Introduction

A brief technical summary of the Thoth Technology 46 m antenna on the site of the Algonquin Radio Observatory (ARO) in the Province of Ontario, Canada is provided.

Location

The antenna is located at 45 deg 57 min 19.8 sec latitude, 281 deg 55 min 37.0 sec east longitude, 260.4 m elevation.

Antenna Performance

The following table presents the estimated performance information for the 46 m antenna at ARO.
Table 1 Antenna Performance, 46 m Antenna at ARO

Aperture efficiency 0.42 at 10 GHz (full surface); 0.29 at 22 GHz
(inner solid surface)
Area gain 74 dBi at 10 GHz
Effective aperture gain 70 dBi at 10 GHz, 69.1 dBi at X-band, 68.6 dBi
at S-band

RF/IF Specifications

  • (a) Hydrogen maser time and frequency reference: frequency stability 1014 to 1015
  • (b) Dual frequency S- and X-band front end receivers with concentric LCP feeds for simultaneous S- and X-band observations. L-band capability.
  • (c) Closed cycle helium cooling system for front end receivers.
  • (d) System temperatures approximately 55 deg K for X-band and 60 deg K for S-band
  • (e) S-band IF i. S-Band first LO is 2020 MHz ii. Maximum receiver noise power density: -44 dBm Hz-1 at 191 MHz iii. –3 dB points at 173 MHz and 283 MHz
    iv. –10 dB points at 132 MHz and 437 MHz v. –20 dB points at 132 MHz and
    462 MHz vi. Linear portion of passband from 191 MHz to 425 MHz
  • (f) X-Band IF i. X-Band first LO is 8080 MHz ii. Maximum receiver noise power density: -49 dBm Hz-1 at 152 MHz iii. -3dB points at 83 MHz and 317 MHz iv. -10dB
    points at 60 MHz and 613 MHz v. -20dB points at 37 MHz and 920 MHz vi. Linear portion of passband from 132 MHz to 902 MHz
  • (g) L-Band IF i. L-Band
    first Local Oscillator is 1010 MHz ii. Receiver Noise Temperature 0.78
    COLD, 2.983 HOT. iii. IF output frequency 285 MHz, 110 MHz bandwidth (3 dB)
    iv. LNA noise temperature 31 degree K and gain of 39 dB. v. Passband 1150
    to 1750 MHz
  • (h) VLBI data acquisition system backend. Dual Frequency X- and
    S-band operation with USB and LSB outputs for both RF channels. Baseband
    bandwidths variable from 250 kHz to 16 MHz. 1- and 2-bit sampling and
    recording.
  • (i) GPS active control point (location reference station).

The Antenna Structure

The following table presents information on the structure of the 46 m antenna.

Table 2 Antenna Structure, 46 m Antenna at ARO

Antenna diameter 150 feet (45.8 m)
Focal length Prime focus 60 feet (18.3 m)
Parabolic reflector Inner surface of 0.635 cm (1/4 in) thick steel plate, 36.6
m (120 feet) in diameter. Outer surface of panels of galvanized
steel square mesh of 1 mm diameter wire with 10 mm spacing,
4.55 m (15 feet) in radius width all round. The solid surface
is adjustable with one adjuster screw at every 4-corner
intersection of the steel plates
Focii Both prime focus and Gregorian capability with 10 foot
(3 m) diameter elliptical subreflector
Focal ratio F/D = 0.4 for full surface and F/D = 0.5 for inner solid
surface
Feed support Tetrapod feed legs supporting prime focus aerial cabin.
Prime focus cabin: cylindrical 2.5 m diameter by 3.7 m
length
Gregorian focus Located in the Vertex Room: cylindrical 5.8 m diameter
by 6.4 length
Surface accuracy rms departure from best fitting paraboloid = 0.85 mm.
Maximum departure from best fitting paraboloid = ±0.32 mm
(inner solid surface) = ±0.64 mm (outer mesh
surface)

Antenna Operations and Control

The following table presents operations and control information for the 46 m antenna at ARO. Table 3 Operations and Control, 46 m antenna at ARO

Altitude/Azimuth antenna mount Computer controlled pointing
Azimuth range of motion ±215 degrees in Azimuth centred on an Azimuth of 112.5
degrees West of North
Elevation range of motion 102 degrees (-5 degrees to 97 degrees) in elevation
Maximum operating wind velocity 80 kmhr-1 (50 mph)
Extreme operational temperature range -46oC to +40oC
Azimuth slewing Variable in rate up to 24 degrees per minute
Elevation slewing Variable in rate up to 10 degrees per minute ascending
and up to 15 degrees per minute descending
Pointing accuracy Current performance ±20 arc sec. With enhanced pointing
model in place ±10 arc sec