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
Could India's Analog Wafer Fab be Moving South?
Cricket Semiconductor, a company set up with the purpose of...
eetimes.com
Apple Watch Tear Down Reveals European Chips
The Apple Watch, is the trailblazer of a wearables equipment...
eetimes.com
Ethernet Standards Ramp Up For Faster IT
The Ethernet Alliance and UNH-IOL hosted a plugfest to test...
eetimes.com
3-D Fingerprint Scanner Beats Apple's
The University of California at Davis, in cooperation with the...
eetimes.com
No Respect!
Every now and then, you see someone doing something, and...
eetimes.com
Friday Quiz: Name That 1994 Test Instrument
If you can remember back to 1994, then take a...
eetimes.com
It's a Bird. It's a Plane! It's a Drone!!
EE Times has gathered a panel of drone experts, including...
eetimes.com
Firework display as seen through the eyes of a drone
Have been thinking about purchasing a drone? If so, watching...
eetimes.com
FinFETs + FD-SOI Proposition: May Save Power
Ron Martino, vice president of application processors and advanced technology...
eetimes.com
Biodegradable Electronics Debut
Single crystal silicon transistors operating in the same microwave frequency...
eetimes.com
DesignCon 2016 Abstract Deadline Extended
You now have until Wednesday, July 8 so get your...
eetimes.com
IBM Makes Lake George World's Smartest Lake
Over 60 researchers, including ones from IBM and Rensselaer Polytechnic,...
eetimes.com
Developing Safety Certified Code for Industrial Systems
The right design framework and RTOS can help simplify and...
eetimes.com
Intel President, Execs Step Down
Intel President Renee James is among several top executives who...
eetimes.com
High-Speed Converters Aid Record Terabit Field Trial
Ultra high-speed digital-to-analog and analog-to-digital converters from Socionext Inc. (Yokohama,...
eetimes.com
Speech Recognizer / Synthesizer Shield for Arduino & Other MCUs
A Kickstarter project the just launched promises a rather interesting...
eetimes.com
Want a Free GPAK4 Mixed-Signal FPGA Development Kit From Silego?
25 GPAK4 mixed-signal FPGA development kits will be given by...
eetimes.com
IMB-GlobalFoundaries Deal Finalized
Following final approval by U.S. regulators, IBM closed the sale...
eetimes.com
20% Discount for ESC Silicon Valley 2015 Using Secret Code
Max's top-secret-squirrel code for the forthcoming ESC Silicon Valley 2015...
eetimes.com
UWAS: Playing Hide and Seek with Drones
The Paris Air Show (June 15-21) was rich in drone...
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 +