Try WSJT for weak signal contacts

I've done quite a few things in amateur radio, but one of the things I absolutely enjoy is DXing. I also enjoy pulling out the weak ones from a pileup or working weak signals in general.  But on traditional modes it can be a bit frustrating, especially on fickle bands like 6 meters. Enter the WSJT modes.

First things first, if you're looking to have a nice long chat with a friend, look elsewhere. The mode is not for this kind of stuff. Rather, you are getting a basic signal report and grid square exchange. You may exchange a short text message but only 13 characters maximum (move over, Twitter!) Secondly, you do not need to or want to run high power in most cases. This is great news for those who like to operate QRP. 

About the mode, history and origins

The mode was developed by noted Astrophysicist and Nobel Prize Laureate, Joe Taylor, K1JT. Joe's extensive resumé includes discovering pulsars using the NRAO radio telescopes in West Virginia. Prior to that he had worked with Jocelyn Bell, who had discovered the first pulsars. He first started out in amateur radio as a teenager and this fueled his interest in radio astronomy. One can clearly see how his love for "weak signal work" goes well beyond amateur radio or the solar system, for that matter. 

The mode can allow one to work signals that are not audible to the human ear, many dB below the noise floor. It does this by repetition and slow transmission. This is why you can't rag chew with it, but it is great for working DX and new grid squares.

It is used extensively for moonbounce (EME) where signals are reflected off the moon. However EME operators often use 500+ watts to compensate for path loss. Prior to the WSJT modes you'd see EME enthusiasts with stacks and stacks upon stacks of yagis pointing at the sky, and 1.5kw on 2 meters. They'd run CW and sometimes SSB. They'd send Ts to verify the signal and make skeds on HF or internet. While much of that is still done today, it is now possible to point at the moon and CQ with just one or two yagis and a few hundred watts. It is also possible to make contacts on supposedly dead bands like 6 meters. It is also possible to work DX on HF with small wire antennas.

Software setup

So how do you get cooking with JT modes anyway? We'll do a simple JT65 setup here. This is a very basic guide to get you started. 

You'll need:
  • SSB capable radio and your antenna
  • Sound card interface - external sound card interface like a SignaLink or some newer radios (like the Elecraft K3S or IC7300) have it built in and accessible via the USB port.
  • PC or Mac with WSJT software (JT65-HF or WSJT-X usually)
  • Internet synchronized PC clock (very important).
  • Patience and quick reaction time.

Once you get all of those together, you can then configure the software. I'll keep it simple as I use JT65-HF. WSJT-X is supposedly better but I've had better luck with JT65-HF. However, JT65-HF hasn't really been maintained since about 2013. But it still works very well. 

I use Windows for my shack PC but you can use any OS including Linux and Mac OS X. WSJT software and the protocol are all open source so you can compile it for any OS. 

A note about time sync: JT65 is a timed mode, meaning that everything fires off at certain times. Therefore your PC clock must be in sync. You can use software like Dimension 4 or Meinberg to do that. Unfortunately the built in time sync feature in Windows doesn't seem sufficient. You may need administrator privileges on your PC to do this.

Once you get the time sync portion straightened out and you've installed JT65-HF, you can set it up easily like this. Most important is the audio device (USB sound card) and your callsign and grid:

Make sure you have PTT and optionally, rig control (for band changes. It supports OmniRig and Ham Radio Deluxe, or serial port control. Note: if you have a SignaLink it uses VOX so there's no need to configure PTT in that case. But some sound card interfaces require it.

This is the main window:

You generally set your radio to USB (upper sideband) mode. Set power to low power (maximum 25-35 watts, many use 5 watts or less). Turn off speech compressor/processor. You can use the mode anywhere on the digital sub-bands but most people use the JT65 window. Here are the frequencies. Note that these are the dial frequencies in kHz you set your radio to:

  • 160m - 1836-1838
  • 80m - 3576
  • 40m - 7076
  • 20m - 14076
  • 30m - 10138
  • 20m - 14076
  • 17m - 18102
  • 15m - 21076
  • 12m - 24917
  • 10m - 28076
  • 6m - 50276
My favorite hangouts are 6m and 40m. I have worked many grids on 6m using JT65.

How a typical JT65 QSO works:

0001z  At the top of the minute a station will transmit "CQ <callsign> <grid square>" 
0002z  The responding operator will send her callsign and 4 digit grid square.
0003z: The CQing operator (who she has now answered) will send a signal report. 
0004z: The responding operator will send a "R" (roger) and her signal report
0005z: The CQing operator will send "RRR"
0006z: The responding operator will send "RRR"
0007z: The CQing operator will send "73"
0008z: The responding operator will send "73"

Yes, that is 8 whole minutes!

QSO is logged using the "log QSO" button. The signal report is in dB and is generated automatically. You can put in your transmitter power if desired. 

Most people take a shortcut and can cut that down to 6 minutes by omitting the RRRs from minute 5 and 6 and simply send 73s. 

So it would be something like this:

0001z - CQ KA1ULN FN41
0002z - KA1ULN N2RJ FN21
0003z - N2RJ KA1ULN -08
0004z - KA1ULN N2RJ -09
0005z - N2RJ KA1ULN 73
0006z - KA1ULN N2RJ 73

I hit "log QSO" button and I'm done. 

Note that each transmission lasts 47 seconds and you have to make your decision in 13 seconds what to transmit next. It's sort of like playing 5 minute lightning chess where you press the clock after each move, except that each move is timed. You will see the waterfall stop and a red line where you're supposed to transmit. You'll also see the decoded messages in the window. Messages sent to you are red. General CQs are green. If you have your headphones on you'll hear when the other side's transmission.

I wish there was a way to substitute 88 or 33 in the protocol but from what I gather, 73 is hard coded in the protocol. 

By the way, each transmission is basically brick on key for 47 seconds! This is one big reason why most people do not run high power as their rigs would overheat and their finals would burn up. 

But I was this close to working that rare grid on 6!

JT65-HF generates a log file in ADIF format that you can import into your log software. The log file is located at C:\Users\<your_username>\Appdata\JT65-HF\.  I prefer to consolidate my logs into Ham Radio Deluxe so this works perfectly for me. Then I can upload to LoTW and other systems. 

A word about QSLing

The final courtesy of the QSO is the QSL, and it isn't finished until the paperwork is done! The good news is that most JT65 users use LoTW.  Many also use eQSL and logbook. This saves the time and expense of sending for QSL cards. With LoTW you can apply toward VUCC, DXCC, WAS and other awards quite easily. With eQSL you can apply for their own eAwards or CQ magazine awards such as WAZ or WPX. QRZ has their own awards system as well. 

And that's it! Now you can make a simple JT65 QSO and work the rare grid squares with low power and a compromise antenna. 

Until next time! CUAGN on my waterfall.

Ria, N2RJ

PS - I'm new here and will be writing from time to time. Niece has graciously allowed me to contribute to her blog, so we can have a source of knowledge for YLs (and anyone, really) to enhance their experience in the hobby. My info is on if you'd like to contact me. 

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