Questions tagged [resonance]

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2 votes
4 answers
163 views

Wave bounce inside a resonant antenna

Let's assume we have a transmitter, a feed line, and a standing wave antenna (dipole, etc.). The transmitter is matched with the feed line, and the feed line is matched with the antenna, which is why ...
elgroovy's user avatar
4 votes
1 answer
146 views

Chimney Flashing Affect on Dipole Antenna Resonance

I put up a 40m dipole off a metal mast attached to a chimney mount on a 25' roofline. The chimney has metal flashing on the top with a metal spark arrest dome on top. I have 125' of RG8X feeding an ...
K5KUE - Conrad's user avatar
2 votes
5 answers
308 views

Minimal SWR at resonance

Why does a minimal SWR NOT indicate antenna resonance? Would SWR 1:1 be required to indicate antenna resonance?
Jan Hus's user avatar
  • 167
2 votes
1 answer
290 views

Resonant RF transformer using a piece of wire (no capacitors)

I previously posted this in electronics StackExchange here, but I believe Ham is more proper place for it as it closely relates to antennas. I'm curious if it is possible to build a spark-gap Tesla ...
elgroovy's user avatar
5 votes
6 answers
2k views

Does an antenna pick up signals of all frequencies or only its resonant frequency?

I heard that an antenna picks up signals of all frequencies, and then these signals are filtered by a circuit using an inductor and capacitor, and that this is how a radio is tuned. However, I also ...
Urthona26's user avatar
  • 151
5 votes
5 answers
332 views

Antenna tuner at the transceiver output confusion

I am a bit confused. Let's take a HF transceiver for example. My understanding is that the output impedance of the transmitter is 50 ohms. The impedance of the coaxial cable feedline is 50 ohms, and ...
Engineer999's user avatar
-1 votes
2 answers
107 views

Broadband dipole with no standing waves?

If a diode or directional coupler is fitted at the outer ends of the elements of a dipole, would this stop current reflected from the ends and so result in no standing wave on the antenna ? It can't ...
Andrew's user avatar
  • 3,665
0 votes
1 answer
88 views

Does antenna Q cause distortion?

Everyone knows that a 1/2 λ dipole has on the elements a standing wave the voltage and current of which are a bit less than 90° out of phase with each other, and the departure of this phase difference ...
Andrew's user avatar
  • 3,665
2 votes
3 answers
481 views

Why do ham radio operators say that a full wave dipole isn't resonant?

Every reputable antenna book that I've read says that dipole antennas are resonant at integer multiples of a half wave length. Wikipedia describes resonance as: the phenomenon of increased amplitude ...
Andrew's user avatar
  • 3,665
0 votes
2 answers
115 views

Is the phase difference between the voltage and current of the standing wave on a dipole antenna constant along the dipole's length?

Everyone knows that a 1/2 λ dipole antenna has on it a standing wave of RF energy the voltage and current of which are about 90° out of phase with each other. The standing wave is circulating reactive ...
Andrew's user avatar
  • 3,665
1 vote
2 answers
205 views

Does the self inductance and velocity factor of the elements of a dipole antenna change its resonant frequency?

Below are well known equations from Wikipedia for the resistance and reactance in the impedance of a dipole antenna. where $a$ is the radius of the conductors, $k$ is the wave number 2πf/c, $η_0$ ...
Andrew's user avatar
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