[Elecraft] unequal power output per tone in FSK

[Kok Chen]

On Jan 10, 2011, at 3:35 PM, Wayne Burdick wrote:

> The effect on transmission bandwidth is  negligible, and it's also extremely unlikely to affect copy.


Hank W6SX had written to ask me for a rough guess of transmission bandwidth when there is a 1 dB difference in level between mark and space carriers. 

A rough guess turned out to be relatively easy and the bottom line is that the far off QRM is only about 10 dB down from a phase NON-continuous case of FSK generation, if the mark and space signals are different by 1 dB.  Basically, about 10 dB down from the first plot in this web page:

http://homepage.mac.com/chen/Technical/FSK/Sidebands/sidebands.html

The ideal FSK phase continuous signal should look like the second plot on that page.

So, forget about phase noise!  Your FSK keying sidebands are going to be a much bigger problem for your nearby neighbors :-).

I think that a judicious choice of tone pairs could help, but it is a band-aid, not a technical solution.

73
Chen, W7AY