Questions tagged [waves]

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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
73 views

How to calculate phase constant for a coaxial cable?

inner and outer conductor diameters of 1 mm and 5 mm respectively, is filled with a non-magnetic PTFE dielectric having εr = 2.55. frequency = 1 GHz.
• 21
1 vote
187 views

Waveguide size for 2.4 GHz

I'm thinking to make a wave guide that has diameter 1/8 of the wave length. At 2400mhz the full wave length is about 125mm. I have aluminum pipe that is 16mm. So 8*16 = 128mm (very close to 125mm). If ...
133 views

Is a 1/2-wave coax cable shorter or longer than the full-speed 1/2-wavelength?

If I want to cut a half wavelength segment of coax for the two-meter band and the velocity factor is 85%, is my cable going to be shorter or longer than a meter? I'm trying to figure out if the ...
• 723
130 views

Why can a monopole antenna receive wavelengths significantly longer than its physical length?

I am new to ham radio and have been playing with a RTL-SDR receiver to which I have connected a vertical 1.5m monopole antenna. However, I can receive transmissions belonging to the 40m band (albeit ...
1 vote
461 views

Would it be possible to light up a bulb wired one side to a transmitting antenna?

Would a light bulb light up if wired to the end on an antenna ? If you would connect a light bulb on one of its poles to a quarter wave antenna like in the schematics below, would the bulb light up ...
• 113
1 vote
127 views

Wavepropagation through air - EMC test values 100V/m

I am reading the Automotive International standards ISO 11452 and it states that I must have a chamber in which I must generate 100V/m on a range of frequency. My question is: In which circumstances ...
• 11
1 vote
249 views

How can an RF coil emit at 3 different frequencies at the same time during Amplitude Modulation?

This image shows how an AM wave is generated and emitted: This comment explains how 3 separate waves are sent at once to represent an AM wave: the transmitter does not transmit one pure sine wave at ...
• 311
665 views

Why does a sine wave show two peaks in the frequency domain on GNUradio?

I constructed the flow graph in GNUradio 3.7 as below: I know a sine wave has only one frequency, so what causes the frequency sink to show two peaks?
• 600
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 ...
• 3,665
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 ...
• 3,665
482 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 ...
• 3,665
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 ...
• 3,665
1 vote
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, $η_0$ ...