I read in a book the following: An Electrically short antenna means that is shorter than one half wavelength which also means that is not resistive. I have 2 Qs.
1.When it says "shorter than one half wavelength" it means the physical length? 2.Why being electrically short means it is not resistive?1) The physical length is shorter than one half the wavelength of the signal 2) An antenna or transmission line which is not terminated with its characteristic impedance will have an input impedance which has phase angle and will be an impedance rather than a pure resistance.
fred.
A short antenna looks like a capacitor.
John
On 17 Jan 2006 09:05:45 -0800 in sci.electronics.basics, "thejim" wrote,
Mainly, but if it says electrically short then I think it means having the electrical characteristics normally associated with an antenna physically shorter than the resonant length. Something other than physical length that affects resonance could be figured in.
If the antenna is a resonant length for the frequency in question, then its inductance reactance and capacitance reactance cancel out leaving only the resistive components as seen by the transmitter. The current neither leads nor lags the voltage at the feed point.
If shorter, it is capacitive + resistive, current leads voltage. If longer, inductive + resistive, current lags voltage. Or is that the other way around?
I have concuded somewhere regarding Electricaly short antenna. I just want to mention it to see if my conclusions are correct. If the antenna is shorter than 0.25 of the wavelength then there will be a phase angle as a result of disturbances and that is why there is impendance rather just resistance Am i saying it correctly?
Check some of these resources:
There's a whole nother side to google, you see.
Good Luck! Rich
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