On 21/06/2021 04:48, Yvon AE7YD wrote:
the issue you describe is often due to MS Windows deciding to power down USB audio devices it thinks are not being used. You must disable the power management options for each USB Hub Device listed in Windows Device Manager under "Universal Serial Bus Controllers" (right-click device, select Properties, then Power Management, and uncheck the allow option).
You also must disable the USB Selective Suspend option in the Windows "Power Options->Change plans settings (on the current plan)->Change Advanced Power Settings" open "USB settings", then "USB selecting suspend setting", and click the "Plugged in" option to select Disabled.
As Bob, G8HGN, points out, there is another issue with HDMI monitor connections. HDMI connections include a USB audio connection which too can be unexpectedly powered down when a screen-saver or power-saver function activates. I don't know of any settings to stop that other than making sure graphics card/chip power management settings for the monitor and screen saver are disabled, YMMV.
The root problem is that USB devices are "hot-pluggable" and adding or removing a device, while the system is running, will cause all other devices to be re-enumerated, this can change device identities but Windows does not inform applications using them that they have been shuffled.
Note this issue affects audio devices but not virtual serial ports like those often used for CAT control, virtual serial ports over USB connections seem to be capable of blocking such power saving options, presumably because they are one-to-one connections and Windows can be sure when they are in use.