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Topic: Varicode

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	PSK31 - Wikipedia, the free encyclopedia
		Martinez initially called his creation "varicode", because it uses variable length encodings (Huffman codes) to represent characters.
		Varicode was designed so that the more frequently occurring characters had shorter encodings and the rarer characters used the longer encodings, a coding scheme similar to Morse code.
		The 31.25 Hz bandwidth was chosen because transmitting Varicode at a normal typing speed of about 50 words per minute needs a bit-rate of about 32 per second.
	en.wikipedia.org /wiki/PSK31 (458 words)

	varicode - a definition from Whatis.com
		- Varicode is a method of binary character encoding in which the number of bits for each character is not fixed, but varies for each character depending on how often that character occurs in general usage.
		Varicode is most effective in weak-signal data transmission modes, such as PSK31 (phase-shift keying at a data speed of 31.25 baud or state changes per second) and MFSK (multiple frequency-shift keying), especially in radio-frequency (RF) wireless systems.
		In varicode, the characters that appear most frequently, such as the lowercase letter e, have the shortest binary representations.
	searchnetworking.techtarget.com /sDefinition/0,,sid7_gci1038114,00.html (331 words)

	[No title] (Site not responding. Last check: 2007-11-03)
		The IZ8BLY MFSK Varicode ======================== © 2000 Nino Porcino IZ8BLY & M. Greenman ZL1BPU Ver 1.0, 10 July 2000 The MFSK varicode is designed for a quite different application from the familiar code designed by G3PLX for PSK31.
		Because of the different way in which the idle condition is signalled, this code is able to utilise sequences of bits containing more than two consecutive zeros.
		The numbers in square brackets are the ASCII value in decimal, the following binary number is the varicode, MSB first, and includes the following "00" which is the end of character framing symbol.
	www.qsl.net /zl1bpu/MFSK/Varicode.txt (378 words)

	e56
		In addition to the 31.25 Hz bandwidth, the use of the Varicode is a second characteristic of this modus.
		The Varicode alfabeth was derived by Peter from a huge pile of English texts.
		Useful to know for practice; as a result of the construction of the Varicode alfabeth, the transmission rate for the small characters (non-capitals) is twice the rate of the capitals.
	www.home.zonnet.nl /laar60/e56.htm (1629 words)

	MFSK16 (Site not responding. Last check: 2007-11-03)
		The strength of the varicode is that the alphabet is essentially infinitely expandable.
		The MFSK16 varicode is not the same as the PSK31 varicode, although the technique is similar.
		Another important advantage of using a varicode is that the stream of data can be much more quickly resynchronized in case of errors, than is possible with other systems, and so a minimum of data is lost.
	www.saraclub.net /new_page_61.htm (3408 words)

	The IZ8BLY MFSK Varicode (Site not responding. Last check: 2007-11-03)
		The MFSK varicode is designed for a quite different application from the familiar code designed by G3PLX for PSK31.
		The super-alphabet characters are not part of the MFSK 2000 Specification, except that they will be ignored when received by the specified receiver.
		Here follows the Varicode Table, (cut directly from the source code) in order of assessed character frequency.
	www.qsl.net /zl1bpu/MFSK/Varicode.htm (396 words)

	ARRLWeb: PSK31--Has RTTY's Replacement Arrived? (Site not responding. Last check: 2007-11-03)
		The Varicode does this by using "00" to represent a gap.
		The Varicode is carefully structured so that two zeros never appear together in any of the combinations of 1s and 0s that make up the characters.
		Thanks to the structure of the Varicode, however, the phase transitions are also mathematically predictable, so much so that the PSK31 software can quickly synchronize itself when you tune in during the middle of a transmission, or after you momentarily lose the signal.
	www.arrl.org /tis/info/HTML/psk31 (4260 words)

	varicode - a Whatis.com definition
		Varicode is a method of binary character encoding in which the number of bits for each character is not fixed, but varies for each character depending on how often that character occurs in general usage.
		In the event of an error, the data stream can be re-synchronized almost immediately between the transmitting station and the receiving station.
		Another advantage is that the character set can be indefinitely expanded, because there is no imposed limit to the number of bits that a character can contain.
	whatis.techtarget.com /gDefinition/0,294236,sid40_gci1038114,00.html (313 words)

