EEEN 4224 - EEWeb Communitys.eeweb.com/.../22/Technical-Report_4_20_11-1303495812.docx · Web viewThe loops are constructed from soft copper tube, and joined at the corners with 90

EEEN 4224

ECE Project Lab

Technical Report

Home Weather Satellite Receiver Station

Christopher DulavitzCarlos PerezJesus Reyes

Spring 2011

Texas A&M University – Kingsville, Electrical Engineering and Computer Science Department

ACKNOWLEDGEMENT

We are grateful to all the people who encouraged us to select this topic for our

senior project design. Nearly all of the work that is ahead of us will be related to many of

the previously taken courses in Electrical Engineering. Many challenges are ahead of us,

but we are confident that we will archive our goal. We are also thankful to the following

group of people: our project advisor Dr. Claudio Montiel, he will be our guide during the

coming months, our senior design instructor Dr. Chung Leung, Mr. Carlos Hinojosa, the

machinist who helped us with project construction, and all the Electrical Engineering

Faculty that will contribute with the development of project.

We would especially like to thank our parents, friends whom supported us

throughout our lives. Without their support for all of these years, we would have never

made it this far. Thank you.

Texas A&M University – Kingsville, Electrical Engineering and Computer Science Department 2

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENT ……………………………………………….. 2

TABLE OF CONTENTS ………………………………………………… 3

LIST OF FIGURES ……………………………………………………… 5

LIST OF TABLES …………………..…………………………………… 6

I. INTRODUCTION ……………………………………………….. 7

1.1 Objective ……………………………………………… 7

1.2 Background ……………………………………………… 8

1.3 Scope ……………………………………………… 9

II. DISCUSSION ……………………………………………… 10

2.1 Approach ………………………………………………….. 10

2.2 Statement of Work ……………………………………… 28

III. RESOURCES ..…………………………………………………… 29

3.1 Personnel ………………..………………………………… 29

3.2 Facilities and Equipment ………………………………….. 29

IV. COSTS ..………………………………………………….……….. 30

4.1 Budget …………………………………………………….. 30

4.2 Timeline …………………………………………………… 31

V. DATA ANALYSIS ….………………….………………………… 32

5.1 Procedure ………………………………………………….. 32

5.2 Data ……………………………………………………….. 32

5.3 Interpretation ……………………………………………… 34


VI. CONCLUSION …………………………………………………… 35

REFERENCES ..…………………………………………………………... 36


LIST OF FIGURES

Figure Page

1. Quadrifilar Helix (QFH) Antenna and Four-turn Balun ……........... 11

2. Quadrifilar Helix Antenna with Dimensions ………………….…... 12

3. Coaxial Connections on top of Mast …………………………..….. 13

4. Bending the Small Loop ……………………..…………..…….….. 14

5. Basic FM Receiver Block Diagram …….……………………...….. 16

6. Phase-locked loop (PLL) block diagram ………………………….. 17

7. First Press bit stream and Subsequent Press bit stream…………….. 20

8. Circuit for Voltage Divider…………….…………………………… 21

9. Transmitting an ASCII minus “-“sign……………………………… 25

10. Home Weather Satellite Receiver Station……………………….… 28

11. Project Timeline …………………………………………………… 31

12. NOAA Satellite Image on 2-28-11 ………………………………… 33

13. Resonance Frequency of Antenna………………………………….. 34


LIST OF TABLES

Table Page

1. Pin Functions of HM-98 ..….………………………………….. 18

2. Waveforms Sent by HM-98 Hand Microphone ……………….. 19

3. Components List and Cost …………………………………….. 30


I. INTRODUCTION

1.1 Objective

The development, design, and construction of a fully functional home weather

satellite receiver station will be attempted. The objective is to get weather images

broadcasted by American NOAA and Russian Meteor satellites for which, the

development of system composed of an antenna with a very high gain, and a receiver

capable of processing signals in the range of 137 MHz will be required.

