Arecibo Observatory 430-MHz Gregorian Receiver

Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.naic.edu/~astro/RXstatus/430G/430greg.shtml
Äàòà èçìåíåíèÿ: Unknown
Äàòà èíäåêñèðîâàíèÿ: Mon Feb 4 00:54:41 2013
Êîäèðîâêà:
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Arecibo Observatory 430-MHz Gregorian Receiver To leave the frames behind, click here

430-MHz Gregorian

Basic Information

Calibration & Beam Parameters

RFI Situation

Recent Events

Receiver History

Contact Info

1. Basic Information:

Frequency Range (GHz):	422-442 MHz Plot of frequency response can be found here
Name and Number:	430-MHz Gregorian
Measured Sensitivity (K/Jy):	11*
Measured System Temp (K):	50*
Native Polarization:	Dual circular
Beam Size (at 0.430 GHz):	10' x 12'
Available Filters:	10 MHz, 20 MHz and 30 MHz click here
Warnings and Important Notes:	click here

*See calibration info below for a more accurate description of the telescope parameters!

Available Filters
Filter presently installed is 20 MHz; this is what defines the receiver's frequency response indicated above. If requested, we might change the front-end filter for a particular project. There are plans to build a filterbank for this receiver.
Warnings & Important Notes
When observing with this receiver (or any of the following receivers: 430-MHz Carriage House receiver, 327-MHz Gregorian receiver, 610-MHz Gregorian receiver), make sure that the leftmost switch in Rack 9-2 is in the ANT. LLR 300-1200 MHz position. If it is in the LOAD position, you will get power and a normal-looking bandshape, but no signal from the sky. When observing remotely, ask the operator to check the position of this switch.

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2. Calibration & Beam Parameters:

Gain and Tsys

Cal Values

Beam Maps

Polarization

Misc. Info

Gain and Tsys
The plots below represent the variation with zenith angle of the gain of the telescope, of the total system temperature, of the system's equivalent flux density and of the beam size. The SEFD is not very well constrained, it is 4-6 Jy/K at zenith angles less than 15 degrees.

Tsys values include the contribution from the sky (i.e., Tsky is not subtracted out). Detailed information here.
Cal Values
Noise diode 1 (high)
Left: 95.5 K
Right: 102.55 K
Noise diode 1 (low)
Left: 10.03 K
Right: 10.37 K

Noise diode 2 (high)
Left: 93.5 K
Right: 91.03 K
Noise diode 2 (low)
Left: 12.44 K
Right: 11.91 K
Beam Maps
Not available. However, information on the coma parameter, sidelobe strength and beam efficiency can be found here.
Polarization
Full polarization characterization not yet available.
Misc. Info
To see an up-to-date plot of Tsys, just type tsys on your terminal after logging into Arecibo's computer network.

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3. RFI situation:

Very strong RFI at 427 and 432 MHz was seen to affect 430 MHz receivers in both channels since the last week of February 2003 until the start of 2005.
The problem is due to in-band intermodulation products of the carriers of two TV stations (in nearby channels 14 and 22), which have recently increased their transmitting power. Two such products fall within the 430-MHz bandpass, this severely corrupted many 430-MHz radio astronomical observations.
The installation in February 2005 of higher dynamic-range amplifiers and suitable notch filters has largely reduced the problem.

Previous to the appearance of this problem, there were several UNIDENTIFIED radio FREQUENCY INTERFERENCEs, these were located at:
- 426.25 MHz
- 426.60 MHz
- 433.40 MHz
- 434.00 MHz (This can saturate the receiver)

For RFI with known identifications, click here.

NEWS: E-2 Hawkeye airborne radar is no longer operational from Naval Station Roosevelt Roads. E-2 Hawkeye airborne radar, which operated near 430 MHz. This used to completely destroy your observation.

Daily RFI monitoring plots for the past several years from the Observatory "hill-top" monitoring system can be found in binders in either the telescope Control Room or by asking the Arecibo Spectrum Manager.

For the current daily average 430-MHz RFI plot from the Arecibo "hill-top" monitoring system, click here .
For the current frequency v time 430-MHz RFI plot from the Arecibo "hill-top" monitoring system, click here .
For the current frequency v time 430-MHz RFI plot (with band-pass correction) from the Arecibo "hill-top" monitoring system, click here .
For the current daily rms/mean v frequency 430-MHz RFI plot from the Arecibo "hill-top" monitoring system, click here .

The occurrence of RFI versus frequency by month and year since Jan 2001 can be found via the 430 link on this web page.

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4. Recent Events:

receiver log

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5. Receiver History:

This receiver has seen a marked improvement in system temperature over the last few years, which make it competitive with the CH receiver even for observations near the Zenith. Recently, a 20 MHz front-end filter was installed, which will particularly benefit pulsar observations. An even wider front-end filter of 30 MHz was tried, but unfortunately, this increased the amount of RFI in the band very significantly. Installation of a front-end filterbank is imminent.

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6. Contact Info:

For further information on this receiver, please contact Paulo C. Freire at
pfreire (append @naic.edu)

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