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430 MHz Carriage House Receiver
Basic Information

Calibration & Beam Parameters

RFI Situation

Recent Events

Receiver History

Contact Info




1. Basic Information:

 

Frequency Range (GHz): 0.425-0.435

Name and Number:

430ch (Rx no. 100)
Measured Sensitivity (K/Jy): 20 (*)
Measured System Temp (K): ~120 (including sky)(*)
Native Polarization: Dual Circular
Beam Size (at 0.430 GHz): 9.5 x 8.5 sq. arcminutes
Available Filters: 10 MHz centered at 430 MHz
Warnings and Important Notes: click here

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

 

2. Calibration & Beam Parameters:


Gain and Tsys Cal Values Beam Maps Polarization Misc. Info


 

3. RFI situation:

  • TV station intermods
    Very strong RFI at 427 and 432 MHz was seen to affect the two 430 MHz receivers in both channels since the last week of February 2003 until February 2005, when the problem was solved (see below). The problem was due to in-band intermodulation products of the carriers of two TV stations (in nearby channels 14 and 22). Two such products fall within the 430-MHz bandpass, and this has severely corrupted many 430-MHz radio astronomical observations.

    Attempts were made during the first week of May 2003 to resolve this problem by adding a bandpass cavity filter offering more attenuation at the carrier frequencies as well as by replacing then existing amplifiers with ones with larger dynamic range. Subsequent tests and azimuth scans revealed that this in-band RFI was still present and was particularly strong in certain azimuth ranges (with a peak around 120 deg. azimuth). See above link for more details.

    A low loss bandpass filter with notches at 475 and 520 Mhz was placed in front of the gregorian dewar for polA at the beginning of October 2004 (see details here). This knocks down the TV station signals to a level that they will not create intermods in the dewar. The filter has effectively removed the intermods. Similar filters have been installed in February 2005 on the 430 MHz CH receiver (both polarizations).

  • Previous to the appearance of this problem, there were several UNIDENTIFIED RFIs, located at:
    - 426.25 MHz
    - 426.60 MHz
    - 433.40 MHz
    - 434.00 MHz (This can saturate the receiver).

  • For a list of 430 MHZ BIRDIES, click here.
    For RFI with known identifications, click here.

  • Hawkeye airborne radar
    The E-2 Hawkeye airborne radar is no longer operational as of June 2004. There used to be a broad (6 MHz) pulsed signal (period 10 or 12 seconds) caused by the Atlantic Fleet and Weapons Training Facilities (AFWTF) Hawkeye airborne radar, which operated near 430 MHz. This used to completely destroy your observation.

  • To find out more about RFI at this site, look at Phil Perillat's and the RFI sites.

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4. Recent Events:

For updated info on the maintenance of this receiver, look at the electronics department receiver log.

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5. Receiver History:

This is one of the oldest receivers still operating at the Arecibo radio telescope, and it is still the one that provides the largest gain. The problem of such a wide illumination pattern is that away from zenith, the receiver illuminates a lot of the 300 K ground, causing a large drop in gain and a steep increase in system temperatures. While the problem with decreasing gain cannot be dealt with (unless the primary surface is expanded...), the introduction of a ground shield during the recent Arecibo upgrade should have improved the situation of the Tsys for pointings away from the zenith. The plot below is from a calibration made in 1989. It shows that the gain curves have not changed much, as expected, since the main reflector retains its size. The degradation for zenith angles near 20 degrees compared to zenith is smaller in 2001 than in 1989, here we can see the improvement caused by the ground screen.
A description/log of this receiver history/problems/etc. can be found here.

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6. Contact Info:

For further information on this receiver, please contact Aaron Parsons at
aparsons (append @naic.edu)

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