The signals from the NOAA weather satellites are transmitted with right-hand

circular polarization. There are two common solutions to this problem, the crossed dipole

and the quadrifilar helix (QFH) antenna. The antenna will be designed to capture the

operating frequencies of NOAA and Russian Meteor satellites; in addition the antenna

has to work with the receiver. In the same way, NOAA satellites transmit radio

frequencies that range from 137 to 138 MHz. In order to acquire these signals, a modified

FM receiver has to be employed. The receiver must have the capability to tune to these

frequencies. The most popular means of decoding weather satellite transmissions and

creating images these days is accomplished by means of a personal computer (PC) and a

soundcard. The soundcard is the A/D demodulating interface, while appropriate image

display software on the PC is used to view the images.

To be able to tune to the correct signal frequency, it is necessary to track the

desired satellite. There is an extensive list of free software packages that would facilitate

the tracking of these satellites. Likewise, freeware is also available to decode the signal

received from the satellite into images that will be displayed on the PC monitor


1.2 Background

Weather satellites can generally be categorized as Low Earth Orbiters (LEO).

These satellites typically follow an orbit of a few hundred to a couple of thousand

kilometers in altitude. They constantly move relative to the earth’s surface so are close

enough to obtain sharp pictures of what they see below them. The LEO weather satellites

orbit from pole to pole, which allows them to pass over most areas on earth at least once

within a given time.

The US National Oceanographic and Atmospheric Administration (NOAA)

operate both Geostationary Orbits (GEO) and Low Earth Orbiter (LEO) polar satellites.

The NOAA polar satellites orbit at 850 km and pass within view of all areas on earth at

least twice a day. The satellite carries a number of instruments including cameras for both

visible and infrared light [1].

The cameras scan back and forth at right angles to the ground path, like a broom

sweeping side-to-side as you walk forward, taking picture strips that cover an area 3,000

km wide. The satellite thus makes a continuous picture as if it was a tape reeling out from

an endless roll.

The image, however, is not recorded on the satellite. Each image strip is

immediately broadcast to the ground at a frequency just above 137 MHz, and the satellite

will be in range for up to 12 minutes as the satellite passes from horizon to horizon.

The broadcast uses the Automatic Picture Transmission (APT) analog format for

the imagery. Currently, there are 6 operational NOAA polar orbiters but usually only two


or three have the APT activated at a given time. The Russian Meteor series of satellites

also broadcast with the APT format.

Our goal is to capture the APT broadcasts from NOAA and Russian Meteor

satellites in hopes of decoding them to recreate the image seen by the satellites.

1.3 Scope

There are several limitations related to this project. For one, the receiver we are

using cannot be easily interfaced with a PC. We will instead interface the receiver with a

microcontroller such as the MiniDragon+, which will be programmed and controlled

using the PC. By using a PC and microcontroller to interface with the receiver, we can

control the automation of the receiver ourselves by writing a program to do so. Also,

because the antenna will be mounted outdoors, measures will be taken to prevent any

damage that may occur to it, the receiver, PC, and any other devices.


II. DISCUSSION

2.1 Approach

The first item on the agenda is to order and obtain all the parts required to make

the project before the semester begins. After we have obtained everything we need, the

antenna will be built.

Satellite broadcasts are around 5 W, thus somewhat weak requiring a high-gain

antenna for reception. The antenna we have chosen for the project is a quadrifilar helix

(QFH) antenna because they are said to receive a good satellite signal from horizon to

horizon. These antennas are made from inexpensive materials such as soft copper tubes

and electrical PVC pipes, as shown in Fig. 1. The QFH consists of two loops, one smaller

than the other. The loops are constructed from soft copper tube, and joined at the corners

with 90 degree elbows. The helix is wound anticlockwise as seen from the top to provide

the proper polarization as used on the satellites. The connections at the top are made with

the braid of the RG-58 coax, connected to one side of the long loop, and bridged across to

the one side of the short loop. The center conductor of the RG-58 coax is connected to the

other side of the long loop. The mast is made from PVC tubing, and a 4-turn balun is

required and made from the coaxial cable [2].


