Frequency Analysis of Key Chirp

During a discussion of key chirp on Phil's transceiver, I offered to do a spectrum analysis of the recordings made by Carl. While listening to selected slices of the audio I concluded that the chirp is most noticeable on the initial character sent on semi break-in and on the first character of a letter sent on full break-in.

I used Cool Edit 2000 to analyze the following slices of the audio waveforms:

• First 30 msec of the first character sent on semi break-in
• Third 30 msec of the first character sent on semi break-in. This allowed some time for the pitch to stabilize.
• First 30 msec of the initial dah sent in full break-in
• Third 30 msec of the initial dah sent in full break-in

The same analysis can be done with the Audacity program.

The annotated screen shots are shown below. Click on any one for an expanded view. All have background noise showing in the upper part of the spectrum. The area of interest is the tone peak around 690 Hz.