Questions tagged [resonance]
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12 questions
0 votes
2 answers
59 views
120 in vertical longer but flat SWR on 27.185 MHz
I recently put a antenna bracket adapter onto a 4 ft piece of steel pipe attached to a tree (6 ft high) with a ratchet strap. One radial, about 10 ft long, is going at a downwards angle to a metal ...
- 31
2 votes
4 answers
226 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 ...
- 47
4 votes
1 answer
340 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 ...
2 votes
5 answers
689 views
Minimal SWR at resonance
Why does a minimal SWR NOT indicate antenna resonance? Would SWR 1:1 be required to indicate antenna resonance?
- 167
2 votes
1 answer
388 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 ...
- 47
4 votes
6 answers
4k 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 ...
- 141
5 votes
5 answers
584 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 ...
- 568
-1 votes
2 answers
138 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 ...
- 3,817
0 votes
1 answer
125 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 ...
- 3,817
2 votes
3 answers
1k 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 ...
- 3,817
0 votes
2 answers
345 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 ...
- 3,817
1 vote
2 answers
286 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, $η_0$ ...
- 3,817