Rick, there are irregularities in my noise - and in the previous utility line noises I've had at my QTH - that prevent any predict-the-exact-time-of-the-noise-spike-in-advance algorithms.
Although my sample size is small the experts have told me that randomly raucous 2-4 spikes every 120Hz I see is entirely typical of lightning arrestor faults. To show you the irregularities, here is the impulse envelope, recorded during daylight on 1.8MHz with a 20kHz wide filter and AM demodulator. Notice the overall 120Hz repetition, but inside that there is a substructure where evidently several arcs occur in the lightning arrestor each cycle and the exact number and timing of those vary from cycle to cycle: http://n3qe.org/n3qe-noise-structure.png And here is a short audio wav so you can hear some of raucous noise structure. http://n3qe.org/SDRSharp_20200120_210017Z_18050000Hz_AF.wav Tim N3QE On Tue, Jan 21, 2020 at 11:50 PM Richard (Rick) Karlquist < [email protected]> wrote: > The Kalman filter still generates a blanking pulse like the conventional > circuit. Feedback loops adjust the width and timing of the blanking > pulse. "Amplitude" is not applicable. The frequency of the blanking > pulse is supplied from the power line in the shack (EG 60 Hz). The > feedback loops average over many pulses and therefore suppress QRM > since it averages out in the long run. > > Again, this was all published many years ago. > > Rick N6RK > > On 1/21/2020 10:30 AM, Jim Brown wrote: > > On 1/20/2020 2:28 PM, Richard (Rick) Karlquist wrote: > >> In most cases, line noise is a repeating function with a frequency of > >> 50 or 60 Hz. To make an effective noise blanker in a contest, you > >> simply have to make a filter that only responds to harmonics of the > >> line frequency and then generate the inverse function from a 50 or > >> 60 Hz line clock. > > > > Unfortunately, that's too simple. For effective cancellation, that > > inverse function must be precisely in phase (degrees, not polarity) and > > equal in amplitude at each harmonic frequency. > > > > 73, Jim K9YC > > _________________ > > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > > > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
