General/Chapter 8 Study Guide - Revision history

Admin: /* Section 8.3: Scatter Modes */

2016-07-15T17:33:28Z

Section 8.3: Scatter Modes

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 ==Section 8.3: Scatter Modes==
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2016-06-30T23:10:06Z

Section 8.2 Summary

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 * Significance of sunspot number with with respect to HF propagation is, '''higher''' sunspot number indicates '''better''' propagation at '''higher''' frequencies
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2016-06-30T23:01:50Z

Section 8.2: The Sun

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 * Use of data, experience, and software allows for predicting propagation and being alerted to sudden propagation changes
 * '''SFI''' - solar flux index - amount of 2800 MHz radio energy coming from sun
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2016-06-30T22:53:07Z

Section 8.1: Ionosphere

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 * Absorption increases with sunlight, ionization, more UV, and lower frequencies
 ===Section 8.1 Summary===
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2016-06-30T22:39:35Z

Section 8.1: Ionosphere

← Older revision		Revision as of 22:39, 30 June 2016
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	** Height of regions vary with season, TOD, latitude, solar activity		** Height of regions vary with season, TOD, latitude, solar activity
	** F2 is highest layer, reaches highest point at noon		** F2 is highest layer, reaches highest point at noon

			Reflection and absorption
			* Weak conduction of layers allows bending/refracting of waves
			* Layers of ionosphere can bend waves
			* Bending o waves depends on ionization level, and wave frequency
			* VHF/UHF waves hardly bent at all
			* HF waves bent, can be reflected back to Earth
			* Weaker bending requires lower takeoff angles, otherwise waves lost to space
			* '''Critical angle''' - angle above which all energy lost to space
			* '''Critical frequency''' - frequency above which all energy lost to space (if pointed straight up)
			* '''Ionosonde''' - device used for measuring reflection of radio waves by ionosphere
			* Absorption is the enemy of propagation
			* In D and E layers, waves pass through denser gas regions, absorbed as they are refracted
			* For HF bands, below 10 MHz, AM broadcast bands, the D layer completely absorbs radio waves
			* Absorption increases with sunlight, ionization, more UV, and lower frequencies


	===Section 8.1 Summary===		===Section 8.1 Summary===



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2016-06-30T22:35:59Z

← Older revision	Revision as of 22:35, 30 June 2016
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		==Section 8.1: Ionosphere==

		* Atmosphere gets thinner as you go further away
		* At 30 miles in altitude, gets thin enough that UV rays can knock electrons away from molecules
		* Gas is ionized by loss of electron, positively charged ion, negative free electron
		* Ion + electron respond to voltage, like electrons in conductor
		* Atmospheric layer - ionosphere - becomes weak conductor
		* Ionosphere extends to 300 miles above surface of Earth

		Regions:
		* ISS orbits 200 miles above Earht
		* Ionosphere arranged into multiple layers (D, E, F layers)
		* D layer - 30-60 miles, only present when illuminated by sun
		* E layer - 60-70 miles, similar to D region, lasts longer after sunset
		* F layer - 100-300 miles, least dens,e partially ionized at night
		** F1 layer/F2 layer - split during day, recombine at night
		** Height of regions vary with season, TOD, latitude, solar activity
		** F2 is highest layer, reaches highest point at noon


		===Section 8.1 Summary===

2016-06-27T07:23:08Z

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