Hello,
Sorry for the newbie question. Please
flame me directly, not on the amsat-bb.
Am I correct in stating that the doppler
shift of a receive frequency starts higher than the actual frequency as it
is approaching then continues lower as it going away?
Yes if "it" means the approaching
satellite.
Does the frequency appear to stabilize
when the distance from the satellite to the qth becomes constant, even if it
is briefly?
Actually, the distance from the satellite to the qth never
becomes constant (unless you are measuring a point on the curve of doppler
shift) which means that it might seem constant for a moment, but is still
actually changing. As the satellite approaches the nearest point to your
qth, the doppler shift decreases with time until it reaches the point of
minimum distance, at which the doppler shift is zero. Almost
instantaneously, the doppler begins to change again, slowly at first and
continues to increase with time until it drops beyond the
horizon.
A common analogy is that of an approaching train whistle.
The tone of the whistle appears high pitched at first, and slowly begins to
decrease as the train approaches. When the train is at the nearest point to
you, it appears to be the actual tone of the whistle, and almost
immediately, it begins to fall in pitch as the train passes.
Bobbie KD4LV
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