Figure 1: Quadrifilar Helix (QFH) Antenna and Four-turn Balun

Designing the antenna prototype took several tedious steps. In order to be sure

that the antenna will be capable of capturing frequencies in the 137 MHz range, we

followed a guide that presented steps on how to construct the QFH antenna.

The first step of the design was to calculate the dimensions for every element. In

particular, the helix should be the same diameter throughout its length, and therefore the

length of the arms forming the helix is important. Eq. 1 shows the formula for this length,

l, where r is the radius and h is the height of the helix. The antenna guide instructed to

make the long loop’s height 560 mm and the shorter loop 512 mm. In addition, both

loops had a diameter of 355.6 mm. By using this formula, we calculated the lengths of

each loops and made adjustments to allow the use of 90° elbows instead of bending one

long piece of copper tubing to make each loop.

ℓ =√(πr )2+ h2(1)


The final design using 8 mm copper tube with the dimensions shown as cut

lengths for 137.55 MHz, shown in Fig. 2. Construction began by drilling four 8 mm holes

at the top of the mast at right angles. Four 8 mm holes were also drilled below but the

holes for the small loop were above the bigger loop holes by 24 mm. In addition, two

parallel 7 mm holes were also drilled slightly below the top holes for the cable entry and

exit, as shown in Fig. 1. The copper tubing was then straightened and cut into lengths to

the dimensions shown in Fig. 2.

Figure 2: Quadrifilar Helix Antenna with Dimensions

Next, the appropriate holes for the self tapping screws in the ends of the top

horizontal sections were drilled. The coaxial cable was fed through the hole into the mast


and then out of the top threading it through the hole in the center of the perforated circuit

board we cut to fit inside the PVC pipe, shown in Fig. 3.

Figure 3: Coaxial Connections on top of Mast

The top four horizontal tubes were then positioned inside the mast. In the original

design, the connections at the top of the helix were almost impossible to do inside the

mast, as the connection had to be made to the ends of the four tubes, two of which were

24 mm below the top two. Instead, we decided to bend the tops of the small loop by 24

mm so that all four tube ends were in a common plane at the top of the mast where they

can be reached, as seen in Fig. 4. Four turns of the feeder cable were wound around the

support mast to form the balun and taped into position.


Figure 4: Bending the Small Loop

The lower two horizontal sections were mounted in the mast and centrally

positioned. The four longest cuts of copper tube were carefully bent anticlockwise, and

copper elbows were placed on the top and bottom horizontal tubes. The bent sections

were positioned on the elbows to form the helix. Final soldering into place was done

using a gas torch and an end cap was placed on top for weatherproofing [7].

After assembling the antenna and testing that it operates in the 137 MHz

frequency range, the team will assemble the FM receiver. There were many available

options to make the receiver. The team considered making it from scratch, however there

are old receivers that we can use to modify or salvage parts for making the receiver. On

the other hand, there are receiver kits that can be purchased with all the components we

need. The team chose to use and modify an old receiver. The receiver chosen was the

Icom IC-2100 because it was provided at no cost to them by the project advisor, Dr.

Montiel.


Most modern receivers contain filters and amplifiers to process the antenna’s

signal, shown in Fig. 5. The antenna’s signal is first processed through a radio frequency

(RF) filter. For our application we need it to allow frequencies in the 137 MHz range.

The filtered signal is then amplified and sent into a mixer (multiplier). Mixers are used to

shift signals from one frequency range to another by comparing the amplified RF signal

with the Local Oscillator (LO). The LO shifts incoming tuned frequencies to a specified

range above or below the incoming tuned frequency. In typical FM receivers, the LO has

an output of 10.7 MHz about or below the incoming tuned RF, depending on the

particular intermediate frequency desired, and the method in which the LO frequency is

created. The output frequency then feeds the Mixer, and plays a critical part in FM

Heterodyning. Heterodyning is the mixing of a modulated carrier signal, FM in our case,

with a sine wave of another frequency (from the LO) to transfer the signal to a carrier of

different frequency. The Mixer produces the original RF, the original LO frequency, the

sum of the original RF and the original LO frequency, and the difference between the

original RF and the original LO frequency. The difference is called the intermediate

frequency (IF). Therefore, the original RF signal is transferred to and is contained within

the newly formed IF signal. Mixing effectively takes a received RF frequency and moves

it to a different, intermediate frequency, while retaining the original intelligence. The IF

is sent through an amplifier, processed by the phased-locked loop (PLL) where the final

output signal is produced [3].


