FT8

Interesting FT8 Videos

Joseph Taylor

FT8 Developer

Nobel Laureate

Have you caught the FT8 bug yet?? I have and I love this new digital mode from Joe Taylor, K1JT and Steve Franke, K9AN. FT8 (Franke-Taylor design, 8-FSK modulation) is designed for situations like multi-hop Es where signals are weak and fading, openings may be short, and you want fast completion of reliable, confirmable QSOs. And the best part about FT8 is that you can complete a QSO in <2 minutes!

According to J. Taylor, the important characteristics of FT8 are:

• >T/R sequence length: 15 s
• >Message length: 75 bits + 12-bit CRC
• >FEC code: LDPC(174,87)
• >Modulation: 8-FSK, keying rate = tone spacing = 5.86 Hz
• >Waveform: Continuous phase, constant envelope
• >Occupied bandwidth: 47 Hz
• >Synchronization: three 7x7 Costas arrays (start, middle, end of Tx)
• >Transmission duration: 79*2048/12000 = 13.48 s
• >Decoding threshold: -20 dB (perhaps -24 dB with a priori decoding, TBD)
• >Operational behavior: similar to HF usage of JT9, JT65
• >Multi-decoder: finds and decodes all FT8 signals in passband
• >Auto-sequencing after manual start of QSO

Compared to the so called slow modes (JT9, JT65, QRA64), FT8 is a few dB less sensitive but allows completion of QSOs four times faster. Bandwidth is greater than JT9, but about 1/4 of JT65A and less than 1/2 QRA64. Compared with the fast modes (JT9E-H), FT8 is significantly more sensitive, has much smaller bandwidth, uses the vertical waterfall, and offers multi-decoding over the full displayed passband. Features not yet implemented include signal subtraction, two-pass decoding, and use of a priori (already known) information as it accumulates during a QSO." (Source: Wikipedia)

Joe Taylor also released an update to his software program WSJT-X to support FT8. I absolutely love this program compared to the JT65-HF that I have been using for JT65. It's more flexable and has an automatic sequencer so you can start your QSO and sit back while the software does the rest!

It also has a nice waterfall screen too!

You can download the new WSJT-X at: https://wsjt.sourceforge.io/wsjtx.html

There are a number of operating frequencies for FT8 on the HF bands. They are:

Enjoy this new mode. Oh and I worked over 30 states in just 3 days. This is a quick way to reach WAS too! FT8 is now supported in LoTW.

JT65

Joseph Taylor

FT8 Developer

Nobel Laureate

JT65, developed and released in late 2003, is intended for extremely weak but slowly varying signals, such as those found on troposcatter or Earth-Moon-Earth (EME, or "moonbounce") paths. It can decode signals many decibels below the noise floor, and can often allow amateurs to successfully exchange contact information without signals being audible to the human ear. Like the other modes, multiple-frequency shift keying is employed; unlike the other modes, messages are transmitted as atomic units after being compressed and then encoded with a process known as forward error correction (or "FEC"). The FEC adds redundancy to the data, such that all of a message may be successfully recovered even if some bits are not received by the receiver. (The particular code used for JT65 is Reed-Solomon.) Because of this FEC process, messages are either decoded correctly or not decoded at all, with very high probability. After messages are encoded, they are transmitted using MFSK with 65 tones.

Operators have also begun using the JT65 mode for contacts on the HF bands, often using QRP (very low transmit power); while the mode was not originally intended for such use, its popularity has resulted in several new features being added to WSJT in order to facilitate HF operation. JT65-HF is shown in the image above.

(Source: Wikipedia)

There are a number of operating frequencies for JT65 on the HF bands. They are:

From the hflink.com website, they recommend the following guidelines for JT65 operation:

1. Operators should be careful of frequency selection, accurate clock, and calibration. Always listen and observe the waterfall spectrum of signals on the frequency before transmitting, and during activity.   

2. JT65A is a weak signal digital QSO mode. Always use very low power on HF to avoid QRM to other JT65 signals and other modes. 20Watts ERP is maximum for normal activity and DXing in the 40metre to 10metre bands.

3. Normal activity of JT65A is in the "weak signal" part of the ham bands, near the PSK, MFSK, and Olivia 500 frequencies. JT65A should not be used in parts of the ham bands where faster digital modes are in use. 

4. The long tone carrier duration of JT65 transmissions has potential to cause severe interference to other modes. 

5. Do not use JT65 in 10144kHz-10150kHz because JT65A is NOT COMPATIBLE with MFSK, FSK, HELL, OLIVIA, CONTESTIA, ALE400, or RTTY and can cause severe interference to fast time-sharing modes such as PACKET, PACTOR, ALE, PSKmail, and APRS.

