Brief Description:
The project has two phases. In the first phase we wish to fully understand the governing procedures, methods, workings of different components and their role in Radio Telescope by assembling Radio JOVE(Radio Telescope Kit prepared by NASA) and taking observations from it.
In the next phase,we will try to make Radio Telescope from components available locally. The main aim behind the whole project is to understand Radio Telescope and its workings.The telescope will detect and record Radio Frequency from the Sun and Jupiter.
Radio telescope has two main components,Antenna and Receiver.
Antenna captures Radio signals and converts it into electrical voltage. This electronic signal is then sent to Receiver where it is received,detected and converted in a form that we can analyse.
We have successfully assemble the receiver tuned to exactly 20.1 MHz? frequency.Why 20.1 MHz??
The peak of Jupiter signals occur around 10MHz. Still this frequency is not that suitable, as it is very near to Ionospheric cutoff. The best suitable frequencies are in between 18 to 22MHz, as the chances of getting emissions are more. In practice 18.7MHz, 20.1MHz, 22.3MHz are common. The frequencies above 30MHz are not suitable because of less strength. The frequency of 20.1MHz is used for this project, as the probability of getting emission is high. So the entire receiver is designed considering 20.1MHz as the operating frequency.
Radio Receiver:
Radio signals coming from Jupiter which is located 8*10^8 Km away from the earth is very weak.It generates signal of less than 1 millionths of a volt.This receiver is capable to convert them into audio frequency that can be used to drive Headphone or Loud speaker or can be analysed in a computer.
Below is small description of the components used and their role in the circuit.
Radio Frequency Bandpass Filter and Preamplifier.
Interference can alter the signals and these signals must be eliminated. This is done by Band Pass filter which filters the out of band signals and allow only narrow band centered at 20.1 MHz? to pass through it.The signal is very weak yet.To strengthen it we use Preamplifier.The suffix 'Pri' is used because amplifier is located at the very starting point.
Mixer and Local Oscillator
Mixer,as name suggests mixes up two input signals and generates two signals at output. One of which is arithmetic sum and another is arithmetic difference of the two input signal frequency.The later is of our interest.
Here one input signal is taken from the antenna input and another is from the local oscillator.
Local Oscillator generates a sinusoidal voltage wave form at frequency in the vicinity of 20.1MHz.
e.g If suppose the RF signal from antenna is 20.101 MHz? and LO generates 20.1 MHz? then 20.101-20.1=0.001 MHz?,which is audio frequency of 1 kHz.
Low Pass Filter
This filter passes the low frequency (Arithmetic difference) and eliminates high frequency signals (Arithmetic Sum).
Audio Amplifier
Purpose of the audio amplifier following the low-pass filter is to take the very weak audio signals from the mixer and amplify it enough to drive loudspeaker.
Complete process can be summarize in block diagram shown below
The complete circuit is here
We will start constructing antenna from the first week of August.
Acknowledgments
We are very much grateful to Bill Lord,Vice president of Society of Amateur Radio Astronomers (SARA) and our Mentor for the project, for providing full grant for Radio JOVE kit. See Grant letter here: http://picasaweb.google.com/lh/photo/zHud5_AtwbZic8bagaVGtA?feat=directlink
We extend our gratitude to NASA radio JOVE team for helping us to get grant and the kit.
Our thanks due to our Guide Dr. Vipul Kheraj,Asst. Professor,Deptt. of Applied Physics(NIT-Surat) for restless help in building the receiver without which this project would have not been completed.
We are also thankful to Dr. Rathnasree for providing us very much useful material to understand the physics of Receiver and Antenna and also for providing space here on Astronomy Project page.
Useful References
1) http://radiojove.gsfc.nasa.gov/
2) Radio Astronomy by John Kraus
Group Members:
Charitarth Vyas, Akashrup Banerjee, Keyur Goswami, Suresh Kumar, Mihir Patel.
Pictures of Block Diagram and Circuit is taken from the Receiver construction manual provided with RT kit.Construction manual is also available online here: http://radiojove.gsfc.nasa.gov/telescope/construction_manuals.htm