On Sun, May 29, 2011 at 4:17 PM, Kerry Miller <[email protected]> wrote:
> Here's my question. Since the NB is really done in software on the Flex, > is > there a way to have a noise blanker (NB3 maybe?) that ONLY works inside the > passband of the filter? If it was possible to do this maybe it would > eliminate the noise (like my perpetual powerline noise) inside the filter's > passband but not be affected by the strong signals outside of the passband. > It is not a bad idea but it does help to understand how a noise blanker works. Noise pulses are very narrow and very fast. If you look at them in the frequency domain you will see that their spectrum is very broad. That fast rise and fall time requires wide bandwidth to detect. After you detect the pulse, you then blank the IF for the duration of the pulse. Basically the receiver is "switched off" for the duration of the noise pulse. The problem with strong signals is that they are falsely detected as noise pulses and cause the IF to be blanked. This is a form of amplitude modulation that creates sidebands around every signal. Not good. But it is potentially possible to make a NB that will be able to recognize the difference between a very strong narrowband signal outside the passband and a broadband noise pulse and NOT blank the receiver for strong narrowband signals. But, right now, that software doesn't exist in PowerSDR. The good thing is that there has been talk of writing such a noise blanker and including it in PSDR. -- Brian Lloyd, WB6RQN/J79BPL 3191 Western Dr. Cameron Park, CA 95682 [email protected] +1.767.617.1365 (Dominica) +1.931.492.6776 (USA) (+1.931.4.WB6RQN) _______________________________________________ Flexedge mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for posting topics related to SDR software development and experimentalist who are using beta versions of the software.
