Quantcast ADVANTAGES OF FSK OVER AM

Share on Google+Share on FacebookShare on LinkedInShare on TwitterShare on DiggShare on Stumble Upon
Custom Search
 
  
 
2-8 Figure 2-4B.—Two methods of frequency-shift keying (fsk). FREQUENCY-SHIFT KEYING IN MASTER OSCILLATOR CIRCUIT. ADVANTAGES OF FSK OVER AM.—Frequency-shift keying is used in all single-channel, radiotelegraph systems that use automatic printing systems. The advantage of fsk over on-off keyed cw is that it rejects unwanted signals (noise) that are weaker than the desired signal. This is true of all fm systems. Also, since a signal is always present in the fsk receiver, automatic volume control methods may be used to minimize the effects of signal fading caused by ionospheric variations. The amount of inherent signal-to-noise ratio improvement of fsk over AM is approximately 3 to 4 dB. This improvement is because the signal energy of fsk is always present while signal energy is present for only one-half the time in AM systems. Noise is continuously present in both fsk and AM, but is eliminated in fsk reception. Under the rapid fading and high-noise conditions that commonly exist in the high frequency (hf) region, fsk shows a marked advantage over AM. Overall improvement is sometimes expressed as the RATIO OF TRANSMITTED POWERS required to give equivalent transmission results over the two systems. Such a ratio varies widely, depending on the prevailing conditions. With little fading, the ratio may be entirely the result of the improvement in signal-to-noise ratio and may be under 5 dB. However, under severe fading conditions, large amounts of power often fail to give good results for AM transmission. At the same time, fsk may be satisfactory at nominal power. The power ratio (fsk versus AM) would become infinite in such a case. Another application of fsk is at low and very low frequencies (below 300 kilohertz). At these frequencies, keying speeds are limited by the "flywheel" effect of the extremely large capacitance and inductance of the antenna circuits. These circuits tend to oscillate at their resonant frequencies. Frequency-shifting the transmitter and changing the antenna resonance by the same keying impulses will result in much greater keying speeds. As a result, the use of these expensive channels is much more efficient. Q-1. What are the two types of angle modulation? Q-2. Name the modulation system in which the frequency alternates between two discrete values in response to the opening and closing of a key? Q-3. What is the primary advantage of an fsk transmission system? Frequency Modulation In frequency modulation, the instantaneous frequency of the radio-frequency wave is varied in accordance with the modulating signal, as shown in view (A) of figure 2-5. As mentioned earlier, the amplitude is kept constant. This results in oscillations similar to those illustrated in view (B). The number


Electrical News
Creating an 8x8x8 3D LED Cube: The Base PCB
Creating an 8x8x8 3D tri-color LED cube from the ground...
eetimes.com
Allocating MCU Resources Accurately
When you need a new MCU and new I/O for...
eetimes.com
Experts Call for Secure Sensors
Sensor nodes are the most vulnerable point of attack in...
eetimes.com
AMD Integrates X86, GPU & I/O
Early next year, AMD will ship Carrizo, its most integrated...
eetimes.com
Test Your Way to a Better IoT
Better design and test procedures will lead to much lower...
eetimes.com
12 Startups I Saw at Demo
The consumer Internet of Things sector is getting crowded and...
eetimes.com
Megachips: Japan's Best Kept Secret
In a recent interview with EE Times, Megachips' president and...
eetimes.com
Intel Expects 2015 Mobile Speedup
Intel is back on track with mobile, company officials said...
eetimes.com
Culture Is King in Job Search
Programmers, web developers, and software engineers often assume that technical...
eetimes.com
LEDs Go Color-Temperature & Tunable
The LED manufacturer Everlight introduced what it calls the world's...
eetimes.com
Drag An Oscilloscope Through 6km of Mud?
Sponsor Dave in the 2014 Sydney Mud Run, proceeds go...
eevblog.com
Friday Quiz: More Radar
An EE Times reader submitted our second Friday quiz about...
eetimes.com
Dick Smith – Amateur Radio & Adventure
Dick Smith talks about how he got started, the early...
eevblog.com
Want to Present a Paper at ESC Boston 2015?
If you are interested in presenting a paper on the...
eetimes.com
Transparent Car Shows Automotive's Future
TE Connectivity's clear-plastic, full-size model car shows the latest advances...
eetimes.com
Why No One Leaves Linear Technology
Why culture makes Linear Tech a winner....
eetimes.com
The Messe U-Bahn Crush Business Indicator
Electronica's healthy glow means good things for Europe's electronics sector....
eetimes.com
Automotive Industry Drives Chip Demand
Among all major end use-applications for integrated circuits, the automotive...
eetimes.com
Power Week: Duracell Buyout Tied to Wireless Power, EVs?
The acquisition of the Duracell battery brand by Warren Buffett's...
eetimes.com
What Are You Wearing?
The wearables market is at $6B this year and is...
eetimes.com
 


Privacy Statement - Copyright Information. - Contact Us

comments powered by Disqus

Integrated Publishing, Inc.
9438 US Hwy 19N #311 Port Richey, FL 34668

Phone For Parts Inquiries: (727) 755-3260
Google +