27sep05 measurements of the 430ch cal
28sep05
The 430 carriage house cal was measured on 27sep05
in the carriage house using the network analyzer. The system was connected
to the network analyzer and the Tsys (this did not include the sky) was
measured. The cal was then turned on and the Tsys was remeasured. The difference
in the two measurements is the cal value. This was done for the 4 settings
of the cal selection (must switch in attenuators after the diode). It was
also done at a set of frequencies. The plots show the measured cal values:
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PolA cal
values (.pdf):
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Page 1: This is the data for polA. Col 3 is Tsys with no cal (and no sky).
This temperature (receiver or flange) is about 43K. Col 4-7
are the Tsys values in the 4 cal selector positions (the names are the
old cal values). The last 4 columns are the new measured cal values
for the 4 positions.
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Page 2: This plots the cal value versus frequency. The highest two cal
values have a sine wave of about 40Mhz period, the lower ones don't. These
different cals are selected by a set of attenuators after the noise diode.
The higher cal values have lower attenuators. The sine wave is probably
a bad match between the diode and something downstream. The attenuators
for the lower cal values are attenuating this standing wave. The length
of the cabel for the standing wave is 150/40=3.75 meters in air. If the
velocity in the cable is .7 c, the length would be 2.6 meters.
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PolB cal
values (.pdf):
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Page 1: The data for polB. The column format is that same as polA (described
above). The flange temperature for polB is 27K.
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Page2: The cal temperature versus frequency. The higher cal values
(smaller attenuators after the diode) also have a ripple with a period
of about 20Mhz. This is about twice the distance for the ripple in polA
(7.5 m air, 5.25 m cable).
The difference in the flange temperatures for polA and
polB is 16 K. This is coming from the monoplexor connected to PolA. The
430 xmiter is single pol. polB is set to load during the transmissions
while the polA receiver is switched between receive and protect via the
monoplexor.
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