Digital modes are making their mark on VHF and above through their ability to process very weak signals (tropo and EME), to make use of very short meteor bursts or cope with multi-path signals (Aurora). Examples of performance are as follows:
Meteor Scatter: The FSK441 mode provided with WSJT is allowing routine contacts on two meters in the range 800 km to 1800 km with 100 watts and a single yagi.
EME: The JT44 mode provided with WSJT is allowing EME contacts with one yagi and 100 watts that previously required four yagis.
Aurora: Hellshreiber at 1/8th speed is allowing Auroral contacts that cannot be heard.
WSJT stands for Weak Signal communications by K1JT, Joe Taylor. Its FSK441 mode has been specifically designed for meteor scatter. It can use random meteors that are available throughout the year. It works best in the range 800 km to 1800 km where contacts on 144MHz can be completed with 100 watts and a single yagi in typically 20 minutes.
Download Program at: http://pulsar.princeton.edu/~joe/K1JT/
Operating Procedures in VK: FSK441-Proc
Performance: WSJT – FSK441
WSJT’s JT44 mode is designed for EME and works well on tropo scatter. A major advantage is that it will pick up and correctly decode signals if they are within 600 Hz of correct tuning - thus it copes well with Doppler shift from the moon on EME and does not require accurate tuning to find a weak tropo signal.
Experience on 2m EME (VK2FLR) indicates that one can achieve contacts on a single yagi that require 4 yagis on CW. A number of VK stations have worked the so-called super stations with a single 10-element yagi and 100 watts.
Download Program at: http://pulsar.princeton.edu/~joe/K1JT/
Operating Procedures in VK: JT44-Proc
These modes operate at higher speed than JT44 but do not have the same weak signal performance.
While there is a wide range of programs available for PSK31 a good program that covers PSK31, MFSK 8 and MFSK 16 has been developed by an Italian amateur Nino Porcino, IZ8BLY.
Down load IZ8BLY Program at: http://home.wanadoo.nl/nl9222/
When you arrive at this site go to Digital Modes and look for IZ8BLY Stream.
HSCW is aimed at meteor scatter. While it can be received on a tape recorder and slowed down, a Croatian University Student, Tihomir Heidelburg 9A4GL, has produced a computer program called WinMSDSP that automatically transmits the High speed CW and slows down the received signal for reception by ear. Proponents consider the performance of HSCW to be comparable with or better than FSK441.
Download Program at: http://www.qsl.net/w8wn/hscw/msdsp.html
The downloaded program will run for 15 minutes – enough to see if you like it. If you wish to remove the 15-minute limit there is a $20 US fee.
In its faster forms (5xHell and 9xHell) Hellshreiber works well on meteor scatter on six metres. However, it is too slow for random meteors on two meters and has been superseded by FSK441. In its slower forms (1xHell to 1/8th Hell) it works well on tropo scatter but cannot compete with JT44. Despite this it is a real time mode that allows one to see the effects of propagation and is well worth the experience.
The one area in which Hellshreiber holds its own is auroral propagation. The reason for this is that it in its slower forms (1xHell to 1/8th Hell) it copes well with both the multi-path propagation and frequency spreading caused by auroral propagation. Experience has shown that it can produce a readable signal from auroral propagation in circumstances where the signal cannot be heard by ear.
Download program at: http://home.wanadoo.nl/nl9222/,
then go to Visual modes and look for IZ8BLY HELL V3.8
VFSKCW stands for Visual Frequency Shift Keyed CW. VFSKCW was developed by Steve Olney VK2ZTO for very low frequency use but has proved useful for VHF. The program provides for TX only and it must be received on a waterfall program such as Spectrogram or Spectran. VFSKCW signals can be seen at levels undetectable to JT44, however, the slow speed means that QSB on tropo scatter inhibits its performance in completing QSOs.
Spectrogram and Spectran both have waterfall displays that show the audio frequency spectrum and can detect signals in very narrow bandwidths even though they are looking across a much wider bandwidth. Essentially this gives one the advantage of a very narrow receiver (say less than 1Hz bandwidth) but with the ability to watch for a signal across the full SSB passband. In addition to their use in receiving VFSKCW they are particularly useful in looking for very weak signals from beacons.
Spectrogram works to a resolution (equivalent to receiver noise bandwidth) of 0.3 Hz whereas Spectran will work down to 0.02 Hz. In practice there seems little benefit in going lower than 0.3 Hz at VHF and most users seem to prefer Spectrogram.
Download Program at: http://home.wanadoo.nl/nl9222/
next go to Visual Modes and then:
For VFSKCW look for VFSKCW 05
For Spectrogram look for Spectrogram 517
For Spectran look for Spectran 1-107
All of these programs are free, however there are later versions of Spectrogram available for a registration fee of $25 US that allow one to independently set the resolution and the audio range over which it scans. While this feature is not essential it is useful if you use VFSKCW frequently or often look for very weak beacons.
Download pay version at: http://www.visualizationsoftware.com/gram.html
The requirements to run all of the above modes are:
An SSB transceiver and antenna
A PC with around 100 MHz Pentium or better and Windows 95 or better (note that faster Hellshrieber modes (5xHell and above) can require a faster machine)
An interface such as those widely used for PSK31: for example see article by Alan Gibbs VK6PG in Amateur Radio, March 2000, page 36.
Software that can be downloaded from the Web as above.
For the full bandplan refer to the following WIA site:
http://www.wia.org.au/bandplans/
The key elements for terrestrial use of the digital modes are:
144.220 or 144.320: Narrow modes of less than 100 Hz bandwidth such as VFSKCW and PSK31, primarily aimed at tropo scatter.
144.225 or 144.325: Modes of greater than 100 Hz bandwidth, eg JT44, MFSK and Hellshreiber (normal speed or low).
144.230 or 144.330: Meteor scatter modes, FSK441 and fast Hell
The first frequency is the focus frequency and the second is an alternate. A similar pattern applies on all higher bands eg 432.225 for JT44.
At this stage there is no specific band plan for JT44 EME activity, however activity seems to be concentrated between 144.140 and 144.180.