FSQ
it stands for Fast Simple QSO mode
Author: ZL2AFP
Modulation scheme: Offset Incremental Frequency Keying or IFK
below is some features to this mode
IFK was developed by Steve Olney VK2XV. IFK+ (with code rotation) was proposed by Murray Greenman ZL1BPU and first used in DominoEX. IFK+ prevents repeated same tones without complex coding, and provides improved rejection of propagation-related inter-symbol interference. In the context of sync-less decoding, the IFK+ code rotation also prevents repeated identical tones, which could not have been detected by this method.
Efficient Alphabet
In FSQ, a relatively high typing speed at modest baud rate comes about because the alphabet coding is very efficient. All lower case letters and the most common punctuation can be sent in just one symbol, and all other characters (the total alphabet contains 104 characters) in just two symbols. (The alphabet is listed below). This is a simple example of a Varicode, where it takes less time to send the more common characters. The character rate is close to six per second (60 WPM), the same as RTTY, but at only 1/8th of the baud rate. (RTTY has only one bit of information per symbol, 7.5 symbols per character, and wastes a third of it's information on synchronization, and despite this, works poorly on HF).
No Sync
Another important factor in the design of FSQ is that no synchronising process is required to locate and decode the received characters. Lack of sync means that reception is much less influenced by propagation timing changes that affect almost all other modes, since timing is quite unimportant to FSQ; it almost completely eliminates impulse noise disruption; and it also contributes to very fast acquisition of the signal (decoding reliably within one symbol of start of reception). Fast acquisition removes the need for addition of extra idle characters at the start of transmission, and this leads to a very slick system. Add high resistance to QRM and QRN, thanks to the low baud rate, and you have a system so robust that it does not need error correction.
Arbitrary Sending Speed
Unlike most other modes (the exceptions are LF modes JASON and WSQ2), the FSQ receiver operates without needing any information about the sending speed. It will operate from 2 baud to 6 baud, and anywhere in-between, with no changes to settings. The speed tolerance of FSQ is very wide, in excess of 3:1. This is completely unique to FSQ, and gives operators great flexibility. The slower speeds are more robust and slightly more sensitive.
Four sending speeds are provided, 2, 3, 4.5 and 6 baud (approximately 20 to 60 WPM), which the receiver will decode with no change of settings. While the default speed is 6 baud, 4.5 baud is generally more reliable unless conditions are excellent.
Chat Operation
FSQ is designed for simple but effective 'Chat' operation, rather like phone text messaging or Skype™ chat; fast and easy to use. You don't use 'overs' as you would with a conventional digital or voice mode. It is highly suited to net operation. You just type a sentence and press Enter.
Directed Messaging Option
In addition, the FSQCall program, which operates FSQ, operates by default in an Active (Selective Calling) mode, which provides automated functions, and is also useful for net and emergency operation; as it provides network management, link establishment and order and reporting features. FSQCall is based on the FSQ digital modem, but adds numerous Selective Calling functions. It is now also widely used for chat QSOs because the protocol is easy to learn and it offers junk-free reception. Directed Messaging (Selective Calling) is described briefly below.
Directed Telemetry
Telemetry can also be directed to specific stations, or to all stations, and also to specific files at each station. Repeated telemetry frames sent to the same address and file places the data in the same file in sequential order. Telemetry can also of course be relayed, or sent from a third-party program via FSQCall.
Directed Image Transfer
FSQ can also be used to transmit and receive good quality pictures using special formats that have also been designed for NVIS propagation. The signals are analogue, of similar bandwidth to the FSQ digital transmissions. The transmissions can be used in Chat mode, and in Directed mode can be directed to specific (or all) stations for automatic reception. There are three modes: LO-RES COLOUR, HIGH-RES COLOUR and FSQ-FAX (B&W). Pictures can be transmitted from file photos, scanned documents, drawings and live shots from a web-cam!
Directed File Transfer
Files can be sent to a specific station, or all stations in range, and are saved automatically. The recipient is advised, and the sender notified if the file was saved safely. Files can be retrieved from a specific station, and you can also read brief or detailed listings of files available from any station running FSQCall V0.34 or later.
File transfer is secure in that you can't over-write important files, and you can't read files from anywhere else but the Shared folder on the other station's computer. While the file content is limited to standard text, it could be any type, for example .CSV, .HTML or .TXT, even program source code. If there seems to be an error in the file, simply request it again.
