General/Chapter 5 Study Guide - Revision history

Admin: /* Chapter 6: Digital Modes */

2016-06-15T08:28:42Z

Chapter 6: Digital Modes

← Older revision		Revision as of 08:28, 15 June 2016
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	** "Remember to match the low-pass filter's impedance with the characteristic impedance of the feed line iti s inserted into")		** "Remember to match the low-pass filter's impedance with the characteristic impedance of the feed line iti s inserted into")
	** Impedance! Not inductance!		** Impedance! Not inductance!

	~~=Chapter 6: Digital Modes=~~



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2016-06-15T08:28:04Z

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← Older revision		Revision as of 08:28, 15 June 2016
Line 507:		Line 507:
	** "Remember to match the low-pass filter's impedance with the characteristic impedance of the feed line iti s inserted into")		** "Remember to match the low-pass filter's impedance with the characteristic impedance of the feed line iti s inserted into")
	** Impedance! Not inductance!		** Impedance! Not inductance!

			=Chapter 6: Digital Modes=



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Admin: /* Section 5.4: Receiver Structure */

2016-06-15T08:25:47Z

Section 5.4: Receiver Structure

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 ** This is imaging
 * it is important to match receiver bandwidth with operating mode because it gives the best signal to noise ratio
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Admin: /* Section 5.4: Receiver Structure */

2016-06-06T01:19:38Z

Section 5.4: Receiver Structure

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 * limiter: amplifies received signal until all amplitude modulation information (e.g., noise) is removed and only square wave remains, square wave of varying frequency
 * audio information: recovered by discriminator or quadrature detector (in place of the product detector in the AM/SSB/CW circuit)
 ===Section 5.4 Summary===
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Admin: /* Section 5.4: Receiver Structure */

2016-06-06T01:08:50Z

Section 5.4: Receiver Structure

← Older revision		Revision as of 01:08, 6 June 2016
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	==Section 5.4: Receiver Structure==		==Section 5.4: Receiver Structure==

			* Receivers have many more adjustments than transmitters

			Superheterodyne receivers:
			* mixing of signals is called heterodyning, leads to f1 +/- f2
			* superheterodyne receivers are sensitive to very weak signals
			* basic circuit:
			** RF signals are amplified and sent to mixer.
			** LO also sends signal to mixer.
			** signal at intermediate frequency IF is produced, filtered and demodulated.
			* iF filter removes nearby signals selectively
			* IF used because easier to tune filters/hi gain amps for single frequency
			* to convert signal at 14.250 to an IF of 455 kHz, local oscillator should be at 14.250 +/- .455 (13.795 or 14.705 MHz)
			* to cover entire 20 m band, 14.0 - 14.35, need local oscillator to tune from 13.545 MHz to 13.895 MHz
			* Demodulation of amplified IF signal is done by the product detector, a type of mixer
			* If AM being used, envelope detector is used for demodulation
			* Output of product or envelope detector is used to recover modulating signal
			* Product/envelope detector outputs audio signal
			* Front end of superheterodyne: antenna feeds into Rf amp. Mixer mixes signal from RF amp and from local oscillator. That is front end.
			* Front end processes weak signals at original frequency, so must owrk for wide frequency range and weak/strong signals
			* preselector sometimes used between antenna and RF amp to reject strong, out of band signals
			* these can fry a receiver if too strong, overwhelming circuitry
			* if additional sensitivity needed, preamplifier can be used
			* FM receivers: similar to superheterodyne, but key differences
			* FM only frequency matters
			* special non-linear amplifier called limiter replaces the linear IF amplifier
			* limiter: amplifies received signal until all amplitude modulation information (e.g., noise) is removed and only square wave remains, square wave of varying frequency
			* audio information: recovered by discriminator or quadrature detector (in place of the product detector in the AM/SSB/CW circuit)


	===Section 5.4 Summary===		===Section 5.4 Summary===

Admin: /* Section 5.3 Summary */

2016-06-06T01:03:04Z

Section 5.3 Summary

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 ** splatter
 ** excessive bkgd noise
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Admin at 01:00, 6 June 2016

2016-06-06T01:00:04Z

Show changes

Admin: /* Section 5.2: Radio's Building Bloccks */

2016-06-06T00:35:30Z

Section 5.2: Radio's Building Bloccks

← Older revision		Revision as of 00:35, 6 June 2016
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	* PM reactance modulator: amp and fixed-frequency oscillator feed into reactance modulator, output is phase modulated output		* PM reactance modulator: amp and fixed-frequency oscillator feed into reactance modulator, output is phase modulated output

	Summary:		===Section 5.2 Summary===
	* if a 3 kHz LSB signal has a carrier frequency of 7.178 MHz, it occupies 7.175-7.178 MHz		* if a 3 kHz LSB signal has a carrier frequency of 7.178 MHz, it occupies 7.175-7.178 MHz
	* if using 3 kHz USB signal on 20 m, how close to edge of band should carrier signal be? 3 kHz below edge of band		* if using 3 kHz USB signal on 20 m, how close to edge of band should carrier signal be? 3 kHz below edge of band

Admin: /* Section 5.1: Signal Review */

2016-06-06T00:35:12Z

Section 5.1: Signal Review

← Older revision		Revision as of 00:35, 6 June 2016
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	** CW - 100-300 Hz		** CW - 100-300 Hz

	Summary:		===Section 5.1 Summary===
	* The process that changes the phase angle of an RF wave to convey information is phase modulation		* The process that changes the phase angle of an RF wave to convey information is phase modulation
	* the process that changes instantaneous frequency of RF wave to convey information is frequency modulation		* the process that changes instantaneous frequency of RF wave to convey information is frequency modulation

Admin at 03:34, 28 May 2016

2016-05-28T03:34:16Z

← Older revision		Revision as of 03:34, 28 May 2016
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	* the mixing of two signals is called heterodyning		* the mixing of two signals is called heterodyning
	* in a VHF/UHF transmitter (FM), the stage that generates a harmonic of a low-frequency signal is the multiplier		* in a VHF/UHF transmitter (FM), the stage that generates a harmonic of a low-frequency signal is the multiplier

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