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Intro

• 1.5 degree strips (24 crosses on the 430 yagi and 4 crosses with the linefeed) were done
• The yagi feed adds the polarizations together. The lrr1 polarization of the linefeed was used for the 430 linefeed measurements.
• The signal was centered at 430 Mhz and was passed through a 1 Mhz butterworth IF filter. Each strip took 90 seconds. The signal was detected with a .02 sec time constant and then  sampled at 100 hz.
• At the beginning of a set of crosses, the cal was fired for two seconds to measure Tsys. The cal values used were: yagi cal:124.9, linefeed cal: 192.6 K.
• 2d gaussians were fit to each cross. The fit included a rotation angle for the ellipse as well as a linear term in za (for changes in tsys). The first sidelobes were excluded from the fit.
• The flux used for the source was 24.3Jy
• There was a problem with the yagi. There were glitches in the tsys that lasted for a few seconds. These glitches were seen in the 12feb06 data. At that time it was thought that they were caused by water in the hybrid. The hybrid was cleaned and resealed for water and they were seen to go away. For whatever reason they are now back (although not as often as 12feb06).

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The 29may06 data  (top)

• Fig 1 shows the individual strips:
• Top: yagi strips on 3C286.  Black are azimuth strips, red are za strips. The data has been smoothed by 5 samples. You can't  see the jumps too easily when over plotting all the strips (but they are there).
• Bottom:  line feed strips.
• Fig 2: The average of  the yagi strips after removing the system temperature. Each strip was rotated by the measured pointing error before averaging. The az strip is black and the za strip is red. The top plot is linear (in degK). The bottom plot is db below the peak.  The za beam width is a little larger than the az beam width. The az sidelobes are 9 db and 30 Amin from the peak.
• Fig 3 has the Gain and Tsys.  The gain is about 1.6 K/Jy. Tsys in 455 K at za of 10.5 and goes up to 470K at a za of 18.
• Fig 4 : sefd and beam widths. The top two plots are the sefd (source flux needed to equal the system temperature). The bottom two plots are the beam widths from the fits. * is the azimuth beam width and + is the za beam width. The yagi has a beam width of 16.5 amin az and 17.2 amin za.  The linefeed has a beam width a little less than 10 amin.
• Fig 5: The pointing error measured from the fits. The values are in great circle arcminutes. The top plot is the yagi and the bottom plot is the linefeed. The ch model was used for pointing with great circle offsets of: az: .4833 deg, za: -1.540 deg. The average yagi pointing errors are 2.8 Amin az and -.97 amin za. The pointing errors should be added to the offsets (i had been doing this backwards). Thes  pointing errors say the offsets should have been: az: .53, za: -1.56. The azimuth errors changed by about 2 amin from the 12feb06 measurements. A 2 amin is about 3 inches at the paraxial surface. I don't know how accurately the feed is being remounted each time it is taken down.

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Comparing the 12feb06 and 29may06 data   (top)

• Page 1 top: Gain (K/Jy) for yagi and line feed). The yagi gain on 12feb06 was about 8% higher than 29may06. The carriage house (ch) gains were the same on the 2 days.
• Page1 Bottom: Tsys (K) for the yagi and the line feed. The yagi Tsys on 12feb06 was about 8% higher than 29may06. Both the gain and Tsys being higher on 12feb06 points to the cal value changing  by 8% from the 29may06 value.
• Page 2 Top: Sefd for yagi and ch. The yagi and ch value remained pretty stable on the two days. The yagi sefd may have been a little lower (3%) on 12feb06.
• Page 2 Bottom: The beam widths for the yagi and ch. These remained the same for the two dates.
• Page 3 pointing errors: The + are the az errors while the * are the za errors. The az error for the yagi increased by about 1.5 arcminutes from 12feb06 to 29may06. This is a motion of about 2 inches at the paraxial surface. When the feed was reinstalled 29may06 it was not resurveyed into position.

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Conclusions:  (top)

•     The  comparison between the linefeed and yagi for 29may06 is:

 

	yagi	linefeed
Tsys(za=13)	458	100
gain(za=13)	1.6 K/Jy	13 K/Jy
sefd(za=13) 3C286	295 Jy	9 Jy
beam width	17.5 Amin	9.5 Amin
1st side lobe (db)	az :-9.5 db za: -12 db	az:-12 db za:-14 db
az pnt err (avg) zapnt err (avg)	2.8 amin -1. amin	-.2 Amin -.1  Amin
az pnt offset used: ch pnt offset used	0.4833 deg -1.5483
az pnt offset measured za pnt offset measured	0.530 deg -1.556

• With the new cal values the Tsys for the yagi is 458 K and relatively flat with za.
• Fixing the capacitor did not change the Tsys, gain, or sefd appreciably.
• The ratio of gainCh/gainLf at za=13 deg is 9 db.
• The beamwidth ratios beamYagi/beamCh=1.84. Using the ch gain and the square of the beamwidth ratios gives a yagi gain of 3.8 K/Jy. This assumes the sidelobe levels are the same (which they aren't).
• The yagi first sidelobe level is 2db higher than the line feed.
• The azimuth sidelobe level is 2 db higher than the za sidelobe level. I don't quite understand this since I thought the linefeed and yagi illumination is symetrical (unless we have a collimation error in the az direction).
• The pointing error changed from 12feb06 to 29may06 by aout 1.5 amin (2 inches at the paraxial surface). When the feed was replaced on 29may06 it was not surveyed into position.

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