Saturday, 25 June 2016

Icom IC-7300, WSJT, USB send, FSK and meteor scatter modes

I have had a change of heart since I wrote this. See also another posting with almost the same name here just a few days later:

Now this is going to be pretty nerdy for the meteor scatter community, but I think it is worth saying for us sky nuts.

As mentioned here before, the IC-7300 has a 13-pin DIN type accessory socket on the back where you can input PTT and audio in the classic manner. Using that socket you can send WSJT-type modes, and loads of others, connecting to your PC by a sound card and using a chip and RTS data to trip the PTT.

That will work, but some of us think that as the rig has a USB cable and the capacity to accept digital audio that is a better way to go. Indeed, working the PTT by hard wiring seems almost from the dark ages compared to CAT or CIV interfaces. The main advantage to using the USB lead is that software can set your transmitting frequency, mode and so forth, all at the same time.

Grand so, but there are still a lot of us using software such as WSJT10 for meteor scatter. The key modes we use, such as JT6M, FSK441 etc are not available yet on the WSJT-X suite. The drawback to this is that, unlike WSJT-X which integrates frequency and mode setting with PTT and audio, WSJT10 is built on the assumption that we will set our own frequency and use RTS (or DTR) signals to work the PTT either via a parallel cable or nowadays often via a parallel/ series converter chip and a USB cable. In other words, the WSJT10 concept is based on us using the accessory socket.

The 7300 will not accept the PTT commands from the WSJT10 software, and the WSJT-X suite does not include the modes we need. Or not quite. Unlike the IC-7100, the IC-7300 does include a "USB SEND" setting which appears to solve the problem.
There it is, under MENU, SET, CONNECTORS. Click that and the USB cable will accept either a DTR or RTS PTT signal from the WSJT10 software.


Not really.

The IC-7300 manual states "When you operate RTTY or CW through your PC’s USB port and your IC-7300, you may not be able to send “SEND” or “Keying” signals until a few seconds after you connect the USB cable."

For me, that means 5 seconds delay every time the WSJT software activates the PTT. NOT just 5 seconds delay the first time I use the USB SEND to do this.

I think I know why this is happening but it is deep in my limited understanding of PC architecture and I will keep it to myself until I can prove it.

I heard from David, GM4JJJ, who found the same problem using USB SEND.

You could get away with using meteor scatter 5 seconds late, but you would lose that proportion of your transmitting time. Meteor scatter is hard enough without discarding almost 10 percent of your transmission. It might work for most of the time, but I run the sort of station which needs 100% of his chances to be heard.

It might work with that limitation for FSK441 and JT6M, but it definitely would not work for JT65, WSPR or similar modes where the start timing is crucial.

So, for now, I am sticking with CAT7200. That is a little bit of software which converts the RTS signal from WSJT10 into a CAT message which the IC-7300 can understand. It is very fiddly to set up but it seems to work OK. You find it here

If anyone out there can work out how to get around the 5 second delay with USB SEND no doubt you will let us all know. In the meantime Greg, SP3RNZ, has set out a good explanation of how to use USB SEND, in his case with MSHV software. Greg's page is here

Greg's posting has encouraged me to have a close look at MSHV software, and I will report on that soon.

Nice 4m FSK QSO today with Jerzy, SP8HWY. After a long period when meteor scatter was not delivering many contacts, I hope this points the way to increased activity. Jerzy is a regular and someone whose dedication to VHF work is much appreciated. Keep up the good work OM.




  1. Hello, in the IC-7300 Menus for Connectors --> CI-V, Unlinking CI-V USB from Remote and making sure CI-V USB Echo Back is turned ON seems to solve the 5-second delay when using WSJT in CAT PTT mode.

    VY 73, Tony 3D2AG

  2. Hi Tony.
    Right now my settings under CI-V are:-
    CI-V Transceive "ON",
    USB Echo Back is "OFF", and
    CI-V USB Port is "Link to [REMOTE]".