Error Correction
Because of the way it has been designed, FSQ is so robust that it does not need any error correction for normal QSOs. That means that transmissions are not slowed down or delayed by the heavy overhead imposed by error correction. Things are slightly different for Emergency Communications and Public Service applications, where there are many occasions when it is highly important for documents to be guaranteed 100% perfect, and FSQCall V0.40 now provides this capability.
From FSQCall V0.40, equipped with FSE V0.05, you can now send files with very strong Forward Error Correction, and be confident that they will be received 100% correct. FSE uses widely recognised Reed-Solomon error correction, and features human-readable transmissions and two coding strength levels, 15 or 30 errors per 255 character block.
More Technical Details
FSQ is essentially a speeded-up version of the weak-signal mode WSQ2, introduced in 2013. It also uses 33 tones, in this case spaced 9Hz apart (actually 8.7890625 Hz, exactly 1.5 x the baud rate at the highest speed), resulting in a signal bandwidth of 300Hz, including the keying sidebands (bandwidth assessed according to ITU-R SM.1138). The ITU Emission Designator is 300HF1B. The modulation is constant amplitude, phase coherent MFSK, using IFK+ coding with 32 frequency differences, yielding 32 unique codes. This means that each symbol carries enough information for all lower case letters to be expressed in just one symbol, which greatly enhances the speed.
Incremental MFSK Coding
IFK+ coding means that the character numbers from the alphabet table are added to the previous transmitted tone number, and ONE is added as well. The purpose of this added ONE is to force a continual rotation of the tones. This markedly improves tolerance of multi-path reception (reduces inter-symbol interference) and also assists in reducing the effect of carrier interference. When the resulting tone number exceeds 33, to keep the tones within range, 33 is subtracted from the tone number before transmission.
There is no 'idle' process in FSQ. Transmission starts with no padding, sends all the available characters, and stops when the buffer is empty. The receiver can lock to the signal following the first tone, as it measures the distance to the next tone. Thus the receiver detects and starts receiving the first character in under 200ms from the start of transmission.
Fast Fourier Transform Demodulation
At the receiver, the tones are spaced three FFT bins apart, which gives accurate rounding of the differences when the tone numbers are determined from the FFT bin index and divided by three. (Bin spacing is 2.9296875 Hz). This division reduces the effect of drift and Doppler by a factor of three as well. There are four alternative speeds (nominally 6, 4.5, 3 and 2 baud), although the tone spacing remains the same. (Default values are shown BOLD). Unusually for any digital mode, the receiver settings need not change when you change baud rate! Sensitivity is believed to be about -13 dB SNR at 6 baud, and -16 dB SNR at 3 baud. That's about 10dB better and several times faster than 12 WPM Morse, and slightly better than PSK31, MFSK16 and nearly as good as DominoEX11.
Automatic Preamble
Every transmission is automatically identified by the preamble callsign:, so the operator never needs to identify manually. At the receiver, whatever the sender types appears after the callsign preface.
In FSQCall Directed mode, a special 'end of transmission' character is added as the last transmitted character. FSQCall mode has slower squelch response, which aids reception through fades, and this special character is recognised and used to quickly close the squelch to prevent 'junk' from printing. We call this 'smart squelch'.
Character Coding
High typing speed for a given symbol rate is achieved through the use of a highly efficient character coding scheme using Varicodes. The FSQ alphabet has 29 characters that can be sent as a single symbol (all the lower case letters and frequently used punctuation) and a further 75 characters using two symbols, encompassing 104 ASCII characters in total.
Lower case should be used wherever possible, as not only are these characters twice as fast to send as upper case, they are generally easier to type, and the probability of errors in their reception is also halved.
Click the image to view the FSQ Alphabet and Varicode.
It's the same as used in WSQ.
Image Modes
FSQ images are transmitted as FM, using 400Hz deviation and a centre frequency of 1500Hz. Black is the lowest frequency, white (or maximum saturation colour) the highest. The pixel rate is 1200 pixels/sec. Three resolutions are offered: 640 x 480, 320 x 240, and 160 x 120 pixels, in a 4:3 format. The highest resolution is B&W only, the FSQ-FAX mode. The transmission times are 256, 192 and 48 seconds. Reception is achieved using a DSP phase detector and appropriate low pass filters. Interpolation is used before transmission, and after reception, to give consistent high quality 640x480 images. Any size landscape mode picture can be sent. Colour is sent as three sequential RGB lines. No framing pulses are transmitted before the picture, and no sync pulses are transmitted. The image transmission is synchronous.
All pictures have an FSQ mode preamble detailing the sender and the format. In Directed mode, reception is automatic at addressed stations.
