Many thanks to SWLing Post contributor, Steve Yothment, who writes:
[Below, you’ll find] my reception report for the digital decode of the Fldigi message by Dr. Kim Elliott on The Mighty KBC (6040 kHz) Saturday night:
I took Kim Elliott’s suggestion and listened to The Mighty KBC on 6095 kHz on Sunday morning using the Utwente WebSDR which receives signals in Enschede, in the Netherlands.
The Mighty KBC finished their last broadcast on 6095 kHz at 11:00AM our time. I recorded their program, but the file is big. So, attached is the last 4 minutes of their program (click here to download), as received by the WebSDR:
It’s too bad that The Mighty KBC is shutting down!
Many thanks for both your decoded message and your recorded audio, Steve! I agree: it is too bad the KBC had to shut down their 6095 kHz broadcast.
“Yes, modern radios usually have a micro communicating with the DSP IC through I2C communications.
The inter-IC communications includes a clock and data line. The clock for I2C is typically 400 kHz nowadays. Harmonics from this clock line are probably the source of the interference.
The manufacturer should have designed the product to ensure that this interference does not occur. It may be that they resolved it at one time but with limited manufacturing quality and component substitutions that often occur in mass production, the problem is occurring now even though it may have looked OK earlier in development. At least, that is my experience with such things. (I used to design car radios for the Panasonic Company.)
Many thanks for your comments, Steve! I recall a similar metronomic sound on another DSP-based radio, but can’t remember which model. I need to dig through my reviews as I’m sure I noted this. I believe checking 400, 800 and 1600 kHz will become a standard checklist item when I review DSP-based radios.
[STF Radio QSL card front (above) back (below). Original scans by Steve Yothment]
SWLing Post reader, Steve Yothment (WD0HGB), writes:
“I received an “audio QSL” card from STF Radio International a few days ago. Have you heard about it? [The QSL] actually has grooves on the card that you can play on a phonograph. I had a friend play the audio on his phonograph and he converted the audio to MP3 format. Then, I decoded the digital info in the file.”