K2 - Adjusting L34 with Spectrogram
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K2 - Adjusting L34 with Spectrogram
 
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Decided to try pre-aligning L34 using Spectrogram. However, I've
never played with Spectrogram or anything of the like before. This screenshot shows the best Signal to Noise ratio I could come up with. Does this look about right? http://tinyurl.com/3bd3m2 Internal signal was found right at 7 MHz and I have FL1 (1.50) selected per the recommendation of KE0Z. The -53 dB spike at ~1152 Hz is oddly interesting to me, is this normal? Thanks -- JT Croteau, N1ESE - Manchester, NH _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: K2 - Adjusting L34 with Spectrogram
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JT,
Turn the AF gain (or the soundcard line-in setting) up a bit until the noise in the passband becomes a bit greater. After that, adjust L34 for the greatest difference between the signal and the noise floor. Expect some difficulty in determining the proper point - the peak S/N ratio is still quite broad. If you do not discern any improvement, just set the slug for the greatest amplitude on the Spectrogram display and be done with it. If you cannot discern the difference in S/N ratio with either your ears or with the Spectrogram display, then the setting that gives the greatest amplitude is the correct one (and it is a broad setting). If your 'best' setting is very far from 1 to 2 turns from the top of the coil, then check things again because something is wrong (most likely a soldering problem). The spike is likely a result of pickup from some local source - check the things in your house as a first course of action. 73, Don W3FPR JT Croteau wrote: > Decided to try pre-aligning L34 using Spectrogram. However, I've > never played with Spectrogram or anything of the like before. > > This screenshot shows the best Signal to Noise ratio I could come up > with. Does this look about right? > > http://tinyurl.com/3bd3m2 > > Internal signal was found right at 7 MHz and I have FL1 (1.50) > selected per the recommendation of KE0Z. The -53 dB spike at ~1152 Hz > is oddly interesting to me, is this normal? > > Elecraft mailing list Post to: [hidden email] 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 |
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JT and Don,
Could the weak(-53 dB) spike just be 2nd harmonic of the audio fundamental spike? The main spike looks a bit lower than 600 Hz? Just a thought to save looking for another source of the spurious signal..... 73, Mike, K8CN K2 #5569 Quoting Don Wilhelm <[hidden email]>: > JT, > > Turn the AF gain (or the soundcard line-in setting) up a bit until the > noise in the passband becomes a bit greater. After that, adjust L34 > for the greatest difference between the signal and the noise floor. > Expect some difficulty in determining the proper point - the peak S/N > ratio is still quite broad. If you do not discern any improvement, > just set the slug for the greatest amplitude on the Spectrogram display > and be done with it. If you cannot discern the difference in S/N ratio > with either your ears or with the Spectrogram display, then the setting > that gives the greatest amplitude is the correct one (and it is a broad > setting). If your 'best' setting is very far from 1 to 2 turns from > the top of the coil, then check things again because something is wrong > (most likely a soldering problem). > > The spike is likely a result of pickup from some local source - check > the things in your house as a first course of action. > > 73, > Don W3FPR > > JT Croteau wrote: >> Decided to try pre-aligning L34 using Spectrogram. However, I've >> never played with Spectrogram or anything of the like before. >> >> This screenshot shows the best Signal to Noise ratio I could come up >> with. Does this look about right? >> >> http://tinyurl.com/3bd3m2 >> >> Internal signal was found right at 7 MHz and I have FL1 (1.50) >> selected per the recommendation of KE0Z. The -53 dB spike at ~1152 Hz >> is oddly interesting to me, is this normal? >> >> > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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 _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: K2 - Adjusting L34 with Spectrogram
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On 8/28/07, Michael J Carter <[hidden email]> wrote:
> Could the weak(-53 dB) spike just be 2nd harmonic of the audio > fundamental spike? No, it was a spurious emission from something but I'm not sure what. My latest experiment of playing with L34 and SG is much cleaner: http://tinyurl.com/26hfrb AF Gain was set around 2-o'clock with very little gain on the line input level of the sound card as shown here: http://tinyurl.com/2dzho4 I can get rid of the noise completely as spectrogram sees it but the signal drops about -25 dB. I hear white noise along with the signal when spectrogram sees nothing. -- JT Croteau, N1ESE - Manchester, NH _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: K2 - Adjusting L34 with Spectrogram
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It looks like I goofed in my last screen captures. Here are some new
shots, one for each filter setting, of my tweaking L34 with Spectrogram. 1.5 kHz Filter: http://tinyurl.com/2rla5d 700 Hz http://tinyurl.com/2k9p7f 400 Hz http://tinyurl.com/2lrr8p 200 Hz http://tinyurl.com/3dyj37 I haven't attempted to tune the filters yet as I am not yet finished construction. This is just initial adjustment of L34. -- JT Croteau, N1ESE - Manchester, NH _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
Re: K2 - Adjusting L34 with Spectrogram
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JT,
Those all look good, but really do not tell us much - you have to be the judge of when the peak of the signal has the greatest difference to the noise floor. You really should crank in a bit more soundcard gain - that will allow you to see the noise floor across the entire screen rather than just in the passband. That is often helpful in making an overall judgment. 73, Don W3FPR JT Croteau wrote: > It looks like I goofed in my last screen captures. Here are some new > shots, one for each filter setting, of my tweaking L34 with > Spectrogram. > > 1.5 kHz Filter: > http://tinyurl.com/2rla5d > > 700 Hz > http://tinyurl.com/2k9p7f > > > Elecraft mailing list Post to: [hidden email] 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 |
Re: K2 - Adjusting L34 with Spectrogram
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On 8/29/07, Don Wilhelm <[hidden email]> wrote:
> You really should crank in a bit more soundcard gain - that will allow > you to see the noise floor across the entire screen rather than just in > the passband. That is often helpful in making an overall judgment. I'm going to experiment with a different soundcard as well. I'm currently using the 24-bit soundcard on my motherboard which is supposedly pretty good but still onboard sound and tasks the CPU more than I like. I have a SoundBlaster sitting here that may be a more capable candidate for this task. BTW, for a weak signal, this internally generated signal is very strong. I have a real hard time hearing the noise unless I crank the can down quite a bit. -- JT Croteau, N1ESE - Manchester, NH _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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