Information in Radio Waves
Inquiry Project: Investigating Radio Signals with Software defined Radio (SDR)
Signal Defined Radio (SDR) is a technology that enables users to capture radio transmissions
and decode them using only software instead of the physical components of a traditional radio
system. This is done by encoding the signal processing components as programs and
incorporating them onto a processor chip. The benefit for this technology is that it will enable
greater flexibility and adaptability for devices that use radio communication. Instead of having a
hardware system that conforms to a single set of standards and protocols for sending or
receiving signals, the software can be programed to use a multitude of standards and protocols.
As systems and technologies develop in the future, the software systems have only to be
updated or re-programed to accommodate the new developments. Applications include
machine to machine communications and robotics. In this activity you will use an SDR receiver
to investigate the radio transmissions around us.
Project Requirements
Part 1: Exploring local Radio (formative)


Explore the physics of radio through FM transmission
Product: Analysis questions
Part 2: Observation of basic signal properties (formative)


Observations of the characteristics of the signal as ‘observed’ at
the receiver.
Product: recordings
Part 3: Analysis of Signals (formative)

results are presented in graphical display
Part 4: Report on investigations with the FM transmitter


Final product can be a written report, a blog, a presentation, or
Scoring rubric (appendix c) linked to
NGSS Standards assessed:
HS-PS4-5
HS-PS3-3
RET 2013
Communicate technical information about how some technological devices use the
principles of wave behavior and wave interactions with matter to transmit and capture
information and energy.
Utilize a device that works within given constraints to convert one form of energy into
another form of energy.
1
Information in Radio Waves
SDR Project
Investigation 1: Tune in to a local FM station (Near Boston find 99.5 WCRB – Classical
New England)
When you are tuning your SDR to a frequency, you are simply adjusting the “window” within which the
software is processing and outputting data for audio (listening). The two visual displays will allow you to
visualize the signal that is being intercepted by the antenna.
Procedure:
 Follow the set up procedures for both the RTL receiver and the SDR# software in Appendix 1 and 2.
 Plug in the USB stick and attach the antenna
 Start SDR#
 Tune the radio to a frequency of 99.5 MHz
Introductory analysis and questions:
There are many features to this software interface
that are highly technical with respect to the signal
processing and analysis of radio signals. You will
only be using a few of them in this activity
In the top view you see an x-y line graph that is
continuously updated (hence the noisy look).
What are the units on the x-axis?
____________________________________
What are the units on the y-axis?
____________________________
In the FFT Display plugin, select the IF spectrum
and the audio spectrum.
What is the width of the IF spectrum band in frequencies?
Once you have the peak set up, take the db value of the baseline and the top of the
peak. Find the difference to get a pseudo-power estimate. This is how much power is
being collected by our antenna. Record your answer below.
RET 2013
2
Information in Radio Waves
Investigation 2: What are those crazy –db units?
In radio science we often are dealing with quantities that have very wide ranges such as factors of one
thousand to millions. Representing numbers that have such a high range can be difficult. The unit db is
used to show the power of 10 differences in quantities. 1 db is simple 101, 0.1 db = 10-1. On the
screenshot you will see a spectrum (with a lot of Radio frequency interference, RFI) of a local radio
station 99.5 WCRB near Boston MA. Notice the y-axis of the plot, it goes from 0 at the top to -40 or so
where it joins the x-axis. Which is a higher actual value -10 db or -40 db?
Now you will learn some factors in how the power output from the transmitter station is received and
why we are getting the numbers that we are getting.
Part 1: Where are we relative to the station?
You can find the distance between your location and the transmitting station by plugging in the latitude
and longitude for both into an online calculator. The calculator uses some interesting geometric
properties to find the distance from one point on a sphere to another, of course assuming the earth is a
sphere. I recommend this caluculator, http://www.fcc.gov/encyclopedia/distance-and-azimuths-
between-two-sets-coordinates
First, gather some information about your radio station:
Station carrier frequency MHz
Height above ground
ERP (Estimated Radiative Power)
Latitude
longitude
Transmitting station
Your location
Distance in meters
The key quantities from the data you have collected are the ERP, how much power is being emitted by
the transmitter, and the distance from the source, D.
RET 2013
3
Information in Radio Waves
Part 2: The inverse-square law for radiative power
Estimating the received power using the irradiance invariance law, the energy from the station must be
conserved, so as it extends in all directions it spreads out over a larger area and is decreased for that
reason.
The illustration to the left shows the inverse
square relationship between Intensity and
the radius of the imaginary sphere extending
out from the source.
In our case the ERP is the source strength
And the power density , p, is the source
strength where D is our distance between
our location and the transmitter.
𝑝=
𝐸𝑅𝑃
4𝜋𝑟𝐷 2
The power at the receiver is then:
𝑃𝑟 = 𝑝𝐴𝑟
Where pr is the power received by the receiver antenna, p is the power density from the transmitter,
and Ar is the surface area of the receiver antenna. Use the values that you found for the ERP and the
Distance, calculate the power density from the transmitter and the power at the receiver in the space
below. Rewrite the equations with our values substituted in and show your calculations with correct
units.
This is an increadibly idealized situation. Take a look at some of the assumptions that are made:



it assumes that the radiation is emitted equally in all directions, isotropically, which NEVER
happens with antennae.
It also assums that there is no interference with the ground, water dropplets, etc…
It also assumes that every surface of the antenna will collect radiation equally, which doesn’t
happen in reality.
Given all of those assumptions, explain how your theoretical db value compares with what is being
recorded and what you think is causing the difference if there is any?
______________________________________________________________________________
______________________________________________________________________________
RET 2013
4
Information in Radio Waves
SDR Project
Part 3: Basic signal observations.
Set up the receiver and SDR# software in the same configuration as for investigation 1 and tuned to 99.5
MHz WCRB.
1. Measure how wide the peak is by rolling the mouse over either edge of the peak
a. Left edge =______________________
b. Right edge=_____________________
c. Difference=_____________________
2. The FCC sells licenses for broadcast in the FM radio band as 200 KHz channels. Is the broadcast
you are listening to using all of the allotted bandwidth? If not, explain why you think they might
not be.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
__________________________________________________________________
3. Expand the Audio Spectrum display so that you can see it while you are monitoring the signal
view. Describe the behavior of the signal in Db and from the Audio Spectrum display as the
music is playing. How does volume change the shape? How do different sounds appear to
change the shape? Use the waterfall view to illustrate your descriptions.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
RET 2013
5
Information in Radio Waves
4. Describe the peak and the spectrum from the Audio Spectrum view and sketch them in the
space provided. To sketch you might pause the radio for a moment when silence or full music
are happening.
a. When there is silence on the station
Description:
IF Spectrum:
Audio spectrum view
_____________________________
_____________________________
_____________________________
_____________________________
____________________________
b. What does the peak look like when there is a full period of music?
Description:
IF Spectrum:
Audio Spectrum
_____________________________
_____________________________
_____________________________
_____________________________
____________________________
Now explore other stations and compare the strength, the type of spectra , Where the station is
located….
Extension activities:
5. Do you see two smaller peaks on either side of the main peak? If so this means that the station
is broadcasting in stereo. Research stereo transmissions
6. Do you see two rectangular signals on either side of the main peak? If so, this means the station
is broadcasting in HD which is a digital broadcast. Find out what type of information those flat
signals might be carrying.
RET 2013
6
Information in Radio Waves
SDR Project
Part 4: Investigations with a local FM transmitter.
For this activity you will need an FM transmitter like the ones that can be used to broadcast
an IPOD signal to the radio in your car. I recommend this one at amazon
(http://www.amazon.com/gp/product/B005YW0Y3C/ref=oh_aui_detailpage_o01_s00?ie=UT
F8&psc=1)
Procedure
 Get each team of 2 or 3 set up on SDR# and ready to scan for FM stations
 One person or team will be the “hider”.
 Using any device that plays music and that has a headphone jack, They must find a song, a voice
recording, or a phone conversation that they would like to broadcast to the class.
 With the FM transmitter they will select a frequency to broadcast on. This must be a frequency
that is not to close to any other stations broadcast in a region of the spectrum where there is
just static.
 The other groups in the room will try to find that person’s broadcast as quickly as possible.
 Once someone has found the broadcast the hider can move the frequency around by .1 MHz to
demonstrate the change in transmission channel.
Here are some research questions that could be used to develop some experiments with your groups:
 What is the range of the transmitter?
 What objects or materials will interfere with the signal?
 How does the volume affect the spectrum of frequencies received by the tuner?
 Other student generated questions.
Design your own experiment to answer one of these questions. Be sure to make a hypothesis/prediction
in “If_____, then___________, because ____________” format.
Upon teacher approval, carry out your investigation according to your class’s protocols for safety and
accuracy of measurement.
Collect data and illustrate it graphically
Write a report for this experiment
 using the rough draft template found in appendix D
RET 2013
7
Information in Radio Waves
References
http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/\
http://tylerwatt12.com/tips-for-using-sdr/
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html
http://g7jjp-websdr.no-ip.org:8901/
RET 2013
8
Information in Radio Waves
Appendix A : SDR# SoftwareSetup
These instructions are adapted from the blog http://rtlsdr.org/softwarewindows
I followed the automated install instructions for windows:






Go to http://sdrsharp.com/ and download the file sdr-install.zip
Extract the folder and navigate to the sdr-install folder
Double click on the install file – this is a batch file that will set up all the required prorams
The RTL-SDR device driver needs to be installed with Zadig
Running Zadig
o This part can be a little different depending on
your OS and hardware.
o Open Zadig and “allow the program to make
changes to your computer “if asked.
o Under the options menu select ‘list all devices’
o Select the ‘Bulk in interface 0’ option
o Click install driver
Once the the WinUSB driver is installed you are ready to
run SDR# with the RTL-SDR/USB input device.

Find the sdrsharp folder in the newly extracted sdrinstall

Double clickon the sdrsharp.exe file with the icon
RET 2013
9
Information in Radio Waves
Device set up



Under the source menu select the RTL-SDR/USB
Click the gear icon and set the sampling rate to .900001and select the Tuner AGC setting
Now click the play button and tune in to a local FM station.
RET 2013
10
Information in Radio Waves
Appendix B: SDR Project Scoring Rubric: To be handed in with final project.
4
Communicate
includes all
criteria from P
plus:
Fundamental
principles are used
to evaluate the
results of an
original
investigation.
Principles of EM
waves
Principles are used
to inform the
design of an
experiment to test
predicted values of
properties of radio
waves.
Energy of the
system
Experimental
results are
formulated to
make predictions
about energy
requirements or
losses in the
system with
emphasis on
communication
closure.
3
includes all
criteria from BP
plus:
Fundamental
principles are
applied to a line of
inquiry where
original data is
collected and cited
in the report.
External resources
are used to support
discussion.
Principles of waves
are tested with
original
observations of
radio waves from
local resources.
Observations are
analyzed and
compared with
theoretical values.
Energy conversion
is examined
including inputs
and outputs of
energy from the
system of radio
communications
with specific
examples from the
SDR observations.
2
includes all
criteria from LP
plus:
Fundamental
principles are
demonstrated by
descriptions of
observations
made with the
SDR device.
1
Shows the uses of
radio waves
through
observations of a
variety of
sources.
Describe the basic
properties of
waves that can be
used to
communicate
information.
Energy
conversion is
illustrated using
observations of
radio waves.
Basic description of
conversion of
sound energy to
electromagnetic
radiant energy and
vice versa.
Rough draft is
completed and
revised for final
product.
Fundamental
principles are
stated but are not
related to
observations.
Teacher comments:
RET 2013
11
Information in Radio Waves
Appendix D
General Lab Report – Rough Draft Template
Communicating results of an experiment is an important step in the science process. The
following format is derived from standard peer reviewed research journal articles.
Follow the
guidelines closely.
General Considerations:
●
●
●
●
●
●
Each section should be in paragraph format.
Write in the passive voice. Do not use personal pronouns like I, we, he, she, they, our, etc.
Do not use the words it or thing. This will add clarity to your writing.
Every section of the lab should have a header.
Each person must have their own lab report, written in their own words.
YOU MUST CITE ALL OF YOUR RESEARCH SOURCES using in-text citations and include the
full citation at the end of the report in a References section.
● It must be typed via Google Docs to get credit for use of class time and to receive teacher
feedback.
● The final report should be submitted to your teacher through the Turn It In website (turnitin.com).
Components:
1.
Title - Your name, class block, and date in the upper right hand corner.
A descriptive title (not
“Science Lab Report”) should be located in the center of the paper before the introduction.
Your Name:___________________________
Class Block:_____________
Date:____________
Lab Title:______________________________________________
RET 2013
12
Information in Radio Waves
2.
Introduction – Introductory paragraphs are meant to summarize the background information
related to the experiment you are conducting, providing the motivation for your work and putting
it into a broader scientific context (outside references may be used). You will need to state the
purpose, objective and/or research question of the study in this section. If appropriate, the
research question is followed with the experimental hypothesis. Do not summarize the
experiment in the introduction this will occur later in the lab report.
Introduction
with
Background
research
Exceeding (E)
Meeting (M)
In-progress (IP)
Limited
Progress (LP)
Includes all
criteria in Meeting
plus…
Includes all criteria in IP
plus…
Includes all criteria
in LP plus…
Clearly states the purpose of
the paper as it relates to the
class learning objectives or
topic.
Purpose, research
question, and
hypotheses are
stated.
Introduction
states the
purpose,
research
question or
hypothesis of
the
experiment.
The research question is
stated in a testable way.
Hypotheses are in
if…then…because.
.. format.
Background
providing depth
and detail.
Introduction sets
the context of the
experiment with
reference to
theories and
research.
The hypotheses “because” is
reasonable based on general
knowledge and observations.
Introduction:
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
RET 2013
13
Information in Radio Waves
_____________________________________________________________________
3.
Methods – Written in past tense. Summarize the experimental design – numbers of trials,
types of data collected. (For some experiments this requires a description of the independent
variable, dependent variable, constants, and any controls that were used). Describe the basic
procedure including the tools that were used to complete the study/experiment. This should not
be a bulleted list of steps (only appropriate for chemistry). Only include tools or materials that
were specific to this experiment. You do not need to say such basic things as, “a metric ruler
was used to measure the change in length”; all scientists know which tools are appropriate for
measuring length. You should also include a description of the data analysis performed if this is
applicable, i.e. data from each trial was averaged, or collected data was compared with data
from a control. It should flow and be succinct.
Methods
Exceeding (E)
Meeting (M)
In-progress (IP)
Limited
Progress (LP)
Includes all criteria
in Meeting plus…
Includes all criteria in IP
plus…
Includes all criteria in
LP plus…
Methods are
listed.
Procedures are
summarized with
the goal of making
the results
understandable for
the reader.
Experimental design is
detailed stating the
independent and dependent
variables, constants, controls,
and how a high degree of
accuracy is to be achieved.
All methods are
summarized with
mention of measured
variables and
number of trials
Methods:
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
RET 2013
14
Information in Radio Waves
____________________________________________________________________________
4.
Results – The results section contains two subsections:
Data and Analysis
Data - State the observations and data obtained in the lab. In this section you can use data
tables, graphs and lists to convey your data. This section can include both qualitative and
quantitative data. Tables and charts should be accurate, organized and include clearly
labeled column names and SI units of measurement. Each graph or data table must have a
descriptive title and number (i.e. Table 1: Data collected in a closed system, Graph 2:
Change in mass of a chemical reaction over time).
Results:
Data
Exceeding (E)
Meeting (M)
In-progress (IP)
Limited
Progress
(LP)
Includes all
criteria in
Meeting plus…
Includes all criteria in IP plus…
Includes all criteria in LP
plus…
Primary
results are
reported.
Estimates of
accuracy and
error are
reported.
Tables, charts, and graphs
include appropriate labels and
titles. Presentation done neatly
with no errors.
Tables, charts, and
graphs are used to
illustrate basic trends in
the data.
Practice sketches of Graphs, Tables, Diagrams, Charts, etc…below
RET 2013
15
Information in Radio Waves
Analysis - In the analysis you should state any general trends or patterns that are present in the
data, including any values that seem unexpected or highly different from the other values. You
should only state the facts, do not make conclusions. Refer to your data table or graph using one
of two formats: Graph 2 shows… OR …. (Graph 2).
Results:
Analysis
Exceeding (E)
Meeting (M)
In-progress (IP)
Limited
Progress
(LP)
Includes all criteria
in Meeting plus…
Includes all criteria in IP
plus…
Includes all criteria in
LP plus…
The key
results are
stated.
Further analysis is
carried out where
appropriate in
order to test trends
and relationships
References to tables, charts
or graphs using the
appropriate format - Graph 1
shows… or ....(graph 1).
Data is described in
paragraph form
including maximums,
minimums, and overall
trends/comparisons.
Trends are discussed in terms
of the relationship between
variables.
Analysis:
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
RET 2013
16
Information in Radio Waves
____________________________________________________________________________
5.
Discussion & Conclusions - In paragraph form restate the purpose/objective/research
question of the lab and any hypotheses that you were testing. Provide clear statements about how
your data supports or does not support your objective/hypothesis. The more specifics the better.
You should be referencing back to your class lessons to help you make connections between the
data and WHAT the data means. If instructed directly by your teacher put your work into broader
context, how do your research results relate to the larger world (use references)?
Next you should state what problems may have occurred and what changes might be helpful in
clarifying your results. Was there any introduction of error? If so what caused the error. Human
error is not an appropriate description of the error you need to be specific.
To be “Exceeding” in any class: You need to complete all other parts of the discussion and include
any changes to your experiment that might be helpful in clarifying your results. Come up with a
new but related testable research question that would help further your understanding of the topic.
Conclusio
n/
Discussion
Exceeding (E)
Meeting (M)
In-progress (IP)
Limited
Progress
(LP)
Includes all criteria in
Meeting plus…
Includes all criteria in IP plus…
Includes all
criteria in LP
plus…
Results are
discussed
in relation to
the original
purpose or
question.
Suggests a related
testable research
question is provided.
Strengths and
limitations (errors)
and makes valid
suggestions on how
to reduce the error.
Connection back to
hypotheses is correct based
on the results.
Relationship between
variables is discussed,
patterns are logically
explained.
Results are connected back to
and integrated with the
learning objectives or topics of
study from class.
Original research
question and
hypotheses are
presented.
Results are
discussed in
terms of
supporting or not
supporting the
hypotheses.
Discussion__________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
RET 2013
17
Information in Radio Waves
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
__________
6.
References – This section should have a complete list of citations for any resources or
references you used in the writing of your final report. (See the attached sheet and/or Use Easy
Bib.)
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
____________________________________________________________________________
RET 2013
18
Information in Radio Waves
___________________________________________________________________________
Sample References – MLA Citation Style
Book
Okuda, Michael, and Denise Okuda. Star Trek Chronology: The History of the Future.
New York: Pocket, 1993.
Journal Article
Wilcox, Rhonda V. "Shifting Roles and Synthetic Women in Star Trek: The Next
Generation." Studies in Popular Culture 13.2 (1991): 53-65.
Newspaper or Magazine Article
Di Rado, Alicia. "Trekking through College: Classes Explore Modern Society Using the World of
Star Trek." Los Angeles Times 15 Mar. 1995: A3.
Book Article or Chapter
James, Nancy E. "Two Sides of Paradise: The Eden Myth According to Kirk and Spock."
Spectrum of the Fantastic. Ed. Donald Palumbo. Westport: Greenwood, 1988. 219-223.
Junipero Serra High School Dr. Senegar-Mitchell
Website
Lynch, Tim. "DSN Trials and Tribble-ations Review." Psi Phi: Bradley's Science Fiction Club.
1996. Bradley University. 8 Oct. 1997
<http://www.bradley.edu/campusorg/psiphi/DS9/ep/503r.html>.
RET 2013
19