PSK (Phase-Shit Keying)

Interesting PSK Videos

Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave).

Any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. This requires the receiver to be able to compare the phase of the received signal to a reference signal such a system is termed coherent (and referred to as CPSK).

Alternatively, instead of using the bit patterns to set the phase of the wave, it can instead be used to change it by a specified amount. The demodulator then determines the changes in the phase of the received signal rather than the phase itself. Since this scheme depends on the difference between successive phases, it is termed differential phase-shift keying (DPSK). DPSK can be significantly simpler to implement than ordinary PSK since there is no need for the demodulator to have a copy of the reference signal to determine the exact phase of the received signal (it is a non-coherent scheme). In exchange, it produces more erroneous demodulations. The exact requirements of the particular scenario under consideration determine which scheme is used.

Source: Wikipedia: http://en.wikipedia.org/wiki/Phase-shift_keying

One of the more popular software tools for working PSK is Ham Radio Deluxe and Digital Master 780. DM 780 makes it very easy to work PSK and to view multiple signals. Since PSK alls multiple QSO's to take place at once in the bandwidth of voice transmissions, PSK31 is a very efficient method for communications. Because the bandwidth used is very small, the amount of power needed for a transmission can also be small.

The image above is a screen capture of DM780 capturing a PSK31 QSO. The screen shows the typical PSK transmit and receive windows, but more importanlty, the "Waterfall" plot. The watefall plot is a very useful tool because it represents a graphical window that allows you visualize the station that are active and transmitting within a 31 kHz bandwidth. The stronger signals have the brighter colors, while the weaker signals will not be as bright. Using the waterfall graphic really is what makes PSK31 operation easy to tune and enjoyable to work.

All that is really needed to run PSK31 is an HF radio, a computer with a sound card, an interface that connects to the PC and the transceiver such as a RigBlaster or a homebrewed audio coupled solution and Ham Radio Deluxe.

Another neat feature built into DM-780 for PSK31 is the 'Super Browser'. A picture of the Super Browser is on the right. It allows you to see all on-going conversations and calls, and easily connect or join in by simply clicking the red test string of the station you wish to contact. It works by simply turning the waterfall up on it's side, and decoding each individual data stream...all at once! I find this very useful for quickly spotting a station that I might want to call CQ to.

There is a great tool available for looking for PSK contacts and that is from Hamspots.net. They offer a great tool that allows you to see PSK spots that have been found by other operators.

RTTY (Radioteletype)

Interesting RTTY Videos

What is RTTY?

Radioteletype (RTTY) is a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations, later superseded by personal computers (PCs) running software to emulate teleprinters, connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. The US Navy Department successfully tested printing telegraphy between an airplane and ground radio station in 1922. Later that year, the Radio Corporation of America successfully tested printing telegraphy via their Chatham, Massachusetts, radio station to the R.M.S. Majestic. Commercial RTTY systems were in active service between San Francisco and Honolulu as early as April 1932 and between San Francisco and New York City by 1934. The US military used radioteletype in the 1930s and expanded this usage during World War II. From the 1980s, teleprinters were replaced by computers running teleprinter emulation software.

An Amateur Radio radioteletype (RTTY) station consists of four distinct parts: A computer with a sound card, an modem interface such as the West Mountain Radio RigBlaster or the Tigertronics SignaLink, decoding software (See below), and an HF Radio. The sound card performs the functions of the modem and the PC performs the processing of the digital bits. Historically, a Teletype or teleprinter was an electromechanical or electronic device. The word "Teletype" was a trademark of the Teletype Corporation, so the terms "TTY", "RTTY","RATT" and "teleprinter" are usually used to describe a generic device without reference to a particular manufacturer.

RTTY uses the Baudot code. The Baudot code uses data bits to represent letters, numbers and punctuation, much like your computer does. Unlike your computer, which uses eight bits for each character, the Baudot code uses only five, plus a start bit and stop bit. Using fewer bits speeds up transmission and reduces the chance of errors. Unfortunately, five data bits allow for only 32 different codes, which cannot accommodate the 26 letters, 10 figures, space, a few punctuation marks and the required control codes, such as carriage return, new line, bell, etc. To overcome this limitation, RTTY also includes two states, the unshifted or letters state and the shifted ornumbers or figures state. The change from one state to the other takes place when the special control codes LETTERS and FIGURES are sent from the keyboard or received from the line. In the letters state, the RTTY system prints the letters and space while in the shifted state it prints the numerals and punctuation marks.

During transmission, the modem converts the digital signal transmitted to one or the other of a pair of audio frequency tones, traditionally 2295/2125 Hz (US) or 2125/1955 Hz (Europe). One of the tones corresponds to the mark condition and the other to the space condition. These audio tones, then, modulate an SSB transmitter to produce the final audio-frequency shift keying (AFSK) radio frequency signal. Some transmitters are capable of directfrequency-shift keying (FSK) as they can directly accept the digital signal and change their transmitting frequency according to the mark or space input state.

