DX or "skip" signals

D.X is a code given for long distance signals, say a few thousand kilometres. A Skip signal is a signal that travels in the air to the Ionosphere and bounces off that and back to the ground, covering thousands of kilometres in most cases. Maybe it lands on the other side of the world or interstate or intercontinental. Skip only occurs in the VLF, LF, MF, HF and part of the VHF spectrum. Signals above 50MHz to 60MHz don't always bounce off the Ionosphere. The Ionosphere is in layers and changes a bit at times, here is a diagram/explanation:

Part of the atmosphere is ionised by solar radiation. This in-turn causes radio waves to be bent back down towards earth. However, radio waves can be reflected and refracted off the troposhpere as well.

In the VHF/UHF region of the radio spectrum there are different types of signal propagation. These are termed differently because the ionosphere is split up into layers from D to F. For instance, 'Sporadic E' is a type of propagation that can cause VHF waves to travel more than 1000km which occurs at the 'E' layer. 'Troposphere Ducting' is another type that occurs, that is also termed temperature inversion. Different temperatures between masses of air influence this, and commonly occur along the coast.

Signals can travel over 20,000km (32,000 miles) with the correct aerial combinations and sunspot conditions. The sun influences radio skip quite a lot. Linear Amplifiers can also help of course, but are not legal on CB. Improperly tuned and operated systems with amplifiers can cause serious interference to Television, Radio and electronic micro computer systems. Wind screen wipers on a car can be activated by powerful linear amps! Auto engine management systems can but may not (and generally do not) fault due to Radio Frequency Interference (RFI).

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This Web page was last updated on Friday September 21, 2001

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