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# Tag Info

## Hot answers tagged resonance

7 votes
Accepted

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

Let's consider a simpler case by bringing the tips of a half-wave resonant dipole together so the two wires of the dipole are parallel, making a quarter-wave section of of balanced transmission line. ...
• 51.8k
6 votes
Accepted

### Does antenna Q cause distortion?

As far as I can see, no. The shape of the standing wave might have an effect on the antenna's spatial pattern, but the fact that it is a standing wave pretty well implies that it's steady-state, ...
• 12.4k
5 votes

### Antenna tuner at the transceiver output confusion

Having a transmatch (antenna tuner) at the feed point of the antenna can be an excellent way to solve the problem of a mismatched antenna; an antenna system with the transmatch at the feed point of ...
• 9,222
5 votes

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

All frequencies. But, there's a big difference between "picking up" a signal, and how well an antenna will "pick up" a signal. Any metal object will pick up almost any RF signal at ...
• 13.3k
4 votes

### Minimal SWR at resonance

Why does minimal SWR DOES NOT indicate antenna resonance? Well, because they're not the same thing. Would SWR 1:1 be required to indicate antenna resonance? No. A zero reactance indicates resonance....
• 12.4k
4 votes

### Wave bounce inside a resonant antenna

Now our antenna creates a standing wave. Nope, not a wave in the "propagating wave" sense. That's the fallacy here: there's not a wave propagating forth and back. What is standing is indeed ...
3 votes
Accepted

### Wave bounce inside a resonant antenna

Keep in mind that when you are talking about standing waves, you are talking about voltage. Also, a systems' feedline is containing the EM energy, and the antenna is shedding that energy. With regard ...
• 930
3 votes

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

Notice how there are no terms anywhere in the equations for anything related to the self inductance of the elements or related to the fact that radio waves travel slower in metal than in air. Indeed, ...
• 51.8k
3 votes
Accepted

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

Here's a schematic of a spark-gap Tesla coil from the Wikipedia article: L1 and L2 are coupled together by their magnetic fields, and so act as a transformer. Such a Tesla coil depends upon ...
• 9,222
3 votes

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

It depends on the antenna. Some antennas are very broad band and do more or less pick up every frequency, but may have more sensitivity on some than others. Typically, it would pick up more on its ...
• 6,320
2 votes

### Antenna tuner at the transceiver output confusion

It's important to remember that a feedline having a 50-ohm characteristic impedance doesn't "force" any signal appearing at its terminal to be 50 ohms; it just means that if you give it a ...
• 12.4k
2 votes

### Wave bounce inside a resonant antenna

Don't forget: The antenna is a 2 port device: power transferred from the transmission line to the antenna (#1), and power further transferred from the antenna to free-space (#2). The power ...
• 4,105
2 votes

### Chimney Flashing Affect on Dipole Antenna Resonance

I think everything is working about as you would expect. The impedance of antennas is very sensitive to their height above ground, and at 40 m you are always less than a wavelength away where the ...
• 11.2k
2 votes

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

I think your question is basically : "Does an antenna receive signals at all frequencies?". The answer is in the antenna's S11. The S11 is a measurements were you send a wave to an antenna ...
1 vote

### Wave bounce inside a resonant antenna

Consider a single finite length wire, bent in an L shape, 1/4 wavelength of some given frequency F0 from the end. A current impulse, say driven by a single spark from a spark transmitter, will indeed ...
• 13.3k
1 vote

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

Your question is similar to others that have been asked here before. Here are a few: Does a resonant antenna work better than a non-resonant antenna? What exactly makes an antenna resonant? What is ...
• 9,222
1 vote

### Antenna tuner at the transceiver output confusion

In the special case where transmitter output impedance, transmission line characteristic impedance, and antenna impedance are all the same, for example 50 +j0 ohms, then everywhere on the transmission ...
• 3,685
1 vote

### Antenna tuner at the transceiver output confusion

The output of the transmitter will always be 50 Ohms, it's what the transmitter sees that's important. If the transmatch is in the shack and tuned properly, the transmitter will see 50 Ohms. When ...
• 193
1 vote

### Antenna tuner at the transceiver output confusion

Lets simplify the scenario a little by using a resistor at the end of a 50 foot long 50 Ohm impedance feedline instead of an antenna. If the resistor is zero Ohms, then about 100 nS after enabling a ...
• 13.3k
1 vote
Accepted

### Broadband dipole with no standing waves?

Any change in impedance at the end of a wire, different from the rest of a transmission-line-like wire, will reflect some current. An impedance matched resistor at the ends of a dipole won't reflect a ...
• 13.3k
1 vote

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

I hope it's not bad form to reply at this late date, but there are a few issues I did not see directly addressed. First, any radiator of a capacitive type antenna (not just a dipole) is resonant at ...
• 361
1 vote

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

@Andrew, I wonder if you are interpreting this type of drawing: as a depiction of current and voltage being out of phase. To be clear, it is not; this image depicts the relative current and voltage ...
• 361
1 vote

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

The total current (according to physics) across any region around the antenna is the sum of the conduction current within the elements plus (according to Maxwell's equation) the displacement current ...
• 13.3k
1 vote

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

Note the velocity factor of the metal also doesn't appear in generic equations for inductors. The inductance is more about the permeability of the free space surrounding the conductive elements, not ...
• 13.3k

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