Fldigi and upgrading to OS X 10.11 El Capitan
For those readers who may be fans of Fldigi, you may want to read the following before upgrading to OS X 10.11 El Capitan later this month. There have been several reported problems with interaction between El Capitan and Fldigi and the precise cause has yet to be nailed down.
Dick, AA5VU, shares that he has had problems with Fldigi, his TS-590S, and El Capitan; after just a few transmissions the waterfall will hang or freeze and will leave the TS-590S PTT keyed with no audio going in or out. Working with the developer of Fldigi, W1HKJ, Dick has shown that Fldigi is not to blame and points to either OS X 10.11 or perhaps the Silicon Labs drivers as the culprit. If it is the drivers, then this problem would likely also exist in all transceivers using this chipset, including those by Yeasu, Icom, and Kenwood. These problems persist even in the El Capitan Gold Master Candidate, but were never present in OS X 10.10 Yosemite.
Additionally, I have personally experienced issues with my US Interface (now Timewave) Navigator losing audio input (and output?) after several minutes of operation; although with far less regularity than Dick has experienced. In my case, the incoming audio would freeze, but the waterfall would continue to show systemic noise, but without any actual signals coming in. The fact that the Navigator uses FTDI drivers would tend to point the blame away from a pure driver issue and back at OS X 10.11; although this setup has not been tested on the Gold Master Candiate release yet. I have not experienced any issues with PTT locking up or other such symptoms. Furthermore, my issue seems to be cleared by simply unplugging the Navigator’s USB connection and reconnecting it, thereby resetting the USB Audio CODEC connection.
Other suggestions have revolved around some reported changes that OS X 10.11 El Capitan has made to the USB API that could be affecting USB-connected audio (and control?) devices, although further details or confirmation are not yet available, likely due to developer Non-Disclosure Agreements.
So, in short, if you are a big user of Fldigi, you may want to steer clear of OS X 10.11 El Capitan until the issues can be completely identified and corrected. If anyone has any information regarding these issues, or has conducted any testing with OS X 10.11 and confirmed (or refuted) these issues with their transceivers and Fldigi, feel free to share comments and let everyone know about your observations.