what function does squelch perform for a radio?
461540
The squelch establishes a threshold based off of the received signal strength to determine whether the received audio should be muted or not.\n\nIts use is to keep the receiver quiet when there is no intelligible signal to be received, or in other words, mute the static noise when no one is transmitting so the receiver doesn't become annoying to listen to.\n\nNormally, the squelch level is set just above the point of the ambient radio noise being received, so the receiver is quiet.  When a signal stronger than the squelch threshold is received, the squelch "opens" and you hear the audio through the speaker.\n\nThere are other schemes for squelching the unwanted noise, and sometimes unwanted transmissions of other users on a frequency.  Some include transmitting a sub-audible tone along with the audio (also known as CTCSS or PL), or prefacing each transmission with a quick series of DTMF (touch tones) numbers or a short burst of data.  Each of these signals the receiver to open the squelch for the duration of the transmission.
849670
not sure if you've heard of Winamp or not, but it has an impressive radio/net tuner built in.. even does satelite radio.. one of my favorite audio applications.
762445
More complex radar systems, like those used at airports, allow radio waves to be imaged on a computer screen. They send out a beam of radio waves (like a flashlight sends out light), collect the waves that reflect of off distant objects, and reconstruct the wave pattern into an image (like the eye does with light). The result is displayed for the operator to see.
481454
ADF's detect an electric field and a magnetic field which are perpendicular in space and their amplitudes vary sinusoidally with time. The magnetic field induces a voltage into the windings of the ADF loop antenna. By measuring the phase difference between the windings the ADF is able to determine the direction of the beacon. \n\nPutting beacons around the house and using ADF to navigate turns out to be expensive and inefficient as GPS and proximity sensors are available and work better.
580858
Spectrum analyzer.  See Berkeley Varitronics Systems BUMBLE BEE below has a handheld tool for wireless LAN frequencies of 2.4 GHz.  You can get other instruments for other frequencies -- some spectrum analyzers will frequency sweep.\n\nA very low cost solution, although not quantative, is to use a portable AM radio tuned away from a station and the volume turned up -- carry this around the room or use from your car's radio.\n\nSee the US Frequency Chart below.
298935
TRANSMITTER ,RECEIVER, ANTENNA COAX SWITCH, COAXIAL CABLE FOR ANTENNA, ANTENNA,  ANTENNA STRUCTURE. 2 EACH. MAKE A SYSTEM.\n\nOR\n\nTRANSCEIVER , COAX , ANTENNA, ANTENNA SUPPORT! 2 EACH. MAKE A SYSTEM.\n\n\nTRANSCEIVER COULD BE FM, OR AM.  AIRCRAFT USE AM FOR PLANE TO PLANE AND PLANE TO GROUND.  POLICE , FIRE, UTILITIES AND MOST LAND MOBILE USE NARROW BAND FM.  CB IS AM MODULATION.  THE  NEW CB IN HIGHBAND IS 900 MHZ FM THIS IS WHAT YOU CAN GET AT WALMART IN THE LITTLE WALKI-TALKIES! WITH A 6 MILE RANGE!\n\nA SYSTEM IS SYMPLY A SENDING STATION AND A RECEIVING STATION.  IT CAN BE VERY COMPLEX OR AS SIMPLE AS A SET OF WALKIE TALKIES.  A SYSTEM IS A FUNCTIONAL DEFINITON FOR SOMETHING THAT WORKS!\n\nA SYSTEM COULD REFER TO A SYSTEM THAT YOU USE AROUND YOUR HOME TO KEEP IN COMMUNICATION WITH YOUR FAMILY!  OR IT COULD BE A SYSTEM THAT A BUSINESS USES TO STAY IN TOUCH WITH ITS EMPLOYEES!  A SYSTEM IS JUST A FUNCTIONAL DEFINITION OF A OPERATIONAL "SYSTEM". IT IS THAT SIMPLE!\n\nHOPE THAT CLEARS THAT UP FOR YOUR!\n\n\nDO ME A FAVOR AND VOTE TO BREAK THE TIE ON YOUR QUESTION ON RADAR AS A DISTANCE FINDER IF YOU HAVENT CHOSEN A ANSWER YET SO THAT ONE OF US WILL GET OUR POINTS !\n\n\nTHANK YOU!!!
530967
Like that of a intercome system. Your voice is amplified and sent down the signal wire (Tip - old technology). The common wire (Ring).
363414
it uses mobile wireless communication to communicate with other modems/receivers. It operates through GSM frequency, the same frequency GSM mobile phones use.
170564
try\n\nhttp://www.radioreference.com/modules.php?name=RR&ctid=28
199934
An echo sounder consists of a transmitter, which emits an ultrasonic pulse, and a receiver, which detects the pulse after reflection from the seabed. The time between transmission and receipt of the reflected signal is a measure of the depth of water. Fishing boats use echo sounders to detect shoals of fish and navies use them to find enemy submarines.
588321
No, it is not.\n\nAn antennae is a reacive circuit normally tuned to resonance at the transmitting frequency. In such case it will produce a damped series of oscillations when energised by a pulse. Theoretically it would not, if the energising signal was a perfect sine wave and cut off at the zero crossing point exactly. However no wave generated by a 1Ghz oscillator will be a perfect sine wave and therefore the tendency of the antenna circuit to oscillate will produce at least a blurring or extension of the waveform beyond the single cycle.\nIf the antenna was not resonant then it would produce reflective waveforms and these will oscillate until their energy is dissipated. \nConsidering the fact that it is not possible to create any antenna system (including the transmission line) without some SWR, then the answer to your question is no.
