L-band comparison

(08/21/01 J. Hibbard)

EVLA Cassegrain and Prime focus performance numbers taken from memo "Electromagnetic Analysis of the VLA Antennas at L-band" by S. Srikanth, dated 20 May 1999. The Cassegrain system refers to the smaller 1.5GHz feed design (length 186", diameter 76"), which has poorer performance above 1.4 GHz (but has the advantage of not protruding beneath the vertex room floor).

Efficiency Trade

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 0.63

700 MHz 1.03 - 0.54 -

800 MHz 0.78 0.23 0.49 -

900 MHz 0.58 0.46 0.43 0.38??

1000 MHz 0.42 0.49 0.34 0.38

1100 MHz 0.29 0.53 0.33 0.38

Effective Area Trade

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 30000 m²

700 MHz 1.03 - 7160 m² -

800 MHz 0.78 3050 m² 6500 m² -

900 MHz 0.58 6100 m² 5700 m² 18000 m² ??

1000 MHz 0.42 6500 m² 4500 m² 18000 m²

1100 MHz 0.29 7025 m² 4375 m² 18000 m²

Tsys Trade Study (elevation=60deg)

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 100 K

700 MHz 1.03 - 32 K -

800 MHz 0.78 52 K 25 K -

900 MHz 0.58 33 K 19 K 70 K ??

1000 MHz 0.42 32 K 15 K 70 K

1100 MHz 0.29 29 K 15 K 70 K

Noise Trade Study (elevation=60deg)

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 1.2 mJy/MHz/min

700 MHz 1.03 - 2.1 mJy/MHz/min -

800 MHz 0.78 6.4 mJy/MHz/min 1.8 mJy/MHz/min -

900 MHz 0.58 2.0 mJy/MHz/min 1.6 mJy/MHz/min 1.2 mJy/MHz/min ??

1000 MHz 0.42 1.8 mJy/MHz/min 1.6 mJy/MHz/min 1.2 mJy/MHz/min

1100 MHz 0.29 1.6 mJy/MHz/min 1.6 mJy/MHz/min 1.2 mJy/MHz/min

Number of Galaxies Detected in 400 hrs (dW=150 km/s, S/N=5)

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 0

700 MHz 1.03 - 1 -

800 MHz 0.78 0 46 -

900 MHz 0.58 69 286 2??

1000 MHz 0.42 241 482 27

1100 MHz 0.29 413 507 56

Number of Galaxies Detected in 2700 hrs (dW=150 km/s, S/N=5 over line)

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 0

700 MHz 1.03 - 200 -

800 MHz 0.78 2 936 -

900 MHz 0.58 767 1631 70??

1000 MHz 0.42 1027 1550 183

1100 MHz 0.29 1004 1150 186

Number of Galaxies Detected in 2700 hrs (dW=150 km/s, S/N=10 over line)

Frequency Redshift EVLA Cass Focus EVLA Prime Focus GMRT

600 MHz 1.37 - - 0

700 MHz 1.03 - 6 -

800 MHz 0.78 0 132 -

900 MHz 0.58 158 514 7??

1000 MHz 0.42 390 706 53

1100 MHz 0.29 548 656 83

John Hibbard

Last modified: Thu Mar 27 15:14:28 EST 2003

Efficiency Trade
Frequency	Redshift	EVLA Cass Focus	EVLA Prime Focus	GMRT
600 MHz	1.37	-	-	0.63
700 MHz	1.03	-	0.54	-
800 MHz	0.78	0.23	0.49	-
900 MHz	0.58	0.46	0.43	0.38??
1000 MHz	0.42	0.49	0.34	0.38
1100 MHz	0.29	0.53	0.33	0.38

Effective Area Trade
Frequency	Redshift	EVLA Cass Focus	EVLA Prime Focus	GMRT
600 MHz	1.37	-	-	30000 m²
700 MHz	1.03	-	7160 m²	-
800 MHz	0.78	3050 m²	6500 m²	-
900 MHz	0.58	6100 m²	5700 m²	18000 m² ??
1000 MHz	0.42	6500 m²	4500 m²	18000 m²
1100 MHz	0.29	7025 m²	4375 m²	18000 m²

Tsys Trade Study (elevation=60deg)
Frequency	Redshift	EVLA Cass Focus	EVLA Prime Focus	GMRT
600 MHz	1.37	-	-	100 K
700 MHz	1.03	-	32 K	-
800 MHz	0.78	52 K	25 K	-
900 MHz	0.58	33 K	19 K	70 K ??
1000 MHz	0.42	32 K	15 K	70 K
1100 MHz	0.29	29 K	15 K	70 K

Noise Trade Study (elevation=60deg)
Frequency	Redshift	EVLA Cass Focus	EVLA Prime Focus	GMRT
600 MHz	1.37	-	-	1.2 mJy/MHz/min
700 MHz	1.03	-	2.1 mJy/MHz/min	-
800 MHz	0.78	6.4 mJy/MHz/min	1.8 mJy/MHz/min	-
900 MHz	0.58	2.0 mJy/MHz/min	1.6 mJy/MHz/min	1.2 mJy/MHz/min ??
1000 MHz	0.42	1.8 mJy/MHz/min	1.6 mJy/MHz/min	1.2 mJy/MHz/min
1100 MHz	0.29	1.6 mJy/MHz/min	1.6 mJy/MHz/min	1.2 mJy/MHz/min