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Дата изменения: Wed Mar 20 17:44:08 2002
Дата индексирования: Sat Dec 22 17:12:01 2007
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RECEIVER CHOICE

The majority of the receivers at Arecibo are housed in the new Gregorian Dome. The exceptions are the 47-MHz and 430CH receivers attached to the old Carriage House. As these receivers are not commonly used for spectral line work they will not be discussed here. Detailed information on the Carriage House receivers can be found both on the relevant receivers' web page and in the pulsar observing handbook.

The available Gregorian receivers are listed in Table 1. In most cases, only one receiver will be available which will meet your frequency requirements. (REMEMBER - At present only one receiver can be used at a time.) In a few cases, such as in the L and S bands, more than one receiver may be available which suit your needs. In these cases, you probably want to choose the receiver with the narrowest frequency range which fits your need. Alternatively, you may wish to choose the most sensitive (lowest SEFD - system equivalent flux density) receiver. Conveniently, these two choices often lead to the same receiver (i.e. using the L-narrow over the L-wide, when possible). The most up-to-date information on the receivers can be found on the Arecibo web pages at http://www.naic.edu/$\sim$astro/RXstatus/.

Table 1: Gregorian Receivers

Frequency Range	Receiver Name	Native Pol.	Sensitivity	System
			(K/Jy)	Temp (K)
0.312 - 0.342	327	Dual Linear	5-6	160
0.425 - 0.435	430	Dual Circular		55
0.609 - 0.614	610	Dual Linear	8	130
1.12 - 1.73	L-wide	Dual Linear	8-11	35-40
1.28 - 1.50	L-narrow	Dual Circular$\dag$	08-10	25-30
l .8 - 3.1	S-low	Dual Linear	7	40
2.33 - 2.43	S-Radar	Dual Circular	9-10	25-30
3.85-6.00	C	Dual Circular	4-8	32-34
8.0 - 10.0	X	Dual Circular	1.5-3*	43.48*
$\dag$The L-narrow is circularly polarized only at 1420MHz
and becomes increasingly elliptically polarized away from this frequency.
*Receiver still being calibrated. These numbers are very preliminary.

L-Wide Receiver Options: If you choose to use the L-wide receiver, a number of options not available to the other receivers must be decided. In particular, you must choose your polarization type and r.f. filter.

• Polarization type: The L-wide receiver is a native linear receiver. It can be converted to circular polarization by selecting a quadrature hybrid inserted outside the dewar.

• Filter bank: Bandpass filters available for the L-wide receiver are not adjustable. This means that when you use a filter, be sure it covers the frequency range which you will be observing, and not your rest frequencies. L-wide filter options are: 1120-1220, 1230-1470, 1550-1820, 1100-1800, 1360-1470, 1180-1280 MHz, or no filter at all. Note that more than one filter can be selected at a time, but you should not use filters which overlap in frequency as that will cause ripples in your baseline.

NOTE: A smaller filter bank will soon be available for both the L-Narrow and S-Wide receivers as well.