Figure 5: Basic FM Receiver Block Diagram

Our receiver must also have a phase-locked loop (PLL) to provide frequency

selective tuning and filtering without the need for coils or inductors, shown in Fig. 6. The

PLL works as a feedback system comprised of three basic function blocks: a phase

comparator, low-pass filter, and a voltage-controlled oscillator (VCO). The VCO

operates at a set frequency which is known as the free-running frequency. If an input

signal is applied to the system, the phase comparator compares the phase and the

frequency of the inputs signal with the VCO frequency and generates an error voltage

that is related to the phase and the frequency difference between the two signals [4]. This

error voltage is then filtered and applied to the control terminal of the VCO. If the input

frequency is sufficiently close to the free-running frequency, the feedback nature of the

PLL causes the VCO to synchronize with the incoming signal. Once it is synchronized,

the VCO frequency is identical to the input signal, except for a finite phase difference.

This continual closed-loop feedback keeps the VCO running at very near to an integer

multiple of the data frequency. Any variations of the basic frequency of the incoming


data are thus tracked by the VCO, and the output of the PLL is a clock which is

frequency-locked with the data, allowing accurate definition of the bit period of the data.

Figure 6: Phase-locked loop (PLL) block diagram

In order to control the receiver, an interface had to be built between the PC and

the receiver. The team decided control the receiver by emulating the hand microphone,

the Icomm HM-98, which connects to the receiver by using the MiniDragon+. In order to

emulate the hand microphone, we needed to find out how the data was sent to the

receiver. First, we reproduced the data sent to tune the CB radio. We then used the serial

communication interface (SCI) port of our microcontroller to receive bytes from the

computer to tune to a desired frequency. This was implemented with the idea that a user,

who has no knowledge of the project or the programming behind it, can open the GUI

(Graphical User Interface) implemented with Visual Basic in conjunction with

WXtoIMG and be able to tune the radio to the frequency of an upcoming satellite.

WXtoIMG provides pass predictions, automatic recording, and image decoding in the


visible light and infrared spectrums. The MiniDragon+ and Visual Basic together provide

a way to tune the radio with the push of a button.

The first thing that we needed was information of the pin functions for the HM-

98. Table 1 below shows the pin functions for the HM-98 hand microphone [8].

Table 1: Pin Functions of HM-98

Through research, we discovered that the HM-98 sends data to control the

receiver through bit streams. When a key is pressed on the HM-98, a bit stream is sent to

the receiver and repeated until the key is released. The function key and secondary key

modify the actions of each key press. For our application, we will only use normal key

presses with no modifier. A table of this data can be found in Table 2.


Table 2: Waveforms Sent by HM-98 Hand Microphone

The first program was written to reproduce the bit streams sent to the receiver by

the handheld microphone. To verify the waveforms in Table 2, we studied individual bits

streams for each button press by connecting the HM-98 hand microphone to an

oscilloscope. Fig. 7 shows the bit stream for a ‘2’ being pressed. When the ‘2’ button is

pressed, the receiver goes into scan mode. To input an actual frequency the ‘C’ button

must first be pressed followed by the frequency you want to tune to. For example, if you

want to tune to 137.5 MHz you must follow this sequence of button presses: ‘C’, ‘1’,

‘3’,’7’,’5’,’0’,’0’.


