Transcript An Inexpensive Radio Telescope

A Radio Telescope
for High School
Education
Abe Reddy
North Dakota State University, Department of Physics
Advisor: Professor Brian Keating, UCSD CASS
UCSD Physics REU, Sponsored by NSF
Outline
 Radio Astronomy and Radio Telescopes
 SRT Design
 SRT Capabilities
Radio Astronomy
 Radio vs. Optical
 Less 1mm to several meters/400-700nm
Radio Telescopes
 Larger than optical
 Angular resolution
proportional to λ/D
 Prime Focus vs.
Cassegrain
Reflectors
 Reflector,
Subreflector,
feed/horn, receiver
Overview
 Made From Commercially Available Parts
 Capable of receiving signals at 3 &12
GHz, simultaneously
 Freeware Software Interface written in
Java
Antenna
Antenna Mount
 Motors for Azimuth and Elevation angles
 0.1 degree pointing resolution
 Reed Sensor
 12 pole magnet
 11.7 counts/degree
 Counts are sent to Controller Box
Receiver Design
 Orthomode Transducer
 Splits EM waves into orthogonal
components
 Low Noise Block Downconverters
 High Electron Mobility Transistor
Amplifier
 Increases the signal amplitude
 Mixer
 HEMT output and reference signal
 Heterodyne downconversion to reduce
frequency
 IF Amplifier
 Amplifies signal again
 Passes signal through shielded coax cable
 Bias-T Circuit
 Removes AC signal component
 Passed through total power detector then
amplified again
 Low-Pass Filter
 Removes High-Frequency Interference
 Voltage to Frequency Converter
 Converts Voltage to pulses
 Stamp Microcontroller
 Determines frequency of pulses
 Communicates with computer
Software Interface
 Displays map of the sky
 Displays power output for all 4 channels
 Graphs power vs. time
 Outputs contour plot for 25 point scans
Data Analysis
 Azimuth Scans
 Equivalent
Blackbody Temp
 Polarization
Outlook
 Usage as a Polarimeter
 Data Analysis
 Pointing Corrections
 Lab Courses