EVLA Frequency Bands and Tunability

The EVLA electronics and local-oscillator systems enable tuning over wider frequencies, which is possible with the wideband feeds being installed on retrofitted antennas (or already present at K and Q bands). In 2007, there will be enough EVLA antennas available to enable the first observations to make use of this wideband tuning capability, and we also will begin equipping EVLA antennas with new receiver systems at Ka band ($\lambda$ 1.0 cm). For example, the new C band tuning will enable observations of methanol at 6.7 GHz, while the new K band tuning will enable observations of the 22.235 GHz H$_2$O line at redshifts $z=0.1$ to $z\approx 0.18$. Figure 3 shows the present plan for EVLA receiver deployment over the remainder of the EVLA Construction Project, while Table 5 gives a prediction of the new frequency capabilities that we expect in June 2007 and December 2007.

Figure 3: EVLA Receiver Deployment Plan. Above are plots of planned deployment schedule for the EVLA receivers until the end of the EVLA Construction Project in 2012. The eight EVLA bands are listed in separate plots, with observing frequency increasing from upper left to lower right. The decreasing red lines indicate old VLA receiver systems. The light blue lines indicate transition EVLA receivers; in the case of L, C, and X bands, these receivers have the old VLA frequency coverage rather than the more expanded EVLA frequency coverage. The green lines indicate the numbers of final EVLA receivers, and the dark blue lines indicate the total numbers of receivers. (Note that the dark blue and green lines overlap completely for the new S and Ka bands.) The vertical dashed line (in purple) indicates the beginning of 2008, after which the prototype EVLA correlator will begin to appear. Finally, the diagonal dashed line (in black), identical for each band, gives the total number of EVLA antennas that will be outfitted as a function of time. Approximate frequency coverage of the final EVLA receivers is indicated below in Table 5.

Table 5: Tuning Ranges of EVLA Bands

Band	Range	No. EVLA Antennas Available
		June 2007	December 2007
20 cm (L)	1.2 - 2.0 GHz	2	3
13 cm (S)	2.0 - 4.0 GHz	0	0
6 cm (C)	4.0 - 8.0 GHz	1	2
3 cm (X)	8.0 - 12.0 GHz	0	0
2 cm (U)	12.0 - 18.0 GHz	0	0
1.3 cm (K)	18.0 - 26.5 GHz	7	11
1 cm (Ka)	26.5 - 40.0 GHz	4	9
0.7 cm (Q)	40.0 - 50.0 GHz	7	11