[TenTec] ARRL Phase Noise Data Plotted to 1 MHz

[Kim Elmore]

I've been thinking, too. A square wave has an infinite number I'd odd harmonics, not all harmonics. Regardless, it's an excellent way to look at IMD, far better than two tones. 

What if we modulated the TX with pink noise? That really does have everything in it. Make the pink noise much wider than the expected audio bandwidth. Ideally, the spectrum should be limited to the TX filtered BW. Wouldn't this be nearly the most severe test?

Kim N5OP

"People that make music together cannot be enemies, at least as long as the music lasts." -- Paul Hindemith

> On Jul 28, 2014, at 11:23, Jim Brown <k9yc at audiosystemsgroup.com> wrote:
> 
>> On 7/27/2014 10:27 PM, Jim Brown wrote:
>> Off list.
> 
> Well, I meant to send it off list, but it was late. :)
> 
>> 
>> I've been thinking about this.
> 
> Overnight, I thought some more.
> 
> The keying waveform is, fundamentally, modulation of a continuous carrier by a waveform that approximates a square-wave -- hence the name CW for continuous wave. ANY square wave has an infinite number of harmonics, the relative strength of which depend primarily on the shape of the switching waveform from on to off and off to on. The faster the rise time, the more harmonics, and those harmonics will be stronger. Those harmonics show up as sidebands, and the higher the order (harmonic number), the farther they are from the carrier. In a rig without IMD, that would be the end of the story, but real amplifiers have IMD, so those harmonics produce IMD, which results in more sidebands.
> 
> Rigs with cleaner keying reflect the skill of the designer to minimize the harmonic content of the keying waveform, the level of TX IMD, and TX phase noise.
> 
> Close to the carrier, the key click spectra plots pretty much tell the whole story of what the TX is doing, because they include the effects of the keying waveform, phase noise and IMD.  As we listen farther off frequency from the transmitter, all that's left is phase noise.
> 
> 73, Jim K9YC
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec