SDR: Software defined radio


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    Download file "SDR radio notes.pdf"
    Why SDR?
    • Most radios you use everyday are SDR, including your iPhone or android
    • Software defined radios rely on computing power instead of hardware, so the are more flexible, cheaper, and in some cases can handle complex encoded communications like cellular or digital communications
    What is SDR?
    • First generation hardware defined radio is a method of transmitting information using electromagnetic radiation (EMR waves) through an antenna to space, then picked up by a receiving antenna as electrical and magnetic fields. The antenna is wired to a series of resistor/capacitor/inductor circuits to discern the information from the electrical pulses, then amplified for the listener. Your car radio or portable radio still use this technology.
    • SDR or software defined radio connects to the receiving antenna as above, but converts the electrical signals into digital ones and zeroes (1, 0), which can then be processed by a computer. Since the processing happens on a digital level, the power of the computer is the only limiting factor to the complexity of the signal processing.
    Here's a comparison:
    Top is a normal radio, note the parts:
    The lower image is an SDR. Note that both have an antenna and some sort of basic amplifier to make the signals easy to process, but the SDR converts the analog signal to digital, using an A/D converter (analog to digital).
    Why should I care?
    If you learn about SDR, you can understand digital music production, wireless networks, space communications, telecommunications and much more...

    How we will use it:
    We have several very sensitive antennas each connected to an SDR converter on our IP computer network.
    By using any of a number of SDR programs on your computer, you can connect to these SDR radios, and use them to receive programs from around the world, depending on which direction the sensitive directional antennas are pointing.
    (You could also transmit using these antennas with an SDR transceiver, which is a receiver and transmitter in one)
    Programs we will use: SDRdx, SDR#, Airspy
    Mac version:
    Download file "SdrDx-AA7AS-Light.zip"
    PC version:
    Download file "SdrDxDist.zip"

    How to use this:
    First, the IP addresses, which often change:
    Second, download the proper version (mac or pc) to your computer
    On the mac, you might want to put this in your applications folder
    To open, you may have to hold control while opening the SDRdx app in the folder

    Here is a screenshot of what you will see when you open the app:
    Lots here, don't be intimidated...
    Look at the lower left for net:

    Insert the IP address of one of the radios. Note: only one person can access each radio at the same time.
    Look lower left for "SDR"
    Make sure the GSP is either 200 or 190 kHz for our radios
    Look upper left for "RUN"
    You might want to click on "PAL" to make it color, but you should see something like this:

    The sensitivity is done on the upper left, where it says: MAX dB
    If it is all orange, adjust until you can see blue.
    The frequency is selected by using either BC (broadcast) or AR (amateur) bands.
    Try clicking through them, then clicking on the waterfall to hear the stations.

    A guide:
    Download file "SDRdx screens.png"