In a message dated 30/04/05 16:12:07 GMT Daylight Time, [EMAIL PROTECTED] writes:
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? Reply: -------------------------------------------------- At first I thought the KNB2 noise blanker in my K2 was not working as it had no effect on the normal type of noise received at my QTH. Then after quite a few months found that the NB did indeed work and very well, but only on impulsive noise with sharp rise times like automobile ignition interference. Seems that the KNB2 is a lot more selective in what it will suppress. My old faithful Yaesu FT-480R 2m multimode on the other hand is not as choosy and will work over a wider range of noise types. The FT-480R if anything is rather simpler in the NB circuit design than the KNB2. The FT-480R picks up the RX wide band input half way through the two roofing filters that provide initial bandwidth control after the first mixer. It uses a relatively high gain IF section controlled with AGC to feed a detector circuit that gates G2 in the 2nd mixer MOSFET. It does work exceptionally well though, removing a variety of noise types. If the KNB2 worked to the same degree I would be very happy. The incidence of the type of interference that the KNB2 will gate out is seldom experienced at my QTH, so it gets very little use. In retrospect could have saved a some money by leaving the KNB2 out in my K2, though as has been pointed out in other postings there are some QTH where this noise blanker is really useful. Only hope that eventually some future mod or redesign of this module may be of benefit with the type of noise I suffer from. As regards use of the DSP2, I do not have one in my K2, but do have an external Timewave DSP-9+ available. The DSP-9 works I would guess in a similar way to the DSP2 in that it is in the audio chain. Impulsive noise is not removed by this device in noise reduction mode (NRr), though longer term noise that the normal noise blanker will not touch is suppressed in amplitude during it's duration. I would guess the audible effect is in a way similar to what used to happen with ANL circuits in the AM days. The DSP-9 and would presume other audio DSP devices have a longer delay in response time and so prevent any chance of removing sharp rise time noise. Though it may be looked on as heresy by the K2 CW fraternity, in the Timewave DSP-9+ SSB mode, morse can be almost completely eradicated by the action of noise reduction on tone (NRt). When going over to CW with an external DSP device, the user has to be careful that this NRt facility is switched off, otherwise little morse is heard. Bob, G3VVT K2 #4168 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
