[Elecraft] K2 - Adjusting L34 with Spectrogram

[Michael J Carter]

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 <w3fpr at embarqmail.com>:

> 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: Elecraft at 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