On reception, the FSK signal is converted to the original tones by mixing the FSK signal with a local oscillator called the BFO or beat frequency oscillator. These tones are fed to the demodulator part of the modem, which processes them through a series of filters and detectors to recreate the original digital signal. The FSK signals are audible on a communications radio receiver equipped with a BFO, and have a distinctive "beedle-eeeedle-eedle-eee" sound, usually starting and ending on one of the two tones ("idle on mark").

The most common test signal is a series of "RYRYRY" characters, as these form an alternating tone pattern exercising all bits and are easily-recognized.

For more information and a great tutorial on RTTY, I recommend reading IW5EDI's (Simone Mannini) great tutorial on RTTY.

Source: Wikipedia: http://en.wikipedia.org/wiki/Radioteletype

One of the more popular software tools for working RTTY is Ham Radio Deluxe and Digital Master 780. DM 780 makes it very easy to work RTTY. DM 780 gives you the ability to see multiple RTTY QSO's so you can quickly tune and call CQ or answer a CQ call.

The image on the right is a screen capture of DM780 capturing a RTTY QSO. The screen shows the typical RTTY transmit and receive windows, but more importanlty, the "Waterfall" plot. The watefall plot is a very useful tool because it represents a graphical window that allows you visualize the station that are active and transmitting. The stronger signals have brighter colors, while weaker signals will not be as bright. Using the waterfall graphic really is what makes RTTY1 operation easy to tune and enjoyable to work.

All that is really needed to run RTTY is an HF radio, a computer with a sound card, an interface that connects to the PC and the transceiver such as a RigBlaster or a homebrewed audio coupled solution and Ham Radio Deluxe.

A relatively new piece of software I found that runs RTTY (as well as PSK and MFSK) is Airlink Express from KR1ST. Airlink Express is a user friendly digital mode software package for the Amateur Radio Operator. The software is compatible with Microsoft Windows XP, Microsoft Windows Vista, and Microsoft Windows 7. With the release of Windows Vista and Windows 7, Microsoft introduced a new sound architecture. Airlink Express was developed to support this new sound architecture, yet it maintains complete backward compatibility with Windows XP. Unfortunately, Airlink Express has reached end of life.

The DSP engine used in Airlink Express is MMVari by Makoto Mori, JE3HHT. This engine is very flexible and decodes as well, if not better, than any other soundcard mode engine currently available. It is used by many other software products like Logger32 and the N1MM contest logger.

By far, one of the most popular RTTY programs around is MMTTY by JE3HHT, Makoto (Mako) Mori. Makoto is also the author of another very popular software called MMSSTV which is used to decode analog slow scan television pictures. MMTTY is very easy to use and it is FREE!

Tuning RTTY signals is not difficult. MMTTY makes it easy. MMTTY comes with a spectrum display (called FFT Display), an XY scope, and a waterfall display as shown below.

The spectrum display (FFT) is useful for initial tuning to get close to a signal. The XY Scope is then used for fine tuning.  The two yellow vertical bars represent Mark and Space frequencies. The final tuning goal is to line up the signal with these vertical bars. Once this is accomplished, the signal indicator on the MMTTY screen should go above the squelch threshold and you will begin to see readable text begin to scroll across the screen. It is that easy!.

Feld Hell

Interesting FELD HELL Videos

What is FELD HELL or HELLSCHREIBER?

Hellschreiber, or Hell, is a method of sending and receiving text using facsimile technology. It is unique in that the characters are not decoded, but "painted" or printed on a screen. There are several modes of Hellschreiber, the most popular being a single-tone version call Feld-Hell, an on-off keyed system with 122.5 dots/second, or about a 35 WPM text rate. FH has a narrow bandwidth of about 75 Hz. Feld-Hell also has the advantage of having a low duty cycle meaning your transmitter will run much cooler with this mode.

How does Hellschreiber work (from Wikipedia)

Hellschreiber sends a page of text as a series of vertical columns. Each column is broken down vertically into a series of pixels, normally using a 7 by 7 pixel grid to represent characters. The data for a line is then sent as a series of on-off signals to the receiver, using a variety of formats depending on the medium, but normally at a rate of 112.5 baud.

At the receiver end, a paper tape is fed at a constant speed over a roller. Above the roller was a spinning cylinder with small bumps on the surface. The received signal was amplified and sent to a magnetic actuator that pulled the cylinder down onto the roller, hammering a dot into the surface of the paper. All implementations of Hellschreiber print all received columns twice, one below the other (but they are not transmitted twice). This is to compensate for slight timing errors that are often present in the equipment, and causes the text to slant. The received text can look like two identical texts coming out one below the other, or a line of text coming out in the middle, with chopped-off lines above and below. In either case, at least one whole letter can be read at all times.

