Mike AB3AP wrote: I've noticed the majority of K2s seem to be built with the NB. I don't have it, and since I don't seem to be having any man-made noise problems I've been wondering when & where the NB is useful. Is it mainly for presumably noisier urban and suburban areas? Without it would something like Spectrogram show continual spikes at certain frequencies? And finally, would the DSP board have any substantial effect on the sort of man-made noise the NB addresses? Thanks!
------------------------------------- The noise blanker is designed to suppress noise consisting of a train of high-intensity pulses with a regular interval between them. Good examples are the raucous buzz most cheap incandescent lamp dimmers produce or the staccato pops produced by poorly-shielded automobile ignition systems, especially on the higher frequencies. If the noise does not have pulses that occur with very fast rise times and at regular intervals, the noise blanker won't be able to identify it from regular QRN or it won't able properly time the action to suppress the pulses. It does a wonderful job on the proper sort of noise but, like all such noise blankers, it does it at some expense in performance. The blanker actually shuts off the i.f. strip for the duration of each pulse. Instead of a train of loud pops coming through the second detector and down the audio channel, you have a chain of 'holes' where there is no output. The problem is that process of switching the i.f. strip on and off quickly also turns the i.f. into an unintentional frequency mixer. With the noise blanker on, strong signals can mix with each other in the i.f. producing spurious artifacts that sound like everything from normal QRN to actual spurious signals on the band. That's why the noise blanker has an on/off switch. The noise blanker should only be turned on when it's needed. I don't have the DSP unit in my K2 so I can't compare them. The sorts of noise the noise blanker is designed to produce are more likely to be encountered in a urban environment, although sources capable of drowning out the bands might also be in your own home. The noise from cheap lamp dimmers usually doesn't travel very far, for example. The troublesome ones are usually very close by. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
