If there is ⅝ Wave length of wire, which is in most mobile antennas, then it is electrically a ⅝ wave and for info the best wave length to work off it is ½ wave because no ground plane is needed.
The length of wire inside of the coil does not correlate with the effective operating wavelength of the antenna. What matters is that the coil needs to be of a certain amount of inductance to establish resonance with a less-than-1/4λ whip (which is capacitive by nature). A coil of 'x' inductance with closely-spaced turns of wire will require less length of wire than one that has wider-spaced windings. Fact remains, the antenna as a whole operates principally as 1/4 wave.
http://en.wikipedia.org/wiki/Whip_antenna#Electrically_short_whips
Yes but it starts at the bottom, if that is blocked by metal it screws up the radiating pattern.
RF current is greatest, and voltage lowest at the bottom. As the energy travels along the whip, the current becomes less, and the voltage becomes greater. Because the voltage is greatest at the tip, any proximity of an object at the tip will affect the antenna much more than something in proximity to the antenna's base.
The antenna's entire length does radiate, however it's radiation energy is much greater at the tip than at the base.
¼ wave length is 9 feet which is 108” not the 102' of the steel rod. The spring is 6” and makes up the difference to the ¼ length. If you tried to match it without a spring you would be way off.
No, 1/4 wave at 27.185 MHz (ch 19) is ~103¼ inches.
234 ÷ 27.185(MHz) = 8.607688(feet) × 12 = 103.292 inches
An online calculator for 1/4λ antennas is
here if you don't believe me...
No doubt, a spring does change it's resonant freq, however IME it only affects the SWR by maybe .3 or so (changes a 1.0:1 to 1.3:1 or vice-versa), and you can always trim the whip shorter too.
I would be very surprised if you had a 1 to 1 match across the full band. No antenna I know of has that characteristic. You should tune for lowest SWR on the channel or frequency you use the most.
A full wave length antenna would be 36 feet long, if correct in length, coax, connectors and power output of the radio then you will get a perfect match but not today, I don’t think it even exists.
I said 1.1:1 (that's: one-point-one-to-one), not 1-to-1.
It seems you do have an aversion to full-length CB antennas, so it makes sense you haven't experienced one in a proper installation yet.
Bandwidth between the 1.5:1 SWR points on a 1/4λ whip is on the order of about 1.5 MHz, which would be equivalent to having a whole additional set of 40 channels both above and below the regular 40 channels.
With your 1:1 SWR set on CH 19, a 1.1:1 on CHs 1 & 40 is very possible.
(and please note that I said "
full-length" not 'full-wave'. Full-length refers to a full 1/4-wave whip as opposed to a coil-loaded (shortened) antenna. It has nothing to do with the actual length of the free-space RF signal. A full-wave vertical antenna would not radiate in a useful manner anyway (exhibits a "cloverleaf" radiating pattern, which has nulls instead of lobes in a horizontal direction, precisely where you would want the signal to go/be received from).
If it is a perfect antenna which does not exist, then you could be correct but it will depend on the mounting point. 60 feet in the air with nothing around it yes you would be correct but mounted on a vehicle no there are too many variables.
Not sure what in that is relevant here... No doubt, a "perfect" antenna does only exist on paper (or I guess maybe in bytes too). A ground-plane antenna (what a 1/4λ whip on a vehicle roof is) does not reference actual earth ground, so is not affected by it's height above it.
It is hard to beat a ½ wave fiberglass whip made by a good company like Wilson, their antennas have the highest “Q” value of any on the market. The “Q” Value is an efficiency rating applied to antennas.
Now the biggest problem now-a-days is most antenna companies are going to ⅝ wave ratings, why, maybe because people think the higher the wave rating the better the antenna but again it isn’t.
I think you're getting a bit caught up in the marketing claims of CB antennas (the same ones I mentioned that have no regulations and few guidelines to govern them).
"Q" simply describes a ratio of power stored in a set of reactive components (the antenna whip's capacitance and it's loading coil as an example) vs the amount of power lost or dissipated by their resistance (and relates to operating bandwidth of the circuit). It is not something applicable specifically to antennas.
http://en.wikipedia.org/wiki/Q_factor
Ideally you do not want to "store" any of your RF energy in a loading coil
at all, you want the antenna to radiate as much of that energy into space as possible.
And yes, Wilson does make great antennas, however they too are among the perpetrators of some of the marketing hype.
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