Presentationer och föredrag, WSJT-X och digitala trafiksätt..

Från och med 2017 har jag beslutat mig för att öppet erbjuda olika föreläsningar, presentationer eller kurser gällande digitala trafiksätt. Målgruppen är främst amatörradioföreningar eller klubbar och sker helt ideellt utan kostnad.

Som start erbjuder jag förevisningar, kurser eller presentationer av WSJT-X för JT65 och JT9. Se sidan “Föredrag” för mer information. 🙂

73 de SM7VRZ

Release of WSJT-X V1.7.0

wsjtx170Just a few minutes ago the new release of WSJT-X, V1.7.0, was released by K1JT, Joe on the WSJT-homepage. The new version contains a lot of new functions an modes but the most useful update for us using the software on the HF-bands is the new Franke-Taylor decoder. This decoder replaces the Koetter-Vardy decoder used in previous WSJT-X versions. The KVASD is no longer necessary to install. In addition to this there is now multi-pass decoding which is very helpful in the crowded JT65-frequencies. The function uses two decoding passes instead of one, increasing the possibility to decode overlapping transmissions or weaker stations buried in a crowded passband.

Download the installation package for windows now from the WSJT-X website or click here to start the download.

Installation packages for Mac and Linux is also available on the WSJT-X website.

The Swedish translation of the user guide is not yet ready for release but will be finished in the first quarter of 2017.
Have fun! 😀

73 de SM7VRZ

Translations and summer plans..

It seems like there’s some time between the updates in the blog right now and I do have my reasons for it. A hectic work situation with a number of new projects starting and an ability not to leave the thoughts about the project situations when you get home have rendered me some what exhausted. However I’ve done some progress with my latest undertaking, the translation of the WSJT-X user manual into Swedish. svmanJust this morning I’ve completed the basic translation work and I now have to proof read the entire manual to check for consistency and spelling errors. After this, then additional content for WSJT-X V 1.7.0 has to be inserted.

The manual however is more or less a complete translation for the V 1.6.0 but as it has elements of the coming version in the texts it may be some what confusing to read in certain sections. There are also elements in the translated material that seems hard to change and are probably related either to the ASCIIdoc markup language or in the maner that the documentation is built. For example I can’t find out were to change the text “Table of Contents” in the left margin into Swedish as this is the only text that can’t be changed in the entire document, unless you change it in the compiled html-file. 🙂

Well, I guess I just ned to do some more digging to solve it I guess. 🙂

Thank’s to some work related circumstances I might get the chance to do some portable work on the Swedish West coast this summer. Even though it might be more work than play, I will try to find some time to make som QSO:s on digital and voice with my potable kit. The QTH is in the archipelago outside Gothenburg and I will probably be there for at least two weeks. Lets hope for the best! 🙂

73 de SM7VRZ

New year, new projects..

I´ve just realized that it´s been a couple of months since I updated the blog and it almost seems a bit empty when there are no updates made to it. Honestly I´ve not really had the time or the inspiration for it the last months as my work and family life have been taking up the most of the time. Even the HAM-radio activities have been on the low side. Since it´s a new year now (2016 already!!) I´m looking in to what kind of new projects I might want to take on this year.

As you may already know I´m a big fan of the JT9/65 modes on HF and my activities are, except for the SJ7SOP activity, almost only digimode in HAM radio. This interest in JT made me sign up to the WSJT development e-mail reflector to get more insight in the development of the WSJT-X software. Also, I got the opportunity to try a number of development versions of the software through the WSJT-X user group on Facebook. Thanks to the helpful and kind work of Udo (DO1IP) who made the devel-versions available for testing in the limited user group, I was able to follow the development of the WSJT-X software and also witness the amazing progress that have been made with the JT65 decoder.

text_to_speech_app_iconI decided to give something back to the WSJT project and since my skills in programming is quite limited I´ve instead looked at the possibility to make a translation of the WSJT-X manual in to Swedish. The initiative seemed to be appreciated among the developers why I´ve started to learning the Asciidoc markup language and how to build the user manual. I´m quite excited about this undertaking which will not only put my translation skills to the test, but also gives me an opportunity to learn a new way of documenting.

A new release candidate is not far away for the WSJT-X software and the translation work will probably start when It´s released. 🙂

Another interesting thing that just recently started up here in Sweden is the Svenska Sjöar or Swedish Lakes Competition, SMSS, (homepage only in Swedish) which is a competition involving making QSO:s from as many Swedish lakes as possible. This is a good way to activate HAMs, showing the fun of portable operation, running QRP and of coarse enjoying the beautiful Swedish nature. Some of the club members in my local club, SK7JC, has decided to join the competition and is about to arrange a club meeting to exchange experiences with QRP and portable operation. I will certainly also be a part of it, however I would like the temperature to be at least on the + side before I make a trip outside. 😀

Meanwhile, waiting for the mercury to crawl upp, I´ll make some plans for spring activation of the SMSS competition. 🙂

73 de SM7VRZ

Weak signal communication, JT65 and JT9…

I promised earlier that I would do a short presentation of the JT65 and JT9 modes. Well, here it is.

