IHY User Manual 191P4MHz Ver01

8/6/2019 IHY User Manual 191P4MHz Ver01

1/15

Indian Institute of Astrophysics - Public Outreach

A two element radio interferometer for observations of Sun at 191.4

MHz

User manual Version 3Introduction:

International Heliophysical Year (IHY) is an United

Nations program spread over the years 2007 and 2008. The thrust area

is to study the Sun, Earth's magnetosphere and the interplanetary

medium as a coupled system. One of the major components of IHY is the

Public Outreach Education Program through which the knowledge on Helio

spheric Physics would be disseminated to the general public and more

importantly, to inspire the next generation of space scientists who

are still in schools and universities. In this connection, the Indian

Institute of Astrophysics (IIA), Bangalore has initiated several

activities through its Public Outreach (PO) program. One among themis to provide hands on observing experience in radio astronomy to

interested and motivated science and engineering graduate students in

the country by providing necessary antenna and receiver system to

their institutions. The above set up developed by the radio astronomy

group of IIA can be used to observe radio emission from the solar

corona at 191.4 MHz.

Contents of the 'kit':

1. Log periodic Antenna 2 nos.2. RG 8U coaxial cable (50 m length) 4 nos.

3. 1st stage Amplifier + high pass filter 2 nos.

4. 2nd stage stage Amplifier 2 nos.5. Analog receiver 1 no.

6. RF (LC)Filter 191.4 4MHz 2 nos

7. IF Filter 10.7MHz 30KHz 2 nos

8. Digital receiver 1 no.

9. Power supply 1 nos.

10.IHY Data acquisition CD 1 nos.


2/15


BLOCK DIAGRAM OF IHY SYSTEM


3/15


The radio 'kit':

The observing set up consists of two Log periodic antennas tuned

to receive radio frequency (RF) signal at 191.4 MHz. Each antenna

has an independent analog receiver chain for processing theincident RF signal and subsequent down conversion to the

intermediate frequency (IF) using the super heterodyne principle.

Figure 1 shows the block diagram of the antenna and receiver

system. The RF signal incident on each antenna goes through the

following series of operations before it is transmitted to the

receiver building,The filtering of terrestrial AM broadcast and

other spurious interference signals prevalent at low frequencies

using a high pass filter with cut off at 50 MHz. These otherwise

might saturate the amplifier(s) in the receiver chain,1st stage

amplification by about 30 dB gain in a commercial broad band (0.5

500 MHz) amplifier,transmission of the filtered, amplified RFsignal over a distance of about 50 m via RG 8U coaxial cable 2 nd

stage amplification by about 30 dB gain, identical to the 1st

stage,Then transmission of the filtered, amplified RF signal to

the receiver room via RG 8U coaxial cable over a distance of

about 50 m. A total length of 100 m RF cable is used for each

antenna since this helps to place the two antennas well spaced

apart and obtain interference fringes with good contrast. The

signal attenuation in the cable is about 12 dB at 191.4 MHz.

In the receiver room, the RF signal from each antenna is first

passed through a band pass filter of center frequency (fc)=191.4MHz and bandwidth ( f)=6MHz, to minimize the contribution from

interfering signals at other frequencies. The insertion loss in

the filter is about 9 dB at 191.4MHz. The filtered signal is

given to RF amplifier,amplifier gain about 30dB gain. Then mixed

with a local oscillator (LO) signal of frequency 180.7MHz for

down conversion of the RF signal from the antenna to 10.7 MHz (IF

signal).The output of the mixer is passed through a Band pass

filter fc= 10.7 MHz with the bandwidth f = 1 MHz to further

minimize the contribution from spurious signals and then

amplified by about 30dB gain Finally amplified signal is given to

Quadrature,output of quadrature will give 0'(cosine) and90'(sine). The output of the above signal is given to digital

receiver. In that receiver comparing the two signal sampled and

correlated (with the similar signal from the 2nd antenna) in the

digital receiver. The latter has also provision for integrating

the correlated data before passing it on to the computer for

storage.


