I know there has been lots of discussion but I just made a change which
solved everything. I noticed that the peak was at the top most rotation of
L34, so I changed C182 from 180pf to 120 pf (npo). Now, using an external
sig gen, not the 7k birdie, there is a pronounced peak about halfway down
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
On 8/29/07, Don Wilhelm [EMAIL PROTECTED] 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
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 [EMAIL PROTECTED]:
On 8/28/07, Michael J Carter [EMAIL PROTECTED] 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:
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
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
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
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