SignaLink and Other USB Digital Interfaces – Huge Bug + Fix for Amateur Radio Digital Modes

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US Amateur / Ham Radio operator Jon, KD9DAL has discovered a bug which affects digital performance of nearly all amateur / ham radio equipment that uses USB connections to a computer.

Devices include but not limited too

  • All Icoms with built in USB Audio
  • All Kenwoods with built in USB Audio
  • All Yaesus with built in USB Audio, as well as the SCU-17 Interface
  • All Signalink USB’s

Jon has reported a with the USB audio chipset used in many ham radio sound interfaces that occurs in windows vista and later. The affected chipset is the TI PCM2900 series PCM2904 and below, pre-C revisions.

  • All Icoms with built in USB Audio
  • All Kenwoods with built in USB Audio
  • All Yaesus with built in USB Audio, as well as the SCU-17 Interface
  • All Signalink USB’s

If using one of this devices on Windows Vista or later, your performance is reduced due to this bug even if you think the device working fine.

This is confirmed by Texas Instruments, who never recommended this chip set for use on windows Vista and later in the first place, and also tested with more than 50 hams who gained massive receive performance after the fix.

The bug is very odd and has some quirks that bring it back very often even after the fix so I made a detailed video linked below demonstrating the bug, the fix, and showing real measurements of the affected audio on a scope and several meters, and also demonstrating how to properly level your audio in the analog domain and in windows for maximum dynamic range and minimal noise after you fix the bug.

The bug is that this line of TI chipsets identify themselves to Windows Vista and later as microphone devices via the Input Terminal String, even though they are being used as Line In devices. This makes windows add 30db to 50db of gain digitally to the input, clipping your incoming signal. A lot of people I’ve worked with have “worked around” this bug without knowing it by lowering the level slider in windows recording properties panel to very low levels, or by turning their Signalink RX knob nearly all the way down, or a combination of both.

This is very bad, it reduces the dynamic range of your incoming signal pushing it into the noise floor, and most importantly, does not solve the already clipped and distorted waveform due to the unnecessarily added gain. Nothing will return your incoming signal to the pure undistorted sine wave besides the “fix” outlined below, even if you think it’s working well enough now. Trust me, we’ve verified with 50+ people on different setups and radios that performance on modes like JT will double.

For the fix and video demonstrating the problem - http://k3rrr.com/signalink-and-other-usb-digital-interfaces-huge-bug-fix-for-amateur-radio-digital-modes/

New VK balloon Circumnavigates the Earth

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The party-type foil balloon PS-46 from Australia has shown that going around the southern hemisphere is no fluke - although it does need some perseverance.

A very excited but humble Andy Nguyen VK3YT, who launched the balloon carrying an Amateur Radio payload said: “I express a big thank you to everyone assisting with its tracking across the continents.”

The solar power helium balloons in his series use a 25mW transmitter with WSPR, JT9 and sometimes Olivia signals on the 30m and 20m bands. That enables tracking through stations who report on its altitude, speed, direction and battery condition.

He explained that PS-46 flight left Australia at 0700 (AEST) on 25 May 2015, making its epic flight in just over 12 days. 

“This time it was in the right position (before arriving in Western Australia) for the jet stream to push it over land.”
— Andy VK3YT

The balloon did an s-shape over the Pacific to South America, traversed the South Atlantic to Namibia, tracked above South Africa, crossed the Indian Ocean to Cape Le Grand near Esperance West Australia, and completed the world trip on Thursday, 4 June 2015.

After reaching Australia the balloon tracked inland from South Australia (VK5), just touched New South Wales at Cameron’s Corner (three state border point) and then to Queensland making the circulation complete.

Earlier balloon PS-41 launched by Andy VK3YT was the first to circle the earth. On its second time around it visited the Antarctic region, but disappeared in the Southern Ocean around 21 April 2015.