4/15


1.Block Diagram of Digital Receiver


5/15


Digital correlator board Electronic schematic diagram:


6/15


Log periodic antenna:

In This log periodic Antenna operating range in frequency of 183MHz to

193MHz,over a bandwidth of 10MHz and gain of antenna is 7dB,The

antenna is made of aluminum tubes(Arms)and booms, For this range

frequency operation we have to choose the boom length,arms length andseparation of arms, below table showing the length of Arms and

spacing between the dipole.

Length of Arms Spacing between Dipole

Dipole 1 30.4cm Dipole 1 & Dipole 2 28cm

Dipole 2 33.2cm Dipole 2 & Dipole 3 29.3cm

Dipole 3 36

For any transmitting or receiving antenna we should match the system

impedence,For that we have to measure the VSWR(voltage standing wave

ratio).it is ratio of maximum voltage to minimun voltage along the

transmission line.For measuring VSWR we have to use spectrum

analyzer.below diagram showing the VSWR of the (183MHz to

193MHz)logperiodic antenna. For better signal VSWR should be less than

2 and return loss should be more.


7/15


Measurement :

RF FILTER(TUBULAR) OUTPUT:

PARAMETERS EAST SIDE WEST SIDE

Centre Frequency 191.4MHz 191.4MHz

Insertion Loss 9dB 9dB

3 dB Bandwidth 6MHz 6MHz

Frequency and Level @191.4MHz and -55dBm @191.4MHz and -56.5dBm

RMS voltage 3.2mv 2.6mv

RF AMPLIFIER(MAN) OUTPUT:


Gain of the Amplifier +30dBm +30dBm


RMS voltage 50mv 94.5mv

VSWR 1.5 1.5


8/15


RF MIXER(SBL)OUTPUT:




RMS voltage 67mv 34mv

LO OUTPUT:


Frequency and Level @180.7MHz and +8dBm @180.7MHz and +8dBm

IF FILTER(TRILITHIC)OUTPUT:


Centre Frequency 10.7MHz 10.7MHz


3 dB Bandwidth 1MHz 1MHz

Frequency and Level @10.7MHz and -32dBm @75MHz and -35dBm


IF AMPLIFIER(MAN) OUTPUT:


Gain of the Amplifier +28dBm +28dBm

Frequency and Level @10.7MHz and -5.5dBm @10.7MHz and -7dBm


VSWR 1.5 1.5

IF QUADRATURE(PSCQ):



Frequency and Level @10.7MHz and -8.5dBm @10.7MHz and -10dBm



9/15


Installation

System requirements:

Desktop or Laptop with Microsoft windows XP(P III,IV).

Please maintain the screen resolution 1280X1024 or maintain

maximum resolution.

USB port.

How to install the system

1. Mount the two log periodic antennas separated by a distance ofabout 50 80 m, depending on the distance to the receiver room and

the available length of RG 8U cable.

2. Connect 15 V power supply to the amplifiers near the antenna end

as well as in the receiver room.

3. Connect the 1st stage amplifiers to the output from the twoantennas.

4. Take two nos. of 25 m length of RG 8U cable and connect the

output of the above two amplifiers to one end of each of them.

5. Connect the input of the two 2nd stage amplifiers to the otherend of the aforementioned two RG 8U cables.

6. Connect the output of the two 2nd stage amplifiers to the inputof the analog receiver unit in the receiver room using the

remaining two nos. of 50 m length of RG 8U cables.

7. Connect the two IF outputs from the analog receiver to thedigital receiver.

8. Connect 5 & 5 V power supply to the digital receiver.

Connect the output of the digital receiver to the USB port of the

Laptop/Desktop using the interface cable.

Hardware Installation procedure :

The DAQ Software installation program consists of a series of easy to

follow dialogs that lead you through the installation procedure. To

install the Measurement Computing DAQ software, do the following.

Insert the Measurement Computing Data Acquisition Software CD in your

CD drive and wait for the installation program to start.

