KA5MIR wrote: > At my noisy qth, I have to use the noise blankers. This results in strong > signals OUTSIDE the filtered bandwidth, anywhere in the 96kc passband, > modulating the noise blanker INSIDE the filtered frequency range. It often > causes desired signals in the filtered range to be unreadable. > > I would gladly trade spectrum display sensitivity outside the filter range > for narrow passband filtering pre blanker or detector. It would make the > difference between being able to hear stations or not. Of course it would > need to be -Optional- and ideally, adjustable. > > You could probably have a separate detector drive just the spectrum display > if you wanted to maintain a full range spectrum display with the pre-filter > on. > > Maybe there is a way to apply the noise blanker to only the filtered audio > in DSP? > > I've tried a range of settings for the blankers, sampling rates and agc, > but can't get rid of this problem. > > 73' > -Jeff > > This is an excellent question and the answer is theoretically yes with a few caveats. Here is why.
The DttSP software will be deriving an impulse response for the receive chain after an ECO for the SDR-1000 (to eliminate impulse overload) and with the Flex 5000 series. This impulse response COULD BE filtered by the filters to provide a "filtered impulse response". The impulsive noise that is clobbering you will then be detected and after the amplitude and phase of the impulse is determined, it will be subtracted from the receiver. This can be done before the filter or after the filter. The detection after the filter will be more prone to error. SO, it remains to be seen if we can make the detection simultaneously sensitive enough to work and at the same time have a low enough false positive detection rate to be useful. Good question and I will certainly try as it has been a interest of mine for almost two years. With the Flex 5000 hardware, I have finally been able to get textbook pulses and pulse trains and this also led to an immediate diagnosis of the problem with the current SDR-1000 impulse generator that will lead to an ECO to make this work for it as well. Expect this code to show up in dttsp 2.0 under the sdr_linux repository and in the sdr-x repository as it becomes usable. Bob N4HY -- Robert W. McGwier, Ph.D. Center for Communications Research 805 Bunn Drive Princeton, NJ 08540 (609)-924-4600 (sig required by employer) _______________________________________________ FlexRadio mailing list [EMAIL PROTECTED] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
