JT65 on HF
by George Szymanski, DU1GM
You may have heard of the digital mode JT65 which was developed by Joe, K1JT. He wrote a program which can generate and decode the various tones required for this and other digital modes. WS comes from Weak Signal and this mode is designed to dig out signals which you can hardly even hear and sometimes you can't hear at all. Your computer can display such a signal as a series of lines and dots and can decode it too! The mode was originally developed for EME working, or Moon Bounce, as signals reflected from the moon are usually extremely weak. You may have read Gil's article about his experiences using this mode on 50MHz EME. His interesting article can be read here...
There have also been a few DXPeditions locally which have made contacts on 6m and 2m using JT65 and Moon Bounce. Nowadays, this mode is gaining a large following on the HF bands, and this is the topic of this article.
I thought I would try the mode considering that my antenna is very poor due to severe space limitations. I can only use a vertical and the grounding is not too good. I can usually make contacts on the HF bands but signals are not very strong. JT65 offers the possibility of increasing the range of contacts without having to move to another QTH!
The program can be downloaded from :-
and the user guide (very important) can be downloaded from :-
Once the WSJT program is downloaded, you should run the setup and change the default callsign to your own as well as add your locator. In the Manila area this would be PK04. The program will also require that you setup the rx and tx to and from whichever soundcard you are using, otherwise you will not be able to receive or transmit.
Of course, you will need to use an interface between your computer and the transceiver. A simple unit with audio isolation will suffice and you can use VOX to activate the transceiver. This is the system I use at the present time . A good interface project was described by Joe DU1ANV, and can be read here :-
The WSJT mode most used on HF is JT65a, and this is selectable from the main screen menu. There are other modes selectable there but these are outside the scope of this article.
Once you have the program running and connected to your rig, what will you see? First of all there is a main screen which is shown here...
Information about the moon is displayed as this program was originally designed for Moon Bounce! It can be disregarded for the moment unless you want to go out and see it for yourself...
You can see a QSO in progress between myself and JA1KAU, which was completed in 4 minutes. You can see JA1KAU calling CQ on the first line and he has included his locator, PM64, which puts him in the Tokyo area. I responded with JA1KAU DU1GM PK04, this is not shown on the rx screen. He then responded with the two calls and locator to which I sent back JA1KAU DU1GM -15. The -15 refers to his signal strength and is the standard method of reporting on HF. Signals can be decoded as low as -26dB and the signal would not be audible in the speaker at that point. He obviously received my signals report as he responded with two calls and R-12. The R means he has received all information and the 12 was my signal report. I then sent back two calls and RRR and the QSO was complete. He came back with 73 to round things off.
Shown below is a screen shot of one receiving period...
The JT65a signal comprises of two sections. The leftmost line is the sync, and the dots to the right are tone signals comprising the information being sent. What does it sound like? Well, you will need to try it out for yourself and listen on the appropriate frequencies. Alternatively you can look at this link which has a number of digital mode sound bites including JT65a, http://www.bartg.org.uk/modesamples.asp
JT65A signal is normally about +1.3kHz to +1.5kHz
higher than the VFO frequency.
More information can be seen here.... http://hflink.com/jt65/
If the instruction manual is too much to absorb at one sitting, then look at this page which has a Bozo's guide to JT65a :-
There are a number of JT65 chat pages on the internet which will help you determine where your signals are reaching and you will be able to talk to like minded people and set up skeds. You can also set up your system to act as a "Reverse Beacon" so that call signs you receive in JT65a are shown on the chat page. This is very useful both for yourself to see where you are being received and at what signal strength as well as for others to know they are being received here.
http://jt65.w6cqz.org/main0.php is one well populated chat page and is the one I use most. There are stations on from all over the world as well as Reverse Beacon reports. If you want to operate as a Reverse Beacon you need to download a small program and put it in your WSJT folder then execute it when WSJT is running. This program can be downloaded from http://jt65.w6cqz.org/down/rbc.exe
I hope this short article has given you a taste of what is possible with this new mode. there are only a few stations in DU QRV on this mode at the moment, DU1GM, DU1MGA and DU1IVT, so we need more operators to make DU workable worldwide on this exciting digital mode.
Since posting this article I have worked many countries on JT65a. My power limit is 25W, largely constrained by the QRP tuner as well as consideration for the life of my 765PRO final transistors. If you are using this mode you should remember that you will be transmitting for 48 seconds what amounts to a steady carrier albeit consisting of varying tones, so your amplifier will get warm. My antenna is a simple vertical antenna, around 7m tall consisting of a fiberglass telescopic whip with a wire inside. The wire is fed directly to the tuner. There is a ground system which comprises a length of wire which goes down to ground level and finally connects to the steel water pipe.
DXCC Entities worked so far.....
|DA-DL||Fed. Rep. of Germany|
|K,W,N, AA-AK||United States of America|
|TOTAL: 29 DXCC entities||Best DX was PY8ELO, at 18,800km|
© Philippine Amateur Radio Association, Inc. 2009