Lesson Learned

Steve W3HF

I learned today that Yaesu's Digital Noise Reduction (DNR) and PSK31 don't mix well together.

I had been wondering why many of the signals on 20m were distorted. I didn't have the problem on 15 or 10, but 20 was different. On some signals, I didn't get railroad tracks on the waterfall. Signals were strong enough (based on color and brightness) but it was an almost-solid blob.

On this trip I'm using a Yaesu FT-2000; the FT1000MP Mark-V that I used last time is broken. With a little bit of playing, I figured out much of the rig, but still had that problem on 20m.

So today I started paying close attention to everything in the display, and correlating the indicators to buttons/knobs on the front panel. And there are a lot of those, 16 knobs and 75 buttons! But when I pushed the DNR button, a "DNR" light on the display went out and the signals cleared up!

DNR is probably a great feature for audio signals, but wreaks havoc on PSK. My guess is that it is destroying the phase shifts. Your ear can't hear phase, so it can be used as a "degree of freedom" (in other words, something to be sacrificed) for audio signals. But for a signal where the information is carried by phase changes (like PSK), it's a disaster!

So, my apologies to anyone who tried to call me and I couldn't decode it. I know what to look for now.


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