My K2 S/N 5149 has been up and running well for about 5 years. I finally decided to check out the filter alignment using Spectrogram. I downloaded v.16, and am running it through Wine since I'm using Ubuntu as an operating system. I couldn't get the version on Tom's page to run this way, and right now, I don't have easy access to a Windows machine.
The parameters on the newer version are a bit different than what Tom specifies: 1. The slowest sampling rate is 22K, probably not a problem; 2. To get a 10.8Hz frequency resolution, I need to set the FFT size to 2048 (1024 gives a default of 21.5Hz), again probably not a problem, I can probably even go to a higher rate and get fewer artifacts on the signal; 3. Band limits set from 0 to 2840Hz. I'm using the K2's headphone output to connect to the mic input on the sound card. Its settings are minimal, but I have selected the correct input, and am not adding any amplification. The program does appear to work. I can see the different filter widths, and can move them about the 600Hz cursor to center them. There is a lot of noise riding on the signal, maybe "5dB-10dB" worth. There is a Peak Hold function that shows a reasonable shape to the pass band if I engage it, but the live signal is very noisy. Also, instead of being way down in power, like in Tom's example, to get the baseline of the signal at the bottom, I had to set the spectrum level from -10dB to 60dB (This may be a function of my sound card (?)). I attempted the L34 alignment as also mentioned in Tom's instructions, and that's where the questions really started. The noise level riding on the signal is the same, and there are spikes at 600Hz intervals. The first (@ 600Hz) is about 20dB-25dB above the noisy baseline. The problem here is that L34 is maxed out up. If I adjust it down, the spikes do start to descend into the noise. I am worried that there is a problem with L34, or another component in that circuit that isn't allowing complete adjustment, and causing the noise riding on the signal. I did do this by ear, per the manual, and the tone at 7Mhz did get louder, and the noise did subside, but Tom's comments in the instructions lead me to believe that there should be enough adjustment in L34 to clean up a lot of the trash on the signal. Is there a problem, or am I over-analyzing this, and is the ability to center the pass bands all that matters? Any comments/criticisms are welcome. Thanks in advance. Jim KO5V Sandia Park, NM ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
