Search This Blog

Sunday, 14 July 2013

JT what - Ah, JT9!


A while ago I had a play with JT9 - its a cousin of the popular JT65. JT65 was designed for V/UHF comms and JT9 was designed for L/MF. Now JT65 has proved popular on the HF bands generally, and , for example on 20M, you would find JT65 with a dial frequency on USB of 14.076. Now, JT9 is typically found 2KHz above this, so on 20M this would need a dial frequency of 14.078.

The latest and greatest piece of software from the gang that develop the WSJT software, more specifically WSJT-X, have now included a bi-lingual feature! The software can receive both JT65 and JT9 at the same time!

To do this you need a radio capable of a wide RX - 4KHz required here for the full spectrum of both types of transmission. I have completely failed to find  way to do this with my FT-DX-3000, but have managed to get the FT-DX-5000 configured to do this.

I hoped to do this in PKT mode, but the width is fixed at a maximum of 2.4KHz in this mode, but in USB you can set the bandwidth to 4KHz (I struggled to see this full bandwidth in the waterfall until I remembered that I had a 3KHz roofing filter in line - doh!).

So, here is a screen shot from the latest WSJT-X:

including my first JT9 QSO with CT1FBK - thanks Miguel! The JT9 signals are to the right of the blue line at 2500Hz in the smaller window with the JT65 signals to the left.

Now, most (if not all) commercial SSB transceivers include an audio filter in the TX path, this means that the radio cannot generate the tones over the necessary spectrum for both JT65 and JT9 with a single dial frequency. To get round this the software includes CAT interfacing and you run the radio in split mode, using VFO A for RX and VFO B for TX. When you TX in JT9 the dial frequency on the TX VFO is altered and the appropriate tones generated.

Simply genius!

No comments:

Post a Comment