While searching eBay for 102" whips, I noticed it also returned numerous results for "6" Risers", which aren't particularly cheap either ($30-$40), and I thought why would anyone pay that just to rise 6 additional inches of antenna??..
Although I already guessed the answer because I brought up a the same point from a different angle last month: https://www.part15.org/community/antennas/92-whip-at-big-savings-why-not/ - CB enthusiast are apparently more concerned about this than Part 15 AM hobbyist, but it's equally as important for part 15. But everyone seemed to disagree with my point, so here I present it again..
So I asked Google: Whats the point of a 6" riser for a 102"?
And the Google AI answered what I knew it would:
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- The total length is key: A CB antenna performs best when its total length is an electrical quarter-wavelength for the Citizens Band frequency range (26.965–27.405 MHz).
- The formula: For a CB radio's frequency, the ideal quarter-wavelength is approximately 108 inches.
- The parts: A 102" stainless steel whip combined with a 6" riser or spring brings the total length to the perfect 108" for maximum range and the lowest possible Standing Wave Ratio (SWR).
But we as part 15 AM broadcasters don't really require a 6" riser for our antenna to achieve that optimum quarter-wave length, because we have an adjustable ground lead to work with that can accomplish the same thing as the 6" riser does.
R Fry had suggested before that a 3 foot antenna with 5 foot of ground lead actually may produce more field strength than a ground mounted transmitter with a standard 8' whip. It has something to do with the radiation decreasing the higher up the antenna it goes (it tapers off as you near the tip and is strongest at the bottom).
So because of this, I surmise it doesn't make any difference if you use a 102" whip, or save some money and get a 92" whip, because to begin with both lengths are wrong, but it's easily corrected by simply lengthening your ground lead to compensate.
Do you still think this reasoning is flawed?