 

 Light technical presentation

JT65

JT65 was created by K1JT, Joseph Taylor, a radio astronomer and also a Nobel prize winner in 1993, mainly for EME (Earth Moon Earth) communication or moon bounce at VHF frequencies and up.  Although meant for EME, it grew popular among HF operators and today it has many users on the shortwave bands. The fact that it is a weak signal mode makes it also ideal for QRP operation.

The mode itself, on air, sounds like a melody being played. A transmission is made using AFSK (Audio Frequency Shift Keying) modulation and consists of 65 different tones in which one, the lowest, is a synchronization tone. A transmission occupies approximately 177 Hz of bandwidth in the SSB passband but the actual efficient bandwidth used by a transmission is actually much smaller than that. I will return to this later on.

jt65waterfall

Fig. 1 JT65 signal in a waterfall view

Figure 1 above shows a JT65 signal viewed as a “waterfall” image. On the left the sync tone can be seen as the clear line and to the right of the sync tone the 64 data information tones are visible as white dots.

The mode is time controlled, using even and odd minutes for transmission and receiving thus showing output to the operator once a minute. This makes operation very strict and not as free as with other digital modes on HF. The actual transmission or receiving period takes 48 seconds. During these seconds a pattern of tones is transmitted which correspond to the message generated by the software. After the 48 sec the decoder at the receiving end starts processing the received tones . The processing takes a few seconds, depending of the computer used, and the output is shown to the operator as text messages. The operator then has about 10 seconds to choose an action before a new reception interval begins or a transmission starts. A typical QSO takes about seven minutes. For just monitoring the traffic a new receiving interval begins every beginning of a new minute.

waterfall1

Fig 2. A waterfall image of monitoring JT65. Notice the stations almost exact timing in starting the transmissions.

As you can see the JT mode is dependent of correct timing. The software uses the computer clock for keeping the time synchronized with an accuracy of seconds. A drift as little as two seconds makes your transmitted signal undecodable to other operators and the received signals useless. As the common home computer normally isn’t that accurate in timing the use of an NTP client software is recommended and sometimes even necessary.

In figure 2 we can see an example of a waterfall view of a number of J65 transmissions. The waterfall view is divided in to minute “rows” by red horizontal lines were each red line represents the start of a new minute. All transmissions starts after the red lines with a nearly exact timing.

As it is a weak signal mode the decoder is capable of decoding signals with a very weak signal levels. The decoder can work with signals as low as -22 dB SNR (Signal to Noise Ratio) nearly without any error and down to -24 dB with about 50% decoding error. The capability for weak signal decoding is partly made possible thanks to the use of a forward error correcting technology (FEC) called Reed Solomon. The code is commonly used in CD-ROM and Hard Drives for producing extremely low error rates in data recovery. But it isn’t only the algorithms of the decoder that makes the magic. During the 48 second transmission the message is transmitted over and over again. Up to 80% of the transmission can be lost still producing a correct decoded message. This adds to the strength of the protocol.

Other than this there is the fact that the transmitted signal Is extremely narrow in bandwidth. As I mentioned above, the JT65 mode uses 177Hz in signal bandwidth. This is the bandwidth that the transmission needs “free” for its use. In the actual transmission each tone uses only a small portion of the bandwidth almost making it as narrow as a CW transmission.

This is also a strength of this mode as it makes the use of high power unnecessary. You can work long distances with QRP equipment.

JT9

As with JT65, it was created by K1JT as development of JT65 for use on the LF/MF and HF bands. The JT9 mode are in many ways similar to JT65 as the share the same basic concept. They are both using the 48 second transmission period,  decoder and time sensitivity but there are some differences.

jt9

 Fig. 3 A JT9 signal in a waterfall image

 The bandwidth of JT9 is much narrower using only 15.6Hz of the SSB passband with a nine tone AFSK transmission. One tone is for synchronization while the eight remaining is for data.  This allows more JT9 transmissions to occupy the same bandwidth as a single JT65 transmission. The decoder is capable of decoding signals as low as -22 dB SNR nearly without any error and down to -26 dB with about 50% decoding error. This adds some 2dB compared to JT65.

Other than this the two modes is just the same to the operator and just as JT65, JT9 is perfect for QRP use.

If you want to go deeper into the protocols of JT65 the creator have made a document describing the mode more in detail. The PDF document can be found here.

73

//Anders

Sharing the knowledge..

A few months ago I was contacted by the secretary of our local Ham Radio club, SK7JC, and asked if I could arrange a presentation of Digital modes on HF for the regional meeting for the Swedish national Amature radio accosiation in Karlshamn. The club had been appointed to host the meeting and was looking for activities to fill the meeting schedule.  I was thrilled and honored by the fact that they contacted me and I accepted the task and started working on a scope for the presentation.

I finally decided to have a light approach to the topic and only present the BPSK and JT modes i a light technical description, along with hardware and software demands and some useful tips and tools. To top it of, I will do a practical demonstration of a JT65/9 session to show the fun and fascination of the two modes. With this I will also demonstrate the usefulness of QRP operation with digital modes as I will use my FT-817ND  and Signalink USB interface in the demonstration.

DSC_0417

 

I’ve been working on the presentation, slides and notes a lot and I now feel like I’ve achieved a full working presentation. The Presentation will be published here on the blog the 15:th of november for those interested in seeing it. Note that It’s in Swedish! 🙂

73

//Anders