1. presented by the USA School of Computing
Radio Free USA Building a low-power RM transmitter using a Raspberry Pi
presented by the USA School of Computing

2. The Electromagnetic Spectrum
Band name
Abbreviation
ITU band
Frequency and wavelength
Example uses
Tremendously low frequency
TLF
< 3 Hz > 100,000 km
Natural and artificial electromagnetic noise
Extremely low frequency
ELF
3–30 Hz 100,000 km – 10,000 km
Communication with submarines
Super low frequency
SLF
30–300 Hz 10,000 km – 1000 km
Ultra low frequency
ULF
300–3000 Hz 1000 km – 100 km
Submarine communication, communication within mines
Very low frequency
VLF 4
3–30 kHz 100 km – 10 km
Navigation, time signals, submarine communication, wireless heart rate monitors, geophysics
Low frequency LF 5
30–300 kHz 10 km – 1 km
Navigation, clock time signals, AM longwave broadcasting (Europe and parts of Asia), RFID, amateur radio
Medium frequency MF 6
300–3000 kHz 1 km – 100 m
AM (medium-wave) broadcasts, amateur radio, avalanche beacons
High frequency HF 7
3–30 MHz 100 m – 10 m
Shortwave broadcasts, citizens' band radio, amateur radio and over-the-horizon aviation communications, RFID, over-the-horizon radar, automatic link establishment (ALE) / near-vertical incidence skywave (NVIS) radio communications, marine and mobile radio telephony
Very high frequency
VHF 8
30–300 MHz 10 m – 1 m
FM, television broadcasts and line-of-sight ground-to-aircraft and aircraft-to-aircraft communications, land mobile and maritime mobile communications, amateur radio, weather radio
Ultra high frequency
UHF 9
300–3000 MHz 1 m – 100 mm
Television broadcasts, microwave oven, microwave devices/communications, radio astronomy, mobile phones, wireless LAN, Bluetooth, ZigBee, GPS and two-way radios such as land mobile, FRS and GMRS radios, amateur radio
Super high frequency
SHF 10
3–30 GHz 100 mm – 10 mm
Radio astronomy, microwave devices/communications, wireless LAN, most modern radars, communications satellites, satellite television broadcasting, DBS, amateur radio
Extremely high frequency
EHF 11
30–300 GHz 10 mm – 1 mm
Radio astronomy, high-frequency microwave radio relay, microwave remote sensing, amateur radio, directed-energy weapon, millimeter wave scanner
Terahertz or Tremendously high frequency
THz or THF 12
300–3,000 GHz 1 mm – 100 μm
Terahertz imaging – a potential replacement for X-rays in some medical applications, ultrafast molecular dynamics, condensed-matter physics, terahertz time-domain spectroscopy, terahertz computing/communications, sub-mm remote sensing, amateur radio
Source: wikipedia.com

3. The Electromagnetic Spectrum
Source: wikipedia.com

4. The FCC and Licensing
Over 30,000 requests for licenses are received each year. Most are denied.
In many areas of the country, no frequencies may be available on which a new station could begin operating without causing interference to existing stations, a violation of FCC rules.
The only unlicensed operation that is permitted on the AM and FM broadcast bands is covered under Part 15 of the FCC's rules, and is limited to a coverage radius of approximately 200 feet.
FM noncommercial commercial (NCE) stations may be authorized on 88.1 MHz to 91.9 MHz.  No commercial operation is permitted on these frequencies. Both noncommercial and commercial stations may be authorized on 92.1 MHz to MHz
Source:

5. What is a Raspberry Pi A raspberry pi is a small computer
It has HDMI out, video out, USB
ports, and an Ethernet connection
It uses a SD card as its hard drive
You can download prebuilt images
for different operating systems from

6. Getting Started From the adapter, remove the SD card
Insert into the Pi
The SD card is spring loaded
Connect the Ethernet cable to the Pi
Connect the other end of the Ethernet cable to the PC
Connect the power supply to the Pi and plug it in to a USB port on the laptop

7. Using the Pi with no monitor?
If you don't have an HDMI monitor available, then you use a program called VNC to use your laptop or desktop to view the Raspberry Pi desktop
VNC stands for Virtual Network Computing
When you connect with VNC, you will see the desktop of the Pi on your PC, and you will be able to use your keyboard and mouse

8. How to connect to the Pi
At your desks, you will find an SD card that has an image already installed on it
This image presets the IP address of the Raspberry Pi to
An IP address is a unique number assigned to a machine
It is how machines communicate with each other
In order for your PC to talk to the Pi, we must change its IP address