Fig. 7: First Press bit stream (top) and Subsequent Press bit stream (bottom)

We found out that each button is encoded by sending a preamble consisting of

seven ‘0’ bits followed by a marker and two 20-bit streams indicating the first press of

the button. Another preamble and two more 20-bit steams are sent within a 43 ms period

indicating the subsequent press of the button, as seen in Fig. 7. The preamble is assumed

to gain the attention of the radio while the 20-bit stream contains several flag fields that

determine the function of the key press. A ‘0’ bit is encoded by going low for 190 us and

then bringing the signal high for 230 us. A ‘1’ bit is encoded by going low for 190 us and

going high for 415 us. The marker goes low for 190 us and high for 795 us. The term

‘low’ or ‘logic zero’ is interpreted by the receiver at 1.95 V. The term ‘high’ or ‘logic


one’ is interpreted at 2.45 V. To get these voltages we implemented a voltage divider, as

seen in Fig. 8.

Figure 8: Circuit for Voltage Divider

We used pins 0 and 1 of the microcontroller’s Port A to provide 5 V. Each pin

acted as a source. To acquire the voltage levels needed, we had to synchronize their “on”

and “off” stages. When a pin is “off” it provides 0 V and also grounds the resistor

connected to it. We chose to get our output from the node connecting the resistors.

Initially, we chose the center resistor to be 1 KΩ. From there it was a matter of solving

two equations simultaneously. Let’s say we choose V1 our source for “high” voltage and

V2 for the “low” voltage. When V1 = 5 V and V2 = 0 V we should get 2.45 V at the center

node. By using node current analysis, the current coming from the source should equal

the current that splits into the grounded resistors. The sum of the currents should equal

zero, as seen in Eq. 2:

5V −2. 45VR1

=2 .45V1 KΩ

+ 2. 45 VR2 (2)


Now let’s say we choose V1 = 0 V and V2 = 5 V to get our “low” voltage. The

result is similar, as seen in Eq. 3:

5V −1.95 VR2

=1.95 V1 K Ω

+ 1 .95VR1 ( 3)

Solving two equations with two unknowns yielded R1 = 180 Ω and R2 = 235 Ω.

To be able to tune the receiver with the MiniDragon+, we used three pins: the data

pin, ground, and the microphone ground pin (to make the receiver think the mic was

connected). The output from the middle node was fed to the data pin of the receiver.

The receiver “idles” at 2.45 V. Our program starts off by configuring pins 0 and 1

of Port A for output by moving the byte $03 to register $0002 (DDRA). Then we move

$02 to $0000 (Port A) to activate pin 1 and start the idling process. What follows is a

delay of 43 ms to allow some time for all internal components to be ready to receive data

inside the radio. There are four delays used throughout our program: 190 µs, 415 µs, 230

µs, and 795 µs delays. These are subroutines that are jumped to in order to encode our

zeros and ones properly. For example, to send a ‘1’ the high pin (PA1) is first cleared to

take care of any initial condition that might be encountered. The low pin (PA0) is set high

for 190 µs, then it is deactivated and PA1 is set high for 415 µs, and finally deactivated.

To send a ‘0’ is the same thing. PA1 is cleared before bringing PA0 high for 190 µs. PA0

is then cleared and PA1 is activated for 230 µs before being it is brought low again. The

marker follows the same pattern but PA1 is activated for 795 µs. These procedures to

send the ‘0’, ‘1’, and marker are used as subroutines in the main program. They are

simply called upon when it comes time to send the bit stream.

There is a pattern to every button press. Let us examine the “first press” sequence

for a ‘2’. A ‘2’ is entered with the following bit stream: ‘0100-0-1000-0-0111-0-0100-0’.


The dashes separate “columns” in the bit stream. The second, fourth, sixth, and eight

columns are always ‘0’. In addition, column 1 and 3 of every digit’s “first press” is the

same. In our program it is referred to as the universal byte for the “first press” because

every button uses it.

Now, let us examine the “subsequent press” sequence for a ‘2’ button press:

‘0000-0-1000-0-0111-0-0100-0’. It is similar to the first press sequence but the first

second bit changes. This is due to the fact that bits in the first column are flags. The first

1 in the sequence is the “first press” flag. In our program, column 1 and 3 for every

digit’s “subsequent press” is the same and referred to as the universal subsequent byte in

our program.

