Total posts : 45366
A casual reading of Rich’s post might cause some of the audience to think that he and I disagree about our numbers. Actually, we are in complete agreement. Rich is illustrating how difficult it is to get good efficiency from a 3 meter whip at ground level, and even from a 3 meter whip elevated 6 meters. The radiated power that corresponds to the field strength reported by the FCC is 469 mW from an electrically short antenna, as I stated in my previous post. Rich reports that, to get this much radiated power at 1620 kHz, it is necessary to apply about 80 watts to a 3-meter antenna with 20 ohms of loss resistance, and about 4 watts when the antenna is elevated 6 meters. This implies an increase in efficiency by a factor of about 20 for the elevated antenna.
In my post, I mentioned only the radiated power, and not the power that has to be applied to the antenna to get the radiated power. Rich also says that about a half watt applied to a lossless 1/4 wave monopole produces the field strength the FCC measured. This is true, because a lossless electrically short antenna has only slightly less gain than a lossless 1/4 wave monopole (469 mW is about a half watt).
As I said, there is no disagreement. I just wanted to clarify the two posts.