Re: [Discuss-gnuradio] improper WBX transmission of tone in center of spectrum

[George Nychis]

Thanks for the help, Matt.  I never actually knew what DC offset was until now ;)  Learning as I go!

From what I understand, the USRP2 scales between -1.0 and 1.0.  I am trying to boost my transmit power well over the power of the DC offset. I think that if I increase the gain, the DC offset is also boosted.  So I am trying to boost my signal over it (for this 75dB separation).  I am scaling my samples to the -1 and 1 range, but I am not seeing that much separation after scaling:

http://cyprus.cmcl.cs.cmu.edu/~gnychis/boost.jpg

That's about a 5dB separation after scaling.  I am not adding any attenuation, and this is conducted.  I am also configuring the gain to 0, so as to not boost the DC offset either.

Thanks for the help, I appreciate it.

- George

On Wed, Aug 4, 2010 at 2:59 AM, Bob McGwier <address@hidden> wrote:

That is an awesome amount of LO suppression in an SSB mixer based system (I mean the power 1/330000-th of the LO).  A more interesting number given this level of LO suppression would be the introduction of a tone (say) above the LO at LO+F and to see what the power is at LO-F (the image).

Bob

On 8/3/2010 4:55 PM, Matt Ettus wrote:

The WBX can put out about 20dBm at 520 MHz. -55dBm would be 75dB below
the desired signal, which is quite a good amount of LO suppression. If
you need more, you'll need to actively calibrate the DC offset to null
it out.

Matt


On 08/03/2010 12:55 PM, George Nychis wrote:

The power of the tone comes in to the spectrum analyzer at -55.6dBm

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