation from the coil itself is virtually nothing. And of course, Part 15 AM rules do not allow using a linear radiator longer than 3 meters.
[quote:e9aa3f9685]2) Does the AM signal propagate more at the end of the AM band than the beginning of the AM band (1600 kHZ vs. 550 kHz) ?[/quote:e9aa3f9685]
Propagation loss along a given set of ground conditions is less for lower frequencies than for higher ones. But the radiation resistance of a Part 15 AM antenna rises as the frequency increases, which usually improves the radiation efficiency of the antenna system (other things equal). The net result tends to favor using the higher AM frequencies.
[quote:e9aa3f9685]3) How using the NEC apps? For example, i want to simulate results the 3-meter antenna on 1630 kHz and 1460 kHz.[/quote:e9aa3f9685]
Modeling a complete Part 15 AM antenna including the coil and a buried ground system requires NEC-4, which is an expensive commercial program not widely available. A simpler way is to use some of the free programs downloadable from the website shown below, to calculate radiation efficiencies for various Part 15 parameters input by the user.