	PSK31
		The Varicode does this by using "00" to rep resent a gap.
		The Varicode is carefully structured so that two zeros never appear together in any of the combinations of Is and Os that make up the characters.
		Peter's answer was to use the DSP capabilities of the common computer sound card to create an audio signal that shifted its phase 180o in sync with the 31.25 bit-per-second data stream.
	www.kwarc.org /tech/psk31.htm (2850 words)

	PSK31 transmit beacon
		In PSK31 (1's) are represented by a tone with no phase shift compared to the previous bit and (0's) are tone with a 180 degree phase shift relative to the phase of the previous bit.
		Since the varicode symbol can be as short as 1 bit to as long as 10 bits, I stored the table in the PIC's 14 bit wide flash memory area.
		The tone level can be set to the desired volume by adjusting the 20k pot in the output circuit.
	www.ringolake.com /pic_proj/PSK31/pic_psk31.html (632 words)

	WinPSK 31-16 (Site not responding. Last check: 2007-11-03)
		This is why one should not use all uppercase when using PSK31 since the varicode was optimized for lowercase letters.
		The varicode words from the table are sent msb first.
		The Varicode word is serialized and converted into a 2 bit symbol before being sent to the differential phase state machine which will determine the next signal phase based on the present phase and the new symbol.
	207-207-72-42.ip.theriver.com /bytheway/whitepapers/Digital_QST.htm (3219 words)

	PSK31 Audio Beacon Source Code
		The bits constituting the Varicode character being sequentially presented for modulation are inspected on a bit-by-bit basis at each 31ms bit processing window.
		If the "next bit" of the varicode character to be processed is a "0", the scaling process is turned on at mid-bit position and the remaining 7 carrier cycles of waveform construction occurring in the bit-processing window get scaled per the cosine look-up table.
		This effectively brings the amplitude of those seven sine waves progressively down to zero, at which point the phase of the carrier is reversed (by changing to a different sine wave look-up table — one that is 180-degrees out of phase from the other one.)
	www.njqrp.org /digitalhomebrewing/psk31beacon/beacon_source.html (1822 words)

	MFSK (Site not responding. Last check: 2007-11-03)
		MFSK16, like PSK31, is based on a Varicode, which, unlike most such alphabets, assigns a different number of bits to different characters, so that more frequently used characters have fewer bits and are therefore sent faster.
		Another important advantage of using a varicode is that the stream of data can be much more quickly re-synchronized in case of errors, than is possible with other systems, and so a minimum of data is lost.
		The MFSK Varicode is slightly more efficient than others, since smaller codes are available.
	www.zl3gp.co.nz /zl3gp/mfsk.htm (1266 words)

	[No title]
		Carrier power is brought to zero during phase reversals in order to ; provide cleaner spectrum during phase reversals.
		; ; (3) When a 31ms window is reached (63, 31 or 15 cycles of the carrier, corresponding ; to 2kHz, 1 KHz, or 500 Hz, respectively), the PSK bit is processed by shifting out the Varicode character bits.
		The bits ;for the varicode are to be shifted out MSB-first for both bytes, with the first byte ;in the table for each character being the first one to be sent.
	www.njqrp.org /digitalhomebrewing/psk31beacon/audiopskv2.txt (870 words)

	MFSK16 vs PSK31 - Ionospheric Simulation (Site not responding. Last check: 2007-11-03)
		G3PLX QPSK31, 31.25 baud differential 4PSK with varicode and FEC.
		IZ8BLY PSK63F, 62.5 baud differential 2PSK with varicode and FEC.
		Other modes have been tested and the results can be viewed on Johan's Simulator page.
	home.teleport.com /~nb6z/compare1.htm (1355 words)

	EI7IS (Site not responding. Last check: 2007-11-03)
		PSK31 is a digital mode designed by Peter Martinez G3PLX for live keyboard QSO's (the same type operation as RTTY).
		The mode uses a transmission speed of 31.25 baud using varicode caracter coding what provides a speed of 50 words per minute (very few people can type faster than this).
		The varicode character set has varying data lengths for each character with the most commonly used letters having the shortest data length.
	www.searg.com /ei7is/digimode_psk.php (195 words)

