[Discuss-gnuradio] spectral purity (or, weaver not ready for prime time)

[Chuck Swiger]

Gang - Here's a disturbing display of the spectrum about my weaver generated
ssb signal - there were lumps where there shouldn't be so I turned up the 
resolution:

http://webpages.charter.net/cswiger/weaver_spectrum.jpg

this is with the duc center freq at 3900e3, carrier freq at 27e3, and an 
audio signal at 600hz, LSB.
You can see the main peak right where expected at 3926.4Khz, (3927e3-600), 
but there's
other junk not far down - there's something at 3905.6, which would be a 
3905 carrier USB,
another one at 3894.34 (likely 3895 LSB), 3873.6, which would be 3900e3 - 
27e3 + 600, the
negative freq of the main signal (3873Khz, 600hz USB) - and a really 
bizarre one out at 3958.3
that I can't explain at all - it's a little further out than 27e3 X 2, and 
not reflected about 3900e3.
All of them can be heard in a nearby receiver.

So I'll have to track down their origin and fix (somehow) before jumping on 
20meter psk31
anytime soon. A pure usrp tone doesn't have those issues - only my weaver 
graph.

--Chuck
kb4new