It's all about the Software

I'm converting my ham radio computer usage to include SDRC as either the main receiver or as a panadapter. My Icom 7300, the "External Radio" will always be my transmitter. I've run across a weird thing. When running JTDX or WSJT, if "Tracking" is enabled, when I try to transmit, SDRC turns the transmit audio off a second or two later. Or the transmit audio never comes on at all. The radio remains in transmit mode until I or the JT program stops it. If I disable tracking, transmitting works properly. Receive works normally.

FlDigi behaves similarly, except that the External Radio has to be "powered off" in the SDRC External Radio pane.

In either case, if I quit SDRC, then transmit behaves normally. But SDRC and tracking is kind of useful for the non-JT digital modes. Everything was working correctly until I added SDRC's External Radio to the mix.

Here's my setup:

Win4Icom talks directly to the 7300 on COM7. It also provides two Com0Com serial port pairs that can communicate with other programs: COM 16-17 and COM 20-21.
Log4OM uses Omnirig v. 1.2, Rig #1, which is on COM 17.
JTDX and WSJT also use OmniRig Rig #1.
FlDigi doesn't support OmniRig. It uses RigCat, and talks on COM 21.
SCRC "External Radio" is also using OmniRig Rig #1.
All programs run "as administrator" so multiple programs can access OmniRig's multithreading capability.
All COM ports are currently running at 38400 baud.
I'm using CAT commands for PTT. But PTT works. It's the transmit audio that's giving me problems. And only when SDRC is using the "External Radio" function.

I also experimented with a setup that did *not* include Win4Icom. The same basic problem occurred. So the issue appears to be between Log4OM, SDRC and whatever digital program I'm running. Any ideas, anyone?

OmniRig Rig#1 configuration is attached. Rig #2 is the same, except that it talks directly to the 7300 on COM7, for running without Win4Icom.

--Peter, KD7MW

I figured out what's happening. But I don't know what to do about it.

The Icom 7300 has a special "Data" sub-mode that can be added to USB or LSB. USB-Data is the correct mode for the radio to do FT8 (and its cousins"), PSK, AFSK RTTY, Olivia, etc. It sets the receive filter center to a sweet spot of 1500 Hz. It also has its own setting in Set/Connectors that enables or disable various inputs.

When SDRC is doing "Tracking," as soon as I start to transmit, it changes the 7300's mode to plain USB rather than USB data. This immediately cuts off the transmit audio, which is normally set to take input from the Microphone plus the Accessory Socket, but not the internal USB sound card. That was why I was getting no transmit audio. Plus, WSJT, JTDX and FlDigi try to reassert the USB-Data mode, which SDRC appear to misinterpret as Wide-U (24 kHz bandwidth). That SDRC filter mode appears to be what SDRC thinks "Data" means.

I can partially work around this by changing the 7300's setting "DATA OFF MOD" to Mic + USB. Then I get transmit audio in plain USB mode. But the 7300's filters are still in the wrong place in the passband. And the SDRC filter ends up in Wide-U periodically. This renders both receivers not entirely suitable for FT8 or the more conversational digital modes.

I can easily run FT8 without SDRC. But the other, more conversational digital modes would benefit from SDRC's far better spectrum display to find and pinpoint digital signals in FlDigi.

This is not quite a bug, but SDRC, the 7300 and the digimode programs are all speaking slightly different languages, and the result is digital Babel.

Any suggestions? Simon, can anything be done to make this work better?

Suggestions made in the Groups IO forum.

https://sdr-radio.groups.io/g/main/message/77074

73

Max