I made an attempt to plot the noise blanker performance and log the results in an Excel spread sheet. I found that the test was in valid so I used a different approach.
The test involves using a function generator that's built into my Agilent DSOX3024. The generator is set for pulse mode with a 200mv P-P pulse repeating 15.5 every 15ms. The pulse rate is similar to a car with a bad ignition system speeding by your ham shack. To insure that there's no RF getting back into my very expensive oscilloscope, I connected the generator output to the K3's RX port. The settings were adjusted by listing to the noise at the speaker. I determined that without the DSP or the I.F. noise blanker turned on there are "sweet" spots and "hot" spots. That is the sweet spots are where the pulse width is adjusted so that the noise is minimum and the hot spots are where the noise is maximum. I found that every 70ns, there’s a sweet spot and 35ns form the sweet spot there's a hot spot. Adjusted the pulse width from 20ns to 1 ms and the hot spots and sweet spots were right on target. So what does this mean? There conditions where you can have a motor, car or any electrical device that generates a pulse with in the sweet spot will never be heard on you K3. On the other hand there are conditions where the noise source generates a pulse width that’s with in the hot spot, will the noise blanker effectively reduce the noise. In my original test I didn’t know that there were sweet and hot spots. I ran the test by simply turning the NB and adjust the NB level. My new approach is a lot more simple and doesn’t require checking every sweet and hot spot All settings from NAR1 to NAR4 are totally useless. It offered no noise reduction regardless of the pulse width and pulse rate. Settings from NAR5 to NAR7 were somewhat effective but the noise reduction was spotty and the noise level would vary every 5 or 6 seconds. MED 1 and 2 are useless settings and MED3 is spotty. MED4 to MED7 reduces the noise considerably. The same is true for WID 1 and 2. usless! WID3 is spotty and WID4 to WID7 are the best settings. http://elecraft.365791.n2.nabble.com/file/n6848682/k3_blkr.bmp ----- Jack WA9FVP Willco Electronics -- View this message in context: http://elecraft.365791.n2.nabble.com/Noise-blanker-test-tp6848682p6848682.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
