Multibeam Receiver Description

The Parkes 21cm Multibeam Receiver is a new facility available on the Parkes Telescope which is operated by the Australia Telescope National Facility (ATNF), CSIRO. The facility consists of a 13-beam cooled 21cm receiver system, located at the prime focus of the 64m dish. The hexagonal feed cluster is designed by the CSIRO Division of Telecommunications and Industrial Physics. The receiver was built as a collaboration between: the ATNF; the Universities of Melbourne, Sydney, Western Sydney and Cardiff; Mount Stromlo and Siding Spring Observatories; and Jodrell Bank with funding provided by the ARC and the ATNF.

Completed 21cm Multibeam Receiver being hoisted up to the Parkes focus cabin.

The receiver was funded to conduct the HIPASS ("HI Parkes All-Sky Survey" ) and ZOA (Zone of Avoidance) HI surveys. It is now available, in 64 MHz mode and in pulsar mode, for normal National Facility use. Narrow band 4, 8 and 16 MHz filters are available.

PASA paper (vol 13, p 243, 1996) giving overview of multibeam receiver

Receiver Specifications

The multibeam receiver was designed to have high performance for 21cm line work. This was achieved by compromising performance in other areas such as frequency range and polarisation purity. The following table lists the receiver specifications.

Parameter Beam 1Beams 2-7Beams 8-13
Frequency Range 1.23-1.53 GHz 1.22-1.52 GHz 1.22-1.52 GHz
Polarisations 2 orthogonal linear 2 orthogonal linear 2 orthogonal linear
Average System Temperature (K)
21 K 21 K 21 K
FWHP beamwidth 14.0 arcmin 14.1 arcmin 14.5 arcmin
FWHP beam ellipticity (radial) 0.00 0.03 0.06
Efficiency 1.36 Jy K-1 1.45 Jy K-1 1.72 Jy K-1
Average System Temperature (Jy)
29 Jy 30 Jy 36 Jy
Average Cal Temperature (Jy) 1.6 Jy 1.8 Jy 2.0 Jy
Coma lobe none -17 dB-14 dB


(1) System temperature reaches a minimum at an elevation of about 55o. At extreme elevations (30o and 90o), temperatures are about 2 K higher. Temperatures are measured at a frequency of 1394.5 MHz over a bandwidth of 64 MHz.

(2) The flux density scale is based on Hydra A for which a value of 40.6 Jy at 1394.5 MHz is assumed (after accounting for an 8% beam dilution; Reynolds, private communication).

Feed Configuration

The above diagram shows the configuration of the feed system as projected onto the sky when the feed angle is 0o and the telescope is observing on the northern meridian. North is to the top, east to the left. The available range of feed angles range from -60o to +60o. When the feed angle is 0o, beam 3 is closest to the lift leg which lies on the downhill side of the prime focus cabin.

Normally, the multibeam receiver is used to map extended areas. Typically the feed angle is set to 15o to the scanning angle. The scanning rate is usually around 1o min-1. Scans are normally made in "stepped" mode, where the parallactic angle is only correct at mid-scan. This is to avoid problems with the changing bandpass as the receiver rotates. However, full parallactification may be enabled if required.


The multibeam receiver is normally used with the multibeam correlator which is based on the Canares chip. However, the central beam may also be used with the Parkes AT correlator (not simultaneously) if higher frequency resolution is needed. A pulsar backend is also available. Presently, only the 64 MHz bandwidth mode is available from the multibeam correlator.

Parameter64 MHz8 MHz4 MHz
Number of beams 13 7 7
Number of polarisations/beam 2 2,4 2,4
Maximum number of channels/polarisation 1024 2048 2048
Corresponding channel separation (kHz) 62.5 3.91 1.95
Frequency resolution (kHz) 75.6 4.73 2.36
Velocity resolution (km s-1) 16.0 1.00 0.50
..with Tukey 25% smoothing (km s-1) 18.0 1.12 0.56
..with Hanning smoothing (km s-1) 26.4 1.65 0.82
..with Tukey 25% + Hanning smoothing (km s-1) 27.0 1.69 0.85


(1) Tukey 25% smoothing is recommended in 64 MHz mode to suppress ringing from Galactic HI. LiveData is able to perform this.

(2) The FWHM (50%) resolutions are 1.21, 1.36, 2.00 and 2.05 times the channel spacing for sinc, Tukey 25%, Hanning and combined Tukey+Hanning weighting, respectively. For the 20% level, multiply the channel spacing by 1.64, 1.88, 2.88 and 2.90, respectively. Calculations by Tom Oosterloo.

(3) Limited capablility is available for XY/YX cross-correlation and cross-correlation between beams. Contact Warwick Wilson ( for details.

Pulsar backend

See the pulsar web pages for details.

Created by: Lister Staveley-Smith - 27. May 1997
Updated by: Baerbel Koribalski - 26. March 2010