The first and third column bits of the first press and subsequent are joined as a

byte and saved in a memory. The universal first press and universal subsequent bytes are

$48 and $08, respectively. Columns 4 and 6 are also joined as a byte, $74, and stored in a

memory. Note that this byte is the same for both first and subsequent press.

After the main program runs the preamble it loads #2 into a counter which is also

a reserved byte. Then it moves the universal first press byte into a memory that we will

call the “decoder.” The job of the decoder is to be used as a catalyst for the sorting

process. A byte is loaded into the decoder and the program jumps to a subroutine that

logically shifts the memory left. The most significant bit (MSB) is sent to the carry flag

and it is checked. A branch-if-carry-set command is used to jump to the ‘1’ subroutine,

otherwise it jumps to the ‘0’ subroutine and looped back. This process checks the first

four bits before returning, jumping to a ‘0’ subroutine, and jumping back to shift the next

four digits of the decoder out. This way, the decoder is reset to $00 and the program


jumps to another ‘0’ subroutine before $74 is loaded into the decoder byte and the

process to shift the contents of the decoder restarts. This 20-bit stream is looped again

and the program enters a 43 ms delay. After that program jumps to the preamble

subroutine and the universal subsequent byte is loaded into the decoder and the process is

repeated to send the subsequent press 20-bit stream twice.

This process is just for one byte; in order to tune the radio to the desired

frequency, we loaded the second byte for reach digit into succeeding memory bits. The X

register is used as a pointer. Meaning that the address of the ‘C’ is stored in X and after it

goes through the process of sending the required bit streams, X points to the byte

representing a ‘1’, and so on, until the last ‘0’ digit is sent. The final code is located in the

Appendix.

After having a functioning code to tune the receiver, the SCI (serial

communication interface) code was written. The 9S12 chip has two SCI ports: SCI0 and

SCI1. These pins are shared with Port S when not in use. However, by enabling the

receiver or transmitter pin we turn off the pin connection to Port S and turn on the pin

connection to the TX and RX registers. The SCI0 port is hooked up to the RS-232

interface via the SP232AEN chip. When you talk to DBug-12 with your PC, all the data

are coming in/out of the SCI0 port via the SP232AEN. The chip alters the levels of the

9S12 SCI voltage levels to be compatible with the RS-232 standard. The SCI input/output

voltages are TTL type where 0 V is logic low and +5 V is a logic high. RS-232 on the

other hand uses negative logic where logic high is typically around -12 V and a logic low

is typically around +12 V. The SP232AEN does all these voltage conversions

automatically. For instance, a +5 V high output from the SCI to a -12 V output on the


RS-232, or a +12 V RS-232 input to a 0 V SCI input. [9] For our program, SCI1 was

used instead of SCI0 because we didn’t want to mess with DBug-12. The SCI

configuration allows for a number of options for data transmission and reception. In the

simplest configuration, ten bits are involved: a start bit (logical 0), the 8 data bits, and a

stop bit (logical 1). Fig. 9 shows an example transmission waveform, such as what you

might see if you hooked up a logic analyzer to the TX pin. Note that the data bits are sent

least significant bit (LSB) first, and MSB last. The middle 8 bits in the pulse train in Fig.

9 are sent in the order ‘10110100’ in a time domain signal, corresponding to an actual

data byte for $2D (00101101).

Fig. 9: Transmitting an ASCII minus “-“sign

The data rate out of/into the SCI is determined by the baud rate, and is an

essential value to consider in any SCI setup. For the NRZ (non-return to zero) encoded

waveforms of the SCI, the baud rate is the same as the bit rate, so a baud rate of 9600

corresponds to a bit rate of 9600 bits/sec. The baud rate is determined by Eq. 4:

SCI BAUD rate=24 MHz16×BR ( 4)


BR refers to the content of the SCI1BDH/L Baud Rate Registers at addresses

$00D0 and $00D1. For example, for a baud rate of 9600 (baud period ~ 100 us), we want

a BR of about 156 = $9C, so we write $00 to SCI1BDH and $9C to SCI1BDL. Note that

the baud rate is the same for transmission and reception for a given SCI port; we can't set

one baud rate for transmission and another for reception on a given port. Also note that

we must always closely match the baud rates between a transmission/reception pair of

devices. If one device is transmitting at 9600 baud, the receiving device it is connected to

must be configured to receive at 9600 baud.

