Message	Date	From	Subject
5869	2011-02-22 11:11:25	Bob	An Audio Noise Generator - Followup
Hi All - This is my second attempt to post this today - first time didn't seem to work - I don't see it - so here goes again: ............. In my recent posting I noted that at that time I had not yet applied my new noise source. Since then I have built the filter circuit of Fig. 3.50 in "The Book" as a "test case". (This filter is presented as a SSB condidate.) I then exercised this filter three ways including a manual test, with the noise source, and with an experimental audio sweep source / detector combo. I have added two .jpg and one .pdf to the Files folder "Audio Noise Generator" showing the results. Look for file names beginning "Fig 3.50". You can compare what I got with EMRFD Fig. 3.51. It's fair to note here that I built the filter circuit with parts on hand (not selected) so some departure from the published response is not unreasonable. Also, the experimental audio sweeper / detector combo is somewhat deficient in frequency linearity and output calibration respectively - but even so the comparitive results are not too shabby, I feel. At this point I feel Spectrogram gives a reasonable overview result but lacks the "fine grain" available with a point by point - or better yet - sweep - of a circuit frequency response. In any case this has been a fun pursuit! Cordially, Bob K3NHI

Hi All -

This is my second attempt to post this today - first time didn't seem to work - I don't see it - so here goes again:

.............

In my recent posting I noted that at that time I had not yet applied my new noise source. Since then I have built the filter circuit of Fig. 3.50 in "The Book" as a "test case". (This filter is presented as a SSB condidate.) I then exercised this filter three ways including a manual test, with the noise source, and with an experimental audio sweep source / detector combo.

I have added two .jpg and one .pdf to the Files folder "Audio Noise Generator" showing the results. Look for file names beginning "Fig 3.50". You can compare what I got with EMRFD Fig. 3.51.

It's fair to note here that I built the filter circuit with parts on hand (not selected) so some departure from the published response is not unreasonable. Also, the experimental audio sweeper / detector combo is somewhat deficient in frequency linearity and output calibration respectively - but even so the comparitive results are not too shabby, I feel.

At this point I feel Spectrogram gives a reasonable overview result but lacks the "fine grain" available with a point by point - or better yet - sweep - of a circuit frequency response. In any case this has been a fun pursuit!

Cordially,
Bob K3NHI