	[No title]
		The transmission is always at 31.25 baud, with a variable length code (Varicode), where characters used more often have shorter bit codes.
		As a result, the mean transmission rate is about 50 words per minute (wpm).
		Standard Varicode has 128 codes (up to 10 bits), for standard Ascii characters, but there is also an extended version, with 256 codes (up to 12 bits each).
	web.tiscali.it /vcoletti/radio/diz_psk31.html (339 words)

	WB4DPC's PSK31 Page
		It was designed by Peter G3PLX, that betters SLOWBPSK, an idea and implementation of Pawel SP9VRC amd is based on the RTTY mode of operation.
		It is useful for live keyboard to keyboard QSO that works at 31.25 bauds, that uses varicode caracter coding what gives 50wpm.
		It is easy to use and monitor, which gives very good copy under low Eb/No numbers and is thus suitable for QRP.
	www.mshepp.com /psk31.htm (170 words)

	PSK Detector (Site not responding. Last check: 2007-11-03)
		The decoder uses the most modern digital PLL synchronization technology for bit synchronization and a neural network for detection.
		It prints PSK varicode characters on the screen.
		It searches the CW transmission in the range of the given frequency boundaries.
	www.scancat.com /skysweeppro/psk_detector.htm (394 words)

	Amateur Radio (Site not responding. Last check: 2007-11-03)
		PSK31 (Phase-Shift-Keying 31 Hz) is a relatively new digital mode that was introduced in the late 1990's by an Amateur Radio operator, Peter Martínez (G3PLX), from Great Britain.
		PSK31 uses the digital signal processing (DSP) capabilities of a computer sound card (via a special sound card interface to the radio) to interpret the varicode transmitted or received by a radio which has the audio frequency shifted 180 degrees at a bit rate of 31 Hz (actually it's 31.25 Hz).
		In theory, it may sound complicated but in practice it's a fairly simple-to-use mode and it's similar to an online chat forum found on the Internet.
	www3.telus.net /fredchen/psk (202 words)

	Club Meeting
		Thus PSK31 can cut through static and work weak signals.
		Peter Martinez, G3PLX, wrote a "Varicode" coding system, which he considered an extension of Morse Code, for PSK31.
		He wrote the first popular PSK31 software program, also called PSK31.
	www.brainerdham.org /2001/4-26-2001-meeting.html (584 words)

	RTTY Software : Software: RTTY
		MMvari - MMVARI is a multi-Mode SoundCard Ham (Amateur) Radio program for receiving and transmitting the RTTY-PSK-FSK-MFSK modes.
		The program was written to experiment with the efficiency of transmitting Japanese and East Asian languages (HL/BV/BY) using the VARICODE
		RCKRtty - RCKRtty is a comprehensible program for logging and administration of RTTY, PSK31, Pactor, Amtor and CW-QSO's with simultaneous control of transceiver and real-time operation with Packet-Radio.
	www.dxzone.com /catalog/Software/RTTY (500 words)

	PSK 31 and your soundcard (Site not responding. Last check: 2007-11-03)
		Three controls are used on the Soundblaster mixer control panel
		Varicode character set — yields ~50 wpm English
		Receiver tuning must be within a few Hz
	www.ggw.org /~xarc/XARC_PSK31.htm (377 words)

	The KS4VA Web Site
		PSK31 is my favorite mode, and it got me back in to ham radio after many years of separating my day job (RF Engineering) from my hobbies.
		For me, PSK31 is is the perfect blend of engineering hi-tech (extremely narrow band QPSK, Varicode coding, convolutional encoder, DSP Panoramic AF Demodulation, and a Viterbi decoder) that is so elegantly implemented, that a QRP transceiver kit can be bought for just $49 and provide inter-state digital communications on a modest antenna.
		I am an ElectroMagnetic Compatibility Engineer, with my own lab and engineering consulting business.
	www.ks4va.com (214 words)

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