The original Hellschreiber machine was a mechanical device, so therefore it was possible to send "half-pixels". The right ends of the loops in B, for instance, could be shifted a little, so as to improve the readability. Any on-signal could in any case last no shorter than 8 ms, however, both because of having to restrict the occupied bandwidth on the radio, but also for reasons having to do with the mechanical makeup of the receiving machinery.

Improvements that came as a result of software implementation:

=> Depicting the received signal as shades of gray instead of monochrome, thereby making it much easier to read weak signals.

=> Changing to a different font. Here is one mode that is truly international and independent of character sets: any thing that can be depicted as markings within a 7 pixels high grid, can be transmitted over the air.

Spectrogram of a Feld-Hell transmission centered on 7072.0KHz.

Suggested further reading: How the Hellschreiber works

CONTESTIA

Interesting Contestia Videos

What is CONTESTIA?

Contestia is a digital mode directly derived from Olivia that is not quite as robust - but more of a compromise between speed and performance. It was developed by Nick Fedoseev, UT2UZ, in 2005. It sounds almost identical to Olivia, can be configured in as many ways, but has essentially twice the speed.

Excerpts from the www.oliviamode.com/Contestia.htm site:

Contestia has 40 formats just like Olivia - some of which are considered standard and they all have different characteristics.  The formats vary in bandwidth (125,250,500,1000, and 2000hz) and number of tones used (2,4,8,16,32,64,128, or 256).

The standard Contestia formats (bandwidth/tones) are 125/4, 250/8, 500/16, 1000/32, and 2000/64.

The most commonly used formats right now seem to be 250/8, 500/16, and 1000/32. 

How well does Contestia perform?

Contestia performs very well under weak signal conditions.  It handles QRM, QRN, and QSB very well also. It decodes below the noise level but Olivia still outperforms it in this area by about 1.5 - 3db depending on configuration.

It is twice as fast as Olivia per configuration.  It is an excellent weak signal, ragchew, QRP, and DX digital mode.  When ragchewing under fair or better conditions it can be more preferable to many hams than Olivia because of the faster speed.  For  contests it might also be a good mode IF the even faster configurations such as 1000/8 or 500/4 are used.

Contestia get it's increased speed by using a smaller symbol block size (32) than Olivia (64) and by a using 6bit decimal character set rather than 7bit ASCII set that Olivia does. 

Therefore, it has a reduced character set and does not print out in both upper and lower case (like RTTY).  Some traffic nets might not want to use this mode because it does not support upper and lower case characters and extended characters found in many documents and messages.  For normal digital chats and ham communications that does not pose any problem.

Here are example waterfalls and audios of various Contestia modes (Obtained from www.sigidwiki.com/wiki/Contestia)

4/125

4/250

4/500

8/250

8/500

16/500

MFSK (Multiple Frequency-Shift Keying)

Interesting MFSK Videos

What is MFSK?

Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal waveforms. M, the size of the alphabet, is usually a power of two so that each symbol represents log2M bits.

MFSK-8 and MFSK-16 are two well-known amateur radio modes. MFSK16 and MFSK8 were developed by Murray ZL1BPU and Nino IZ8BLY in 1999. MFSK-8 uses a set of 32 tones with the equal distance of 7.81 Hz, MFSK-16 a set of 16 tones with the equal distance of 15.625 Hz. The baud rate of MFSK-8 is 7.81 Bd and that of MFSK-16 is 15.625 Bd.

Another form of MFSK is Olivia. Olivia MFSK is an amateur radioteletype protocol, using multiple frequency-shift keying (MFSK) and designed to work in difficult (low signal-to-noise ratio plus multipath propagation) conditions on shortwave bands. The signal can be accurately received even if the surrounding noise is 10 dB stronger. It is commonly used by amateur radio operators to reliably transmit ASCII characters over noisy channels using the high frequency (3–30 MHz) spectrum. The effective data rate of the Olivia MFSK protocol is 150 characters/minute.

Olivia modes are commonly referred to as Olivia X / Y (or, alternatively, Olivia Y / X ), where X refers to the number of different audio tones transmitted and Y refers to the bandwidth in hertz over which these signals are spread. Examples of common Olivia modes are 16/500, 32/1000 and 8/250.

A visual of what a MFSK signal looks like:

What does MFSK sound like?

From the SIGIDWIKI.COM web site, here is what some MFSK mode samples sound like:

MFSK 4

MFSK 8

MFSK 11

MFSK 16

MFSK 22

MFSK 32

MFSK 64

MFSK 128