Why have a shortwave radio?

Answer 1

Like a glass that resonates with soundTo understand how a radio receives signals, it helps to compare it to how a glass shatters when a singer hits a specific note: When the vibrations in the air match that particular frequency that the glass is tuned to, the glass resonates and absorbs the energy (and shatters if it absorbs too much). So, the glass is a kind of detector or receiver of a particular frequency of sound, and ignores all the other frequencies.

A radio basically works the same way, except instead of sound vibrations, it is tuned to pick up electromagnetic vibrations. It is tuned to a particular frequency, and picks up the signals with that frequency, just like how the glass picks up the signal from a specific frequency of sound in the air.

Basic principle behind every radio is the process of modulation (superimposition of signals on carrier waves collectively called baseband signal) and demodulation of radio waves.

Answer 2

Shortwave radio works like an AM broadcast band radio, but has different circuit called HF tunable circuity to respond to the whip antenna or coil antenna inside the radio, the coil antenna however responds to the SW 1 nighttime bands, as long there is a wire antenna connected to the terminals. SW2 is still responsive with the coil without the ferrite, but still needs an wire antenna for better response. Newer shortwave radios use internal circuitry instead of coils to receive the different frequency ranges using the RF tunable circuitry and L/C tunable circuit to receive 3 MHz to 7 MHz SW and SW2 7 MHz to 26 MHz. Most communications receivers use the same way but has better design to handle very strong signals and get rid of images and are analog and digitally tunable HF circuits. WFM shortwave radio is possible, but it will take up bandwidth so Narrow FM is used for 10 meter reception. PLL circuits respond to the L/C tuned circuits to pick up from 1711 kHz to 30 MHz and below 1711 down to 150 kHz.

The LW bands use the a different ferrite coil but with a higher inductance around 250 to 300 turns and the circuitry tunes lower than 530 kHz from 520 kHz to 150 kHz Some radios use a larger and longer ferrite rod coil for the LW and MW bands together like the modern shortwave receivers. The OSC IF coil transformer measures a higher inductance that will receive the 144 kHz to 281 kHz bands. The longwave band is like the AM broadcast band, but lower in frequency range. And AM and LW is directional so a loop antenna is a must for better reception. The MW band uses a medium inductance ferrite rod coil around 60 to 175 turns and just like the LW band, the MW coil for modern shortwave radios has one for both LW and MW bands. The OSC IF coil transformer has a medium inductance measurement and is the same one used in most AM transistor radios

Propagation and Solar Activity is the main reason for SW broadcasting, and that's how

radios travel from all over the world. Depending on space weather conditions. The propagation for shortwaves are like this.

Daytime Propagation - Signals propagate from one place to another by the F1 and

F2 layers of the ionosphere. The low frequency signals from 3 MHz to 10 MHz are

mostly absorbed by the D Layer depending on the solar activity and the geomagnetic

field. Most of the distant stations in the daytime propagate well in the 9 MHz to 17

MHz frequencies. In the summer months when the solar activity is high the 18 MHz to

26 MHz bands become active and also the 10 meter bands.

Nighttime Propagation - Nighttime propagation occurs and the upper bands in the

10 MHz to 26 MHz signals get attenuated cause the F2 layer has disappeared and

all there is left is the 1.8 MHz to 10 MHz bands to listen to. All there is left is the

F Layer. When solar activity is high the propagation is still good for the 10 MHz to

30 MHz range. when the propagation is low to very low the band openings for 10

MHz to 30 MHz are very limited.

1.8 MHz to 7 MHz - Nighttime Propagation Is Unlimited, Daytime Propagation is

Limited. 7 MHz to 30 MHz - Nightime propagation is Limited, Daytime propagation is limited. Its best that in the nightime that you switch to SW1 3.5 MHz to 8 MHz and

for in the daytime you switch to SW2 8 MHz to 26 MHz when you want to hear

daytime signals. In the evening around in the summertime you can still use the

SW 2 bands depending on the solar activity and geomagnetic field. Nightime

- If you listen to radio at night you would need a bigger antenna over 10 to 150 feet in

length, Daytime - If you listen to radio in the daytime you need a 8 to 30 feet wire in

length.

Longwave Propagation - Longwave propagation is optimized at night at 6 PM to

1 AM in the Eastern parts of the USA. For the western part of the USA you need

to tune in at 1 AM to 6 AM in the morning. For the rest of the world you need to

listen to LW the same time from 6 PM to 1 AM you time. and for the western parts such as the Pacific 12 AM to 6 AM. This happens when the D layer gets sporadic and starts

to propagate the trans Atlantic and pacific DX LW signals via ground wave bouncing

off the curvature of the Earth off of sea water. Inland LW DX happens when signals

travel via groundwave by earth soil.

AM/MW propagation - In the daytime, The AM signals travel via groundwave limited

to only 300 miles or less. In the nightime the signals travel across the country

via skywave and groundwave. Transatlantic DX signals travel via groundwave and

skywave over salt water.

DRM reception is a mode for digital reception that requires a digital stream decoder to receive the AM transmission that modulates the digital stream via SW. If broadcasted in IBOC (HD Radio Mode) the transmission would be adjecent to the carrier. This is the same technique a radio teletype (RTTY) used in news agencies.

Answer 3

The process is very complicated, but I can simplify it here. A signal starts as a wave in the oscillator of the radio. You speak into the microphone, and this produces another wave at your voice frequency. These two signals go into the modulator, which uses the voice signal to encode the wave from the oscillator, or modulate it. This signal is sent out of the antenna. The receiver is like a transmitter in reverse (obviously), that decodes it, and sends the decoded signal into the speaker.

Answer 4

Summary: A radio transmitter works by converting electricity into radio-frequency energy, which is then converted to electromagnetic waves.

Block by block...

The most important components of a radio transmitter are the Oscillator and the Antenna. The oscillator makes the radio-frequency energy; the antenna converts it to electromagnetic waves for the receiving station to use. I say these are the most important components because you can build a whole radio transmitter with nothing but an oscillator and an antenna. There aren't many applications for such a transmitter--it can be a beacon, or if you turn it on and off fast enough you can send Morse code with it--but it's enough to put RF in the air.

The next important part is the Modulator. This is the thing that lets a radio station play music instead of just sending out radio waves--it causes the radio signal to change in a way a receiver can use. It can either change the intensity of the wave--amplitude modulation--or the frequency--frequency modulation.

They also put Amplifiers on radio stations, because you need a lot of power to transmit music or speech, and the oscillators made today don't put out very much of it. If you're listening to your radio and the announcer says he's on the "50,000 Watt KLMN" the amplifier is what gives him all that power.

Answer 5

Basic principle behind every radio is the process of modulation (superimposition of signals on carrier waves collectively called baseband signal) and demodulation of radio waves.

Answer 6

same as a standard fm/am radio transmitter, the difference is that it uses a much shorter wavelength

Answer 7

Same as any other [usually AM] radio, but at higher frequencies.

Answer 8

to listen to it