Can we modulate radio wavelength?

[Moreno]

Short waves have advantage when we need to code a lot of data. But they can't regularly spread for a large distances. (unless we use an expensive satellites).

Long waves on other hand can spread for thousands of kilometers, but cannot code a lot of data.

 

Is there an absolute connection between frequency and wavelength? Can we modulate short waves somehow to increase their effective wavelength? For example, wavelength depends on phase velocity.

Does it mean that modifying phase velocity we can change wavelength regardless of frequency?

Edited July 2, 2017 by Moreno

[studiot]

Short waves have advantage when we need to code a lot of data. But they can't regularly spread for a large distances. (unless we use an expensive satellites).

Long waves on other hand can spread for thousands of kilometers, but cannot code a lot of data.

 

Is there an absolute connection between frequency and wavelength? Can we modulate short waves somehow to increase their effective wavelength? For example, wavelength depends on phase velocity.

Does it mean that modifying phase velocity we can change wavelength regardless of frequency?

 

Yes, this is good thinking.

 

Frquency modulation is the most common form of phase modulation, but not the only one.

 

If, however, you want to pack more data in you need to employ a variety of methods, in multiplexed mode.

This is how television tranmission used to work, before digital.

 

Current so called broadband internet signals also use multiplexing, in this case time domain multiplexing.

[swansont]

 

Is there an absolute connection between frequency and wavelength?

 

 

Their product is the speed of propagation. For EM waves, this is c

[EdEarl]

You can modulate both sidebands with different messages to increase the bandwidth.

[Moreno]

 

Yes, this is good thinking.

 

Frquency modulation is the most common form of phase modulation, but not the only one.

 

If, however, you want to pack more data in you need to employ a variety of methods, in multiplexed mode.

This is how television tranmission used to work, before digital.

 

Current so called broadband internet signals also use multiplexing, in this case time domain multiplexing.

 

I meant some waves in which we could pack as much data as in GHz frequency, but which can propagate

as well as 1KHz-30MHz frequency. The methods you've mentioned still don't offer that possibility?

[rangerx]

 

I meant some waves in which we could pack as much data as in GHz frequency, but which can propagate

as well as 1KHz-30MHz frequency. The methods you've mentioned still don't offer that possibility?

 

Time.

 

The longer the wave, the greater the time between cycles. Long wave AM (RTTY for example) carry perhaps 300 baud of data (at best), whereas shorter waves carry much more data (gigs) in a shorter time span.

 

A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. Packets of data may be re-interpreted if they're incomplete, but if the spaces are too long or broadly distorted due to Doppler shift, auroras, storms etc., they're dropped altogether. In AM networks, solar/terrestrial conditions provide only small windows of opportunity. Sometimes not at all, whereas FM is constant. Even if AM could be crammed with data reliably, the overall bandwidth in any given day would be much less.

[Moreno]

 

Time.

 

The longer the wave, the greater the time between cycles. Long wave AM (RTTY for example) carry perhaps 300 baud of data (at best), whereas shorter waves carry much more data (gigs) in a shorter time span.

 

A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data. Packets of data may be re-interpreted if they're incomplete, but if the spaces are too long or broadly distorted due to Doppler shift, auroras, storms etc., they're dropped altogether. In AM networks, solar/terrestrial conditions provide only small windows of opportunity. Sometimes not at all, whereas FM is constant. Even if AM could be crammed with data reliably, the overall bandwidth in any given day would be much less.

 

What if we take a short GHz wave and change its phase velocity? Will it lose ability to carry lot of data?

Will it gain ability to spread for a longer distance?

[Chopsticks]

Wavelength, frequency, and phase velocity, and how a signal spreads over distance, if you pick one the others are basically fixed. C=f/w, velocity depends on frequency and refractive index (1.0 almost always), and interaction with antennas/lenses/walls is basically wavelength. 

What you can vary is modulation and bandwidth. IIRC, bandwidth is independent of carrier frequency, so a 20 kHz audio signal requires 20 kHz whether the carrier is 100 kHZ or 20 Ghz.

The practical answer to the initial question is modulation can put the same data in low or high frequency carrier. But, the hardware needed gets much more difficult as the ratio of carrier/mod frequency gets larger.  20 khz signal on 20 Ghz carrier is .00??1% bandwidth, 20 khz signal on 100 khz carrier is 25ish % and much harder.

Course, this is still neglecting things like a long wavelength needs long antennae to pick up, some frequencies get absorbed by atmosphere more quickly, and the dynamic range of the signal voltage

 

 

[Moreno]

Here some authors describe "an infinite wavelength resonant antenna".

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.132.4668&rep=rep1&type=pdf

If we have a radio wave with infinite wavelength, as they said, what would be the propagation properties of such radio wave? And how much data can it encode/carry?