by Kevin Strom, WB4AIO
TO PROVE THAT STANDARD AM (a mode that is very close to my heart) isn’t the only HF mode offering good fidelity these days, here’s a 10 MB mp3 audio file I recorded (with one of the Flex SDR-1000s I’ve been experimenting with lately) Labor Day evening of some ESSB operators on 3630 kHz. The band hadn’t completely formed yet, as these Central Daylight Time fellows were propagating to the East Coast at about 7:30 pm their time — full daylight. And static from the remains of Hurricane Isaac was very much present. Yet these only moderate strength signals — some just equal with the static crashes — are still quite intelligible. I think the good intelligibility is because of the wide broadcast-style frequency response, not in spite of it.
It’s amazing what excellent sound some of these experimenters are getting out of single sideband. For years — decades really — only (highly modified to broadcast standards) AM gear was getting this kind of audio quality on amateur radio. But improved techniques have really made SSB sound better than ever!
For best results, listen on a high fidelity set of speakers or headphones:
W9AD / KU8R / K9JSP / WB9DNZ / N9VR on high fidelity ESSB 3630 kHz LSB
I always liked good audio on amateur radio — it allows subtlety of meaning and expression and personality to come through — and disliked the pinched, distorted sound that was the SSB norm for a long time.
To get harmonic integrity (proper frequency relationships of audio overtones) on high fidelity SSB, everybody in the group — and your receiver — has be within maybe four Hz of each other. Anything more than that, if you have a good ear, and you start to notice that it doesn’t sound quite right.
The SDR-1000 is just barely passable for such use (calibrate, calibrate, calibrate), but I am planning to modify it to use a rubidium frequency standard — then it should be within a milliHertz or two of perfect accuracy. At that point, I’ll only have to worry about the other stations!
Here’s a screen shot of the virtual front panel I am using:
I added the TMC logo to the panadapter — my favorite old-line HF radio manufacturer.