709893
They use a frequency within the VHF band depending on where in the world they are or even the area that they are in and who else has local frequencies reserved.\nThe biggest problem that you will come across is that they scramble the signal, so even if you can find the frequency which is quite easy with a hand held scanner, you wont be able to hear what they say. Sorry. Would be fun to know though.
257535
It does echo. Mythbusters (the TV show) debunked the myth. Using a bunch of expensive studio equipment, they found that yes, it does echo, but the quack closely resembles the echo, enveloping it.
74707
What you hear is 1K (1000kilohertz) signal.  Broadcasters use that tone to adjust equipment.  So it's handy and has been used since the beginning.  A few years back it also used to be used for the Emergency Broadcast System.
945980
Hook up your computer to a radio transmitter.
95364
Looking at your various questions, it appears that you are trying to figure out how to transmit square pulses.\n\nAs other posters have noted, a square pulse is the sum of an infinite Fourier series containing the fundamental frequency and every other harmonic.  But since all real systems are band-limited, this is impossible in real-life.\n\nAn adequate representation of a square wave can be created with three to nine harmonics.  Check this link, a little over half way down there is an applet which allows you to view a square wave recreated from limited number of harmonics.\n\nhttp://www.jhu.edu/~signals/phasorlecture2/indexphasorlect2.htm\n\nIf you have a bandlimited system, then you cannot transmit a perfect square pulse.  You can, however, recreate the pulse using digital methods on the receiving end.  Check page 3 of this presentation for the concept:\n\nhttp://www.freedomuniversity.net/ColoradoTechUniv/EE645/LessonNotes/2006/Lesson1/Chapter1web.pdf\n\nSo, possible approach, using your band-limited system, transmit the best representation of the square pulse possible.  At the receiving end, typically you would use a matched filter and integrate the received signal over the sampling frequency.  The output is then compared to a threshold to determine if 0 or 1 is transmitted.  Based on this, you can recreate your square wave.\n\nHope this helps.
239908
TRANSMITTER ,RECEIVER, ANTENNA COAX SWITCH, COAXIAL CABLE FOR ANTENNA, ANTENNA, ANTENNA STRUCTURE. 2 EACH. MAKE A SYSTEM.\n\nOR\n\nTRANSCEIVER , COAX , ANTENNA, ANTENNA SUPPORT! 2 EACH. MAKE A SYSTEM.\n\n\nTRANSCEIVER COULD BE FM, OR AM. AIRCRAFT USE AM FOR PLANE TO PLANE AND PLANE TO GROUND. POLICE , FIRE, UTILITIES AND MOST LAND MOBILE USE NARROW BAND FM. CB IS AM MODULATION. THE NEW CB IN HIGHBAND IS 900 MHZ FM THIS IS WHAT YOU CAN GET AT WALMART IN THE LITTLE WALKI-TALKIES! WITH A 6 MILE RANGE!\n\nA SYSTEM IS SYMPLY A SENDING STATION AND A RECEIVING STATION. IT CAN BE VERY COMPLEX OR AS SIMPLE AS A SET OF WALKIE TALKIES. A SYSTEM IS A FUNCTIONAL DEFINITON FOR SOMETHING THAT WORKS!\n\nA SYSTEM COULD REFER TO A SYSTEM THAT YOU USE AROUND YOUR HOME TO KEEP IN COMMUNICATION WITH YOUR FAMILY! OR IT COULD BE A SYSTEM THAT A BUSINESS USES TO STAY IN TOUCH WITH ITS EMPLOYEES! A SYSTEM IS JUST A FUNCTIONAL DEFINITION OF A OPERATIONAL "SYSTEM". IT IS THAT SIMPLE!\n\nHOPE THAT CLEARS THAT UP FOR YOUR!\n\n\nDO ME A FAVOR AND VOTE TO BREAK THE TIE ON YOUR QUESTION ON RADAR AS A DISTANCE FINDER IF YOU HAVENT CHOSEN A ANSWER YET SO THAT ONE OF US WILL GET OUR POINTS !\n\n\nTHANK YOU!!! \n\n\nSEE THE FIRST QUESTION!\nYOU ASKED THIS TWICE\n\nAPS\n\n\nhttp://answers.yahoo.com/my/profile;_ylt=AkNRDPHU4.dwE9DX6LQDRNgezKIX?show=AA10836052\nPOGI N POGI 88 YOU HAVE A PROBLEM YOU ARE NOT SELECTING THE ANSWERS!  YOU ASK QUESTIONS BUT DO NOT SELECT THE ANSWER! BECAUSE I AM SELECTING THE ANSWERS SO FAR FOR YOU ON YOUR QUESTIONS! ME! GET WITH THE PROGRAM! YOU ARE RUNNING OUT OF POINTS! SELECT THE BEST ANSWER YOURSELF! DO NOT LET IT HAVE TO GO TO VOTE! DO YOUR DUTY!  YOU HAVE NO POINTS THIS WEEK!  GET WITH THE PROGRAM!  IF YOU ASK QUESTIONS SELECT THE ANSWER OR DO NOT ASK!\n\nTHERE ARE WAYS OF TELLING!