1. Final Lab – EGRE 307 Spring 2015
Building a Communication System
Jacob Ramey
Ryan Littleton
Wesley Houk
Ritvik Nag

2. Requirements
600kHz Carrier with 20Hz-20kHz message
THD of less than 15%
Transmit across 5m (~16 feet)

3. What we got
580kHz Transmission (3.4% difference)
THD of 3.4%
Transmits ~10 feet via handheld radio
Transmits ~2 feet via receiver

4. Transmission Side
Input
Input
Amplifier
ModulatorOscillator
Transmission
Amplifier

5. • Input from a
3.5mm jack
• Op-Amp
amplifier with
gain of 4.7 V/V
Input / Amplifier

6. • Colpitts
Oscillator
• 590kHz
• THD of 8.9%
Oscillator

7. Oscillator
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-6.00E-06 -4.00E-06 -2.00E-06 0.00E+00 2.00E-06 4.00E-06 6.00E-06
Voltage
Time

8. • Conventional
Amplitude
Modulation
(Non-
Suppressed
Carrier)
Modulator

9. Modulator
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
-0.001 -0.0005 0 0.0005 0.001
Voltage
Time

10. • Common
Emitter
Amplifier
• Gain of 7 V/V
Transmission Amplifier

11. Transmission Amplifier

12. • Quarter wave
monopole
• 58 inch copper
tube
• 125 meter
loading coil
Antenna

13. Receiving Side
Receiver
Amplifier
Envelope
Detector
Output
Amplifier
Output

14. • Amplifies
signal received
from antenna
• Two cascaded
amplifiers for a
total 8 V/V gain
Receive Amplifier

15. Receive Amplifier

16. • Passive
Envelope
Detector
• DC biased
Envelope Detector

17. Envelope Detector

18. • Op-amp based
amplifier
• Gain of 4.5 V/V
Output / Amplifier

19. Video

20. Questions??
Acknowledgements
• Rameez for help with receiver
• Dr. Filippas for being awesome