new amps installed Aug14
The sbn Chalmers amplifiers were damaged Aug13
during an sband run. The sband hi amplifiers were installed in sbn
while the sbn amps were being repaired.
We received the repaired Chalmers amps and began installing them
- The polB (labeled inside the dewar) amp was installed
- This replaced the old sband hi amplifier
- the cables from the amps to outside the dewar are swapped, so
the new amp will be PolA on the outside world.
- jul14: new Chalmers amp installed (polB in dewar, polA outside
- 31jul14: calibration run. single pattern on each of 3 sources
- 06aug14: polB rf cable (dewar to if/lo blue cabinet) found to
have a bad outer shield. repaired.
- 19aug14: calibration runs on two source done
The plots show the results of the
runs (.ps) (.pdf)
- B0017+154, B0138+136,
were done prior to repairing the polB rf cable
were measured after the polB rf cable was repaired
- Page 1: stokes I gain,tsys,sefd,beamwidth
- The SEFD for B1843+098 is a little high
- This could be a problem in the flux, or
- Tsys was probably a little higher since this source is
close to the galactic plane
- Page 2: polA,polB separate, gain,Tsys,sefd
- + is polA, * is polB
- The gain for polA is higher than expected. It is 20% higher
- these sources are not circularly polarized, so the
gains should be equal
- The sefd for the new amp is about 10% better than polB
- B1843+098 is the exception. It's sefd for A,B *,+ are
about the same.
- Not sure how galactic polarized power could make a
difference in 2 circulars?
- The cals were not remeasured (for that matter they weren't
remeasured when the sbh amps were installed).
- the cal value for polA is probably too large. This makes
the gain and Tsys too large.
- The cal value for polA is probably about 10-20% too high
- the new Chalmers amp works better than the old Chalmers amp
- Fixing the rf cable between the dewar and the blue cabinet did
not change the Tsys.
- The source B1843+098 does not show a difference in polA,polB
- the only difference i can think of is that this source is
close to the plane of th galaxy.