9. VNC Setup Instructions
Go to Start -> Control Panel and choose Network and Sharing Center

10. VNC Setup Instructions
Click on Change Adapter Settings
Right Click on Local Area Connection
Then select Properties

11. VNC Setup Instructions
Choose Internet Protocol Version 4
Then select Properties

12. VNC Setup Instructions
Enter for the address and for the Subnet mask

13. How do we access the Internet ?
One solution to this problem is to purchase a wireless dongle for the Pi
If you don't want to purchase this, you can use your laptop as a proxy
In order to set up your laptop as a proxy, you will need to install a proxy server
The URL has instructions about how to download a program called Squid

14. What is Squid? Squid is a well known proxy server
What you will find at the URL are instructions about how to download a windows port of Squid and set it up
On the PCs, we already have Squid on it
Squid listens at port 3128 by default
We must configure the PC to allow the Pi to connect to port 3128

15. Squid Setup Instructions
Go to the Control Panel and choose Windows Firewall
Click Advanced Settings

16. Squid Setup Instructions
Choose Inbound Rules
Click New Rule

17. Squid Setup Instructions
Click Port

18. Squid Setup Instructions
Type in 3128 for the port number
Click next

19. Squid Setup Instructions
Choose Allow this connection

20. Squid Setup Instructions
Choose public and private

21. Squid Setup Instructions
Enter the name Squid for the service

22. Squid Setup Instructions
Go to the Control Panel and open Administrative Tools

23. Squid Setup Instructions
Double-click on Services

24. Squid Setup Instructions
We see the Squid service
Click on Start the service

25. Squid Setup Instructions
After you click Start, you see the Squid service has started

26. SSH and VNC What we will use to connect to the Pi from the PC is SSH
SSH stands for Secure Shell
It is a standard program for connecting to servers
It provides an encrypted connection
We can also tunnel ports through the connection
Tunneling means instead of connecting as your normally would where traffic is exposed, the connection to the distant server goes through the encrypted connection

27. How do you use SSH? A popular tool to use SSH is putty
On your laptops is a Java program that uses SSH to tunnel a connection to the Pi
It carries the VNC connection
On your local machine port will be translated to port 5901 on the Pi
Turn on the Pi if you haven’t already
Double-click ConnectToPi.jar and click Connect to Pi. You should then see the Pi desktop.

28. ConnectToPi.jar Step 1: Click the button that says Connect to Pi
Step 2: Click the box that says you have read the agreement and click OK
Step 3: Click the box for Don't warn me about this again
Step 4: Success!

29. What is available on the Pi?
This version of the operating system contains
Python 2 and Python 3
Mathematica
Web browser
Games
Scratch

30. The terminal We can open a terminal so we can type commands
At the top, you will see an icon for the LX Terminal
This is the equivalent of the command prompt in Windows

31. Some simple commands
In order to view the files in a directory, we use the command ls
To see a detailed list, we use the command ls -l
The change to a different directory, we use the command cd
One thing that is important to know is that, as the user pi, we do not have access to files in all directories
We also don't have the ability to run all programs

32. sudo
In order to access these files, we must elevate the privileges of the pi user
In order to do this, we must precede a command with the word sudo
This elevates the pi to the superuser
To see this in action, change to the directory /etc and type nano test
If you click CTRL and O to save the file, you will be told you don't have permission
Now change the command to sudo nano test and try to save the file

33. Wget Setup Wget allows us to download files via the command line
Edit the configuration file for wget

34. Wget Setup
Verify the http_proxy is set to our proxy

35. We now edit the configuration file for apt (Advanced Packing Tool)

36. Type in the following to use the proxy. Make sure you include the ;

37. Turning the Raspberry Pi into an FM Transmitter
Type the following commands at the command prompt
wget
gunzip Pifm.tar.gz
tar xfv Pifm.tar.gz
Attach a cable to pin 7
sudo ./pifm sound.wav 100.8
pifm will play only wav files
To convert mp3 files to wav files, type the following commands
apt-get install libav-tools
avconv -i mp3file -ac 1 -ar b 352k filename

38. How to transfer files to and from the Pi
We can transfer files to and from the pi using ssh
We can use the program pscp to download from the site where we downloaded putty
This program allows us to transfer files on the command line
If you want to use a graphical interface, you can use the program WinSCP

39. How to use pscp
Since your pi is connected to your PC, we will transfer files directly from the PC to the Pi
c:\tem\pscp file
This says to take the file and transfer it to the pi. In order to transfer using ssh, we must first login. The account is specified before After the IP address, we must have a colon followed by the location where we want the file to be placed on the pi
After we hit enter, we will be prompted for the password. It is pi123

40. Clean Up
After you are finished, reset the network settings to DHCP on the laptop