Since we only need to receive data from the RS-232 controlled by the PC, we

only need to activate the receiver pin. We enable the receiver by setting the RE (receiver

enable) bit of SCI1CR2 Control Register at address $00D3. Once enabled the receiver is

optional, and waiting for data. We then wait for the shift register connected to the RX to

fill with serial data. The RX register waits until it sees a 1 to 0 transition signifying a start

bit. Then read data into the shift register (LSB first) in a serial fashion at the selected

baud rate. Think of the received data coming in on the left side of the receive register and

shifting to the right, so that the LSB then corresponds to bit 0. Thus, the bits that we read

will be aligned correctly in the receiver data register, with the LSB at bit 0 and the MSB

and bit 7.

Once the shift register is full, the data is then transferred to the data register

SCI1DRL at address $00D7. This will set the Register Data Register Full (RDRF) flag,

indicating that we can now read the received data in register SCI1DRL.

Basically our program waits for the RDRF flag to go off, and then the contents of

SCI1DRL are moved to accumulator A. From there a byte is transferred to accumulator


B. Their contents are compared and if equal, the program branches to a program that

tunes to the desired frequency. If not equal, then it runs on an infinite loop until another

bytes is sent. There are three bytes of interest. Since we want to tune to 137.50, 137.10,

and 136.62 MHz, the numbers after decimal were selected as the bytes we look for in our

program. For example, byte $50 tunes the CB radio to 137.5 MHz. By pressing the button

on the user interface, a byte is sent and picked up by the MiniDragon+. From there it

branches to a tuning subroutine, and it waits for the next byte.

Once the signal is processed, it will be fed into the computer where the receiver

frequency adjustments, image decoding, and satellite tracking will take place.

Initially, we will need to know the positions of the satellites. Satscape is a free

tracking program that can be used to find the position of 8000+ satellites. Pass

predictions can be calculated and displayed. Speech announcements are made to alert the

user when a satellite is about to pass over. In addition, it provides us with the satellite’s

longitude, latitude, speed, and elevation information [5].

The receiver will be interfaced with the computer through its serial port using

Visual Basic and SCI. The receiver will connect to the PC’s microphone jack in order to

input the signal to the soundcard.

Finally, the image processing will be done with a program called WXtoImg [6].

This program is free and is said to be the world’s best weather satellite signal-to-image

decoder. The software makes use of the 16-bit sampling capabilities of soundcards to

provided better decoding. The proposed system as a whole is presented in Fig. 10.


Figure 10: Home Weather Satellite Receiver Station

2.2 Statement of Work

The project will be divided into different task; each individual task is described

below:

Task 1: Build the antenna prototype.

Task 2: Modify the FM receiver.

Task 3: Test the antenna and receiver.

Task 4: Acquire necessary data.


III. RESOURCES

3.1 Personnel

The project workload will be split between the three teammates. The

responsibility of constructing the quadrifilar helix antenna belongs to Mr. Dulavitz. Mr.

Perez and Mr. Reyes are responsible for the FM receiver used to receive the radio

frequencies transmitted from the weather satellites. Mr. Perez will be focused on the

hardware aspect of the FM receiver while Mr. Reyes will be focused on the software

aspect and interfacing the receiver with the PC. In addition, all three teammates will work

together to overcome any obstacles that may occur when working on each individual part

of the project.

3.2 Facilities and Equipment

Most of the work will be done in the Senior Project Lab located in room 130 of

the Engineering Complex. This includes the use of any soldering irons and the use of any

computers provided in the Senior Lab. Any welding required for the antenna will be done

at the Machine Shop located in the McNeil Engineering building. Additional equipment

may be necessary to complete the project.


