I posted a reply about measuring "microchirp" yesterday but it never made it
to the list. Here's my second try:
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>>You can't. In fact, I know of no electronic instrument capable of
>>reasonably detecting it. Sometimes the ear is the best judge. The keyed
>>waveform oscilloscope display has no association with frequency shift.
>>-Paul, W9AC
In fact, you can. You need an instrument that can capture a signal without
missing any data and then play it back while displaying frequency vs. time.
Such an instrument is called a vector signal analyzer.
The VSA scrolls through a display of the spectrum of the signal. In this
way, the horizontal axis is frequency and the vertical axis is time. If the
plot is in color, the color can represent amplitude. This type of display
format is called a "spectrogram". I think some PSK-31 programs (like
Digipan?) show the spectrum; just imagine successive spectra scrolled in the
display. It's hard to describe.
Markers can be used to measure delta freq and delta time. This is how folks
measure the start-up transient behavior of PLLs and other oscillators, and
how law enforcement agencies positively identify a specific transmitter by
it's start-up "fingerprint".
Al W6LX
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