[amsat-bb] Seat me straight - CP

["Ben" <b-fisher@xxxxxxxx>]

It is my understanding that CP as defined by AMSAT is from the transmitters
point of view. So if you stood behind a CP transmit antenna and could see
the rotation of the signal as it left the antenna and if it were rotating CW
than its right hand polarization. On the other hand if you were standing
behind the satellite as it received the signal it would be rotating CCW. Its
important for all parties to understand the entire definition. For instance
in the world of commercial Satellite TV, where the ratio of receivers to
transmitters is great they may have the urge to define the polarization at
the receiver end. This would simplify having to explain to lay people way
the signal they are observing is rotating CCW when it is defined as right
hand polarization. There seems to be a lot of confusion and misunderstand of
these concepts among some of our local hams.
   On another point. In true CP the rate of spin or the period of one
complete rotation of the field should equal that of the transmit frequency.
In other words if you are receiving a frequency on 430 Mhz than the rotation
of the field should be at 430 Mhz. In effect if one were receiving a true CP
signal from a satellite than the effect of using a CP antenna versus a LP
antenna would only be a reduction in the signal strength. This would not
account for the fading that is heard on many of the birds. Satellite tumble
or rotation most likely being the cause. In this case would it not be
necessary to use CP? Sure it would help, but wouldn't just a cross polarized
antenna do the some? How many of the birds are using true CP?
Ben K9BF

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