IV. COSTS

4.1 Budget

The project will require the acquisition of components that will make the system

fully functional. Many of the elements needed to construct the prototype antenna can be

found in a regular hardware. Excluding the PC, the receiver will be the most expensive

piece of equipment that would have to be acquired. The FM receiver we used was one

that we already had on hand and did not have to purchase. It is also an older model that is

no longer in stock, so the quoted price is an MSRP.

Table 3 shows a list of the components that will be employed in the development

of the system. It is important to note that this budget was compiled with the assumption

that the project is started with no readily available equipment. For example, the

computers and soldering irons are provided in the senior design lab but are still included

for cost analysis of the project as a whole.

Table 3: Components List and Cost


4.2 Timeline

We will start working on this project at the beginning of the Spring 2011

semester. The dates shown in the timeline in Fig. 11 represent the approximate time that

we expect to have completed the described task. The markers indicate major goals that

will be achieved with according dates.

Figure 11: Project Timeline


VI. Data Analysis

5.1 Procedure

We set our initial test run up in the EC 130 Senior Lab on February 28, 2011 at 5

P.M. We used a power supply and set it to 13.8V to power the IC-2100 receiver. We

plugged the antenna into the rear of the receiver and took the antenna outside. An audio

cable was then plugged into the audio out of the receiver and connected to the

microphone in of the PC used. WXtoImg was then run on the PC. When the NOAA 15

satellite was in range, we then ran the recording software. The image processing was

done by the software.

5.2 Data

Fig. 12 shows the first satellite image obtained from the antenna and receiver

system. The satellite was in range for about 10 minutes. The image on the left is Channel

A of the satellite. Channel A is the normal satellite view of the Earth. Channel B of the

satellite is on the right side. Channel B is the thermal view and was not as clear in the

image that we received compared to Channel A.

To verify the effectiveness of our antenna, we connected our quadrifilar helix

antenna to a vector analyzer. The vector analyzer would measure the s-parameters of the

antenna to determine reflection and transmission of the load. We will use this information

to determine the resonance frequency of our antenna to see if it is a good match. We

designed our antenna to work at 137 MHz. Fig. 13 shows the results of the vector

analyzer and that our resonance frequency is at 133 MHz. This means that there is little


power reflected and that the antenna is a very close match to the 137 MHz that we

designed our antenna for.

Figure 12: NOAA 15 Satellite Image on 2-28-11


Figure 13: Resonance Frequency of Antenna

5.3 Interpretation

We were able to obtain a somewhat clear image of the NOAA 15 satellite. The

first couple of minutes contained noise that could be attributed to the antenna being next

to the building when the satellite first appeared in range. As the satellite moved closer

overhead, we were able to receive a much clearer picture. As the satellite moved out of

range, we received more noise until we received no signal at all. The overlay of the states

and provinces on the map was added automatically by WXtoImg. Also note that this test

was done manually as the program for automating the receiver was not complete at the

time of the test.


V. Conclusion

The project was studied and was done. The team’s proposed plan contained in this

report was followed as closely as possible. The proposed timeline and budget were

followed to the best of the team’s ability in completing the project, even with changes in

design. Each team member had his assigned task to finish, but the team worked on the

entire project as a whole. The project began at the start of the Spring 2011 semester and

was completed on April 20, 2011.


REFERENCES

[1] http://www.hobbyspace.com/Radio/WeatherSatStation/intro.html#NOAAsats

[2] http://va6bc.no-ip.com/jerry_pix/Quadrifilar-helix/quadrifilar_helix_antenna.htm

[3] http://www.drhull.com/awh_files/FM%20report.pdf

[4] http://en.wikipedia.org/wiki/Phase-locked_loop

[5] http://www.satscape.info/modx/index.php

[6] http://www.wxtoimg.com/

[7] http://www.rocob.plus.com/

[8] http://tinymicros.com/wiki/Icom_HM-98/HM-133_Internals

[9] http://wwwold.ece.utep.edu/courses/web3376/SCI%20Overview.html


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