1. Introduction


Electromagnetic waves are waves which can travel through the vacuum of outer space. They are created by the vibration of an electric charge. This vibration creates a wave which has both an electric and a magnetic component. An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c). The propagation of an electromagnetic wave through a material medium occurs at a net speed which is less than 3.00 x 108 m/s. (Physics classroom, n.d.)

Amplitude Modulation has been in use since the very earliest days of radio technology. The first recorded instance of its use was in 1901 (Poole, n.d.) To achieve this, he (Reginald Fessenden,1901) used a continuous spark transmission and placed a carbon microphone in the antenna lead. The sound waves impacting on the microphone varied its resistance and in turn this varied the intensity of the transmission. Although very crude, signals were audible over a distance of a few hundred metres. The quality of the audio was not good particularly as a result of the continuous rasping sound caused by the spark used for the transmission.
Later, continuous sine wave signals could be generated and the audio quality was greatly improved. As a result, amplitude modulation, AM became the standard for voice transmissions.
Radios have been a very important form of telecommunication in our daily lives. Despite the fact that telecommunication has always been constantly improving eg. smartphones from brands such as Apple & Samsung, radio still remains as a very important form of communication. Their importance is especially so when there is an urgency to give out important announcements as soon  as possible.

1.1 Problem being addressed


Communication in SST can be further improved and enhanced to be more effective and quicker in passing informations/announcement. We feel that, despite having apps such as SST Announcer to pass information, this can be used as to pass information/signals between two parties.

     1.2 Engineering Goals

We want to find out how to make an AM Transceiver Radio and to find out how it works. If we managed to make our AM Transceiver Radio work, this will improve and enhance communication within selected parties of the school (eg Student Councillors communication with Teachers) or as a whole student body.


1.3 Specific Requirements
In particular, we wanted to  
  1. Test if it can transmit across 100m
  2. Test if it can transmit on rainy/sunny days
  3. Test if it can be transmitted even when at different levels of altitude eg. 1 at Level 1, another walky talky at level 2


1.4 Alternative Solutions
1.4.1 Design 1
Method 1 Diagram .jpg
FIGURE 1
FIGURE 1: The above shows a completed diagram taken from Science Buddies (2016) as a completed product. It shows a phone (as the audio playing device), the breadboard (as the transceiver device), and batteries that supply the energy.

Equipment needed for solution 1


No.
Equipment
Quantity
1
AA Battery Holder
1
2
Music Playing Device with 3.5mm audio output jack
1
3
AM Radio
1
4
Solderless Breadboard
1
5
AA Batteries
4
6
1 MHz “full can” crystal oscillator
1
7
1000 Ω to 8 Ω audio transformer
1
8
Jumper wire kit
1
9
3.5mm stereo cable
1
10
Wire stripper(s)
1

1.4.2 Design 2
FIGURE 2

      FIGURE 2: The above shows the completed circuit of the project that we would be doing from Instructables (2016). It has been personally labelled by us to ensure convenience of understanding the diagram. This will eventually be our prototype if the method is used.

Equipment List:

Item no.
Item
Quantity
No. 1
Some wire
About less than 20
No. 2
1 crystal with a frequency that is between 0.9 and 1.2 MHz
1
No. 3
1 male headphone jack

1
No. 4
Breadboard or experimental circuit board.
1

1.4.3 Design 3

Figure 3: The figure above shows a completed version of the Li’l 7. The parts labelled are confirmed. Parts that are unnamed are not stated

Figure 3.1: The figure above shows a the circuit diagram of the Li’l 7


Solution 3 (Antique Radio, 2016)  is a more complicated solution compared to other solutions. This also is the biggest in size, and most complicated to operate.

Equipment List:


Part
Description
Part No.
Quantity
Price (ea.)
C1
220pf ceramic capacitor
AES C-D220-6000
1
0.44
C2
.01mf 600v capacitor
AES C-RD01-600
1
0.59
C3, C4
22mf 160v electrolytic capacitor
AES C-ET22-160
2
0.98
C5
68pf mica capacitor
AES C-SM68
1
0.45
C6
150pf mica capacitor
AES C-SM150
1
0.51
J1
RCA quad phono jack
Radio Shack 274-322
1
1.69
J2
8-pin tube socket
AES P-ST8-209M
1
2.70
L1
RF coil
AES P-C70-RF
1
7.95
P1
12v lamp assembly
Radio Shack 272-336
1
2.59
R1
47K ohm 1/2-watt resistor
AES R-A47K
1
0.08
R2, S1
100K potentiometer & switch
Mouser 31VM501-F
1
1.72
R3
10K ohm 1/2-watt resistor
AES R-A10K
1
0.08
T1
120v/12v Power transformer
AES P-T442
1
16.95
V1
117L7 or 117M7 tube
AES 117L7
1
6.60
Misc.
120v power cord
AES S-W104
1
1.50
Misc.
Antenna wire (24 ga. enamel)
AES S-WL3-612
1
3.00
Misc.
Alignment tool kit
AES S-T9304
1
1.25
Misc.
Perforated project board
1

Solution 4


Figure 2: Image of a completed circuit that shows the powers of the resistors, transistors and capacitors



Screenshot 2016-02-01 10.16.06.png
Figure 3: Image of completed connection with battery (power source), speaker (audio), antenna with circuit board.

Equipment List :

Item no.
Item
Quantity
No. 1
Future Kit WALKY TALKY 27 MHz CODE 711
1
No. 2
Battery Holders

2
No. 3
AA Batteries

12

1.4.4 Decision making matrix

Table 1: Decision and Ranking Matrix

Criteria
Safety
Robustness
Size
Skill Required
Row Total
Normalised Value
Safety

3
3
3
9
0.3
Robustness
4

4
4
12
0.4
Size
1
1

1
3
0.1
Skill Required
2
2
2

6
0.2




Column Total
30


Criteria
Normalised Value

Design/ Solution Alternative 1 (AM Transmitter from Science Buddies)

Solution Alternative 2(from Instructables.com

Design/ Solution Alternative 3 (from antiqueradio.com)

Design/ Solution Alternative 4 (from FutureKit F711 Walky Talky)

Safety
0.3

2
0.6
3
0.9
1
0.3
3
0.9
Robustness
0.4

4
1.6
3
1.2
1
0.4
4
1.6
Size
0.1

3
0.3
2
0.2
1
0.1
4
0.4
Skill Required
0.2

4
0.8
3
0.6
2
0.4
3
0.6



Total
3.3
Total
2.9
Total
1.2
Total
3.5

Table 2 : Solution Matrix

1.4.5 Best solution and rationale

Thus, from the table, we deduce that Solution no.4 is the best. From the tables above, we are able to tell that Solution no.4 is safe, robust, has a reasonable size and is relatively easy to use.

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