If the installation program does not start automatically, use

Windows Explorer to browse to the root of the CD, and

double click on and follow the following steps:


10/15


The MCC DAQ dialog opens.

Then press INSTALL

Then press NEXT and follow it.


11/15


Then press INSTALL to install the program.

Running InstaCal and adding

your hardware

This section explains how to run InstaCal and add the USB BOARD

to the InstaCal configuration.

1. To run InstaCal, click on Start All Programs Measurement

Computing InstaCal .

InstaCal's main form opens.

Then automatically a window appears like bellow

click ok to add the USB board.


12/15


If instacall doesn't start automatically then please follow the

following procedure to add board:

2. Click the right mouse button on the PC Board List, and selectAdd

Board from the pop up menu.

The Board Selection List dialog opens.

Running InstaCal and adding your hardware

3. Click on the USB tab.

4. Scroll down to select USB BOARD , and then click on theAdd

button.The USB BOARD is added to InstaCal's main form.

Now that you have added the USB BOARD you can use this form to

configure and test the USB BOARD.

Installing the data acquisition software:

Double click setup.Exe file from the acquisition CD and follow the

instructions to install data acquisition software...

Then please follow the pop up instructions to install...


13/15


How to start the IHY data acquisition:

1) After successfully installing IHY Data acquisition software CD

an IHY icon will appear on the desktop automatically.

2) Check all the power supply is on.

3) Double click the IHY icon to start data acquisition.

4) The initialization screen will appear on the screen as shown

below.

5)Choose the appropriate source and the observation time in hrs and

then press OK to start acquisition as shown below.


14/15


6) The Data acquisition screen will appear on the screen asshown above.

Data Storage & File name format:

1) User can choose the Directory where data can be stored as

mentioned above.

2) In that directory a folder named IHY will be created

automatically where the observed data files will be saved.

3) The file name format and example is as given below

Format :IHYyyyymmddHHMMSS.source

Example :IHY20080817035932.SUN

extension of the file name represents the first three characters

of the observed source name.


15/15


Tips & Hints:

1) Restart computer after installation of the software.

2) Check the power supply connections before the system is switched

'ON' for observations.

3) It is always better to carry out a trial run every day for a few

minutes before commencing the regular observation.

4) Ensure that the power supply (both AC as well as DC) is 'OFF'

while checking the analog and digital components in the system.

5) Please disable anti virus , screen savers, power mode, automatic

updates etc... in the computer that is used for data acquisition.

They might disturb the observations.

6) Avoid running other applications in the data acquisition computer

(either in the background or foreground) while the observation is

'ON'.

7) Avoid seepage of rain water inside the 1st and 2nd stage RF

amplifiers which will be out there in the 'field'. Keep them in a

dry environment and at a height of about two feet from the

ground.

8) Carry out observations everyday between 10 AM (START) 3 PM

(END), to the maximum possible extent.

9) The raw data will be stored in ASCII format in the computer hard

disk. It can be plotted either using MATLAB or MS EXCEL software

or any other graphics routine.

Some of the quantitative results that can be obtained upon analysis of

the data obtained are:

A comparision of the daily fringe amplitude (particularly when

the Sun is 'undisturbed', I.e when there is no solar flare

activity) for a period of time will give information on the

variation in the radio emission from the background solar corona

at 191.4MHz and the appearance/disappearance of discrete

structures in the solar atmosphere like coronal holes, streamers,

etc.

An estimation of the angular separation between the adjacent

fringes give information the baseline separation between the two

antennas. Note that the fringe separation is proportional to d

radians, where 'd' is the baseline separation between the

antennas and '' is the wavelength of observation.

Radio burst emission data obtained during a solar flare/coronal

mass ejection can be analyzed to obtain information on plasma

parameters of the associated region in the solar atmosphere.

Date post:	07-Apr-2018
Category:	Documents
Upload:	lokesh-pimpale
View:	226 times
Download:	0 times

IHY User Manual 191P4MHz Ver01

Documents