+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 04 Oct 2000 16:04:31 -0600 From: Larry East Subject: [Elecraft] Noise Blanker Observations Thought I'd add my two (binary) bits worth to the NB discussion: I find that my NB is very effective on an annoying popping sound (mostly on 80M) that I suspect is caused by an electric fence in the area. NB1 reduces it considerably and NB2 removes it completely. I get similar results for certain types of static crashes: NB1 is somewhat effective and NB2 is very effective. However, neither seems to be too effective against electrical noise from drill motors, etc. Back in August a couple of folks posted notes that they had increased C12 on the NB board by a factor of 10 to 20 (thus increasing the blanking gate width to around 1-2 milliseconds) and got much better blanking of electrical noise. So I decided to give that a try. Increasing C12 to 0.1uF definitely resulted in better attenuation (with NB2 selected) of some types of electrical and atmospheric noise. However, it resulted in a rather raspy sounding CW signals. Backing off to 0.047uF worked just about as well on noise and did not produce any noticeable effects on signals. As a result, I have made the following mod to my NB board: 1. Changed C11 from 0.001uF to 0.0068uF (using the original C12 cap) to give an NB1 blanking pulse width of 65-70 us (instead of 10 us). 2. Changed C12 from 0.0068uF to 0.047uF to give an NB2 blanking pulse width of around 500 us (instead of 70 us). Seems to be a good overall compromise for the types of noise that I hear. Your results may vary. 72/73, Larry W1HUE/7 +++++++++++++++ Date: Tue, 03 Jun 2003 13:36:57 -0700 From: Vic Rosenthal Organization: Transparent Software To: Deni Cc: elecraft Subject: Re: [Elecraft] The K2 Noise blanker realy works! KDSP2? Deni wrote: > Just hooked up a random wire to my K2 in a new location in France to find I > can hear a nearby electric fence clicking away. > First time I've used or needed the noise blanker for real and it sure does a > good job, the preamp needs to be on to get the levels right for the NB to do > its thing. Some people with electric fence interference have reported improved blanking in the NB2 position by changing increasing the value of C12 in the NB to 0.22 uf. Apparently the fence pulses are longer than the usual pulse-type noise. It's definitely worth a try. -- 73, Vic, K2VCO Fresno CA ++++++++++++++++++