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"Top Hats" for Part 15 AM Radiators

R

rfry

Various website posts from time to time have proposed attaching several short, horizontal wires to the top of a 3-meter "Part 15 AM" monopole so as to improve the performance of the antenna system -- with some intuitive thoughts about how that improvement is achieved.

The NEC analysis at the link below gives some engineering-based insight into this.

Just to note that the position of the FCC on this subject with respect to compliance with Part 15.219(b) is unknown.

http://i62.photobucket.com/albums/h85/rfry-100/TopHat.gif
 
Good Info Rich. In the case of the Rangemaster, using a standard CB whip attaching spokes would prove impractical. However, purchasing a mast from Hustler for use in amateur radio applications might work as companies like DX Engineering manufacture devices that attach enabling such a configuration.
 
Re: "Top Hats" for Part 15 AM Radiators (Expanded)

A variation of this is a configuration of a 3-m monopole with no top hat, but with 4 x 6-ft horizontal radials attached together with the base of the monopole -- where all conductors are elevated 9" above the earth, and none has direct contact with the earth.

This configuration makes it possible to use NEC-2 to calculate groundwave field intensity vs. distance over a real earth path. The results of such a NEC study are shown in the graphic linked below.

Once again, the position of the FCC on this subject with respect to compliance with Part 15.219(b) is unknown.

http://i62.photobucket.com/albums/h85/rfry-100/Monopole_with_Base_Radials.gif

RF
 
Now if I understand your graphical representaion, using a quality receiver with a properly matched receiving antenna, I could expect a S-Meter reading of S9 or close assuming S9 = 50 uV?
 
druidhillsradio said:
... using a quality receiver with a properly matched receiving antenna, I could expect a S-Meter reading of S9 or close assuming S9 = 50 uV?
Click to expand...

S-meters give a relative measure of the conducted voltage present at the antenna input terminals of the receiver, and not the arriving field intensity. The voltage at the receiver input will depend on the characteristics of the receive antenna, and more.
 
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