groundwaves help

[biferi]

I was looking all over the net and found groubnd waves are 30 kh to 3,000 kh

And LF and VHF and HF are ground waves.

But VHF is line of site I thought??

I went to wikapedia but I get more confused.

So let me ask this way?

I know at low freq it is groundwaves and as the waves get higher they are line of site.

And wen they get higher they are skywaves.

But I am trying to findout at what FREQ start groundwaves and start line of site waves and start skywaves??????????????????????

 

[dudmuck]

sky wave are those reflected by the upper layers of atmosphere called ionosphere, and usually apply to frequencies around 3 to 30MHz.

For line-of[-sight, think of sound waves: bass frequencies penetrate walls, yet high frequencies reflect off walls. Radio wave are same, the shorter the wavelength, the more they reflect off surfaces compared to penetrating them.

For ground waves, the most notable is AM broadcast since the wavelength is so long. If an AM broadcast transmitter keeps the same power output at night, then it will be heard alot further due to ground waves and D layer inactive at night.

 

[Robb]

Skywave - Wikipedia, the free encyclopedia

Figure 2-1. Ground waves and sky waves.

 

[mechanic]

And there is no definite line between one and the other as conditions can do "tricks" on the frequency. For example, because of the influence of the sun, especially when the sun spot activity is on the rise, the medium that the radio waves travel with or through, allows the waves to bounce long distances. This is typical of the 11 / 10 meter bands. Lack of sun, night time, make for better propagation on the lower frequencies.

73 mechanic