Let's Pick The Nits on the % Wave Claim on some Verticals

[Wire Weasel]

Mildly amusing to consider how some manufacturers want to stretch the math regarding Wavelength Claims on particular-length antennas. I know of two at least that come in at 19 feet long and they are wanting to call them 5/8 types but they would seem to be closer to 1/2 wave. I realize that 5/8 sounds like a better sell than 1/2. The great majority of 5/8 Advertised Verticals are 22.5 - towards 23 feet long .... which matches the math, and likewise the bulk of 1/2 wave advertised antennas are 17.5~18.5 feet in length .... again matching the math.
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I guess 5/8 wave IS sexier than 1/2 wave

 

[sp5it]

So called mobile 5/8 are shortened whip extended electrically to 3/4 wave (3rd resonance). Wrongly named 5/8.
Another type is 1/4 shortened whip extended electrically to 1/4 (first resonance)

There is no such a thing 5/8 mobile.

 

[brandon7861]

Wouldn't it be nice if all antenna manufacturers listed the physical wavelength of the radiator AND complex imedance of that element before they went and matched it to 50Ω? Who cares what their coil extends it to, I want to know how much meat is on the bone!

I don't think it is accurate to associate resonance with any n/4λ. Resonance is merely the absense of reactance. We can do that with any length wire, so when the matching network accounts for cancelling a notable amount of reactance, referring to electrical wavelength becomes uselessly deceptive.

 

[The DB]

So called mobile 5/8 are shortened whip extended electrically to 3/4 wave (3rd resonance).

They are electrically 1/4 wavelength. The entire antenna is essentially a loading coil, which lengthens the 4, 5, or whatever foot length the antenna is to 1/4 wavelength. They only get off calling it 5/8 because they design it to use a physical 5/8 length of wire. If these antennas were electrically 3/4 wavelength, part of the radiation that was at a lower angle would be aimed up at the sky. Such things happen when the antenna is electrically longer than 5/8 wavelengths long.

There is no such a thing 5/8 mobile.

In the world of CB this is true. In the world of VHF ham radio...

Resonance is merely the absense of reactance.

This is absolutely true. The modern view most people in the hobby have was (I believe) brought into acceptance by the widespread use of coax, to the point of monopolization over all other feed line types. (I think) the general knowledge of today is being limited to experience with said medium, and the effects of its limitations, which many people don't even realize exists.

Most people in the hobby these days only see resonance when they have X=0 at the antenna's feed point, but the reality is, when it comes to resonance, this is actually only a special case.


The DB