G4 Amateur Radio Practices

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G4Amateur Radio Practices

• Put out the best possible signal!

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We use a wide array of devices to help us
evaluate our amateur stations.
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An Oscilloscope

• View signal quality
• Contains horizontal and vertical channel
  amplifiers
• This one is analog
• Digital ones exist as well.

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S Meter

• Strength of a received signal
• Calibrated in s units from S1 to S9
• Gives relative signal strengths, because s meters
  vary.

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Field Strength Meter

• Measures strength of an RF field.
• Relative field strength only.
• May be used to detect the field pattern of an
  antenna.
• Direction finding tool as well.

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Signal Tracer

• Trace the path of a signal through a receiver.
• Then you can see which stage of the rig is not
  working properly.

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Noise Bridge

• Antennas must be tuned for maximum performance
• Tune match impedances
• Noise bridge measures impedance of antennas.

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Testing Transmitter Performance

• Two-Tone Test
• Inject two tones into a transmitter.
• ARRL 700 Hz 1900 Hz
• Left Proper TX operation Right Distortion

Oscilloscope Readout
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G4A02 When testing the amplitude linearity of a
single-sideband transmitter, what kind of audio
tones are fed into the microphone input and on
what kind of instrument is the transmitter output
observed? A. Two harmonically related tones
are fed in, and the output is observed on an
oscilloscope B. Two harmonically related tones
are fed in, and the output is observed on a
distortion analyzer C. Two non-harmonically
related tones are fed in, and the output is
observed on an oscilloscope D. Two
non-harmonically related tones are fed in, and
the output is observed on a distortion analyzer
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G4A03 What audio frequencies are used in a
two-tone test of the linearity of a
single-sideband phone transmitter? A. 20 Hz and
20 kHz tones must be used B. 1200 Hz and 2400
Hz tones must be used C. Any two audio tones
may be used, but they must be within the
transmitter audio passband, and must be
harmonically related D. Any two audio tones
may be used, but they must be within the
transmitter audio passband, and should not be
harmonically related
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Power Amplifiers

• A wonderful accessory!
• 600 2000 watts
• But, you dont just hook it up and go!
• Input and Output circuits must be tuned to the
  same frequency.

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Neutralization of Amplifiers

• Stabilizes operation
• Deliberately feed back some of the output 180
  degrees out of phase.
• Negative Feedback
• Positive feedback is cancelled

• Cancels oscillation caused by the effects of
  inter-electrode capacitance

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G4A06 As a power amplifier is tuned, what reading
on its grid-current meter indicates the best
neutralization? A. A minimum change in grid
current as the output circuit is changed B. A
maximum change in grid current as the output
circuit is changed C. Minimum grid current D.
Maximum grid current
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TR Switching

• Transmit-Receive Switch
• Connects to TX during send
• Connects to RX during reception
• Electronic switches are MUCH faster than
  mechanical ones.
• Often uses a diode to switch
• It permits current flow when forward biased and
  blocks current when reverse biased

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G4A04 At what point in an HF transceiver block
diagram would an electronic TR switch normally
appear? A. Between the transmitter and
low-pass filter B. Between the low-pass filter
and antenna C. At the antenna feed point D.
At the power supply feed point
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Peak Envelope Power (PEP)

• SSB rigs transmit no signal when nothing is
  applied to the microphone.
• So the RF envelope produced varies constantly.
• PEP average power of the wave at a peak.

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Power Circle
P
I
E
So, using our algebra, we get
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Power Circle - PEP
P
I
E
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PEP Calculations
What is the Peak Envelope Power from a
transmitter if 200 volts are measured
peak-to-peak across a 50 ohm resistor at the
transmitter output?
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Radio-Frequency Interference (RFI)

• We hams can interfere with lots of electronic
  devices
• Phones
• TVs
• Stereos
• Audio devices rectify (or detect) the RF signal
  and amplify it resulting in interference

Example of FM interference
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RFI -- continued

• Place a filter in line with telephones.
• Make sure all connections are tight
• In your ham station
• In the neighbors home
• Install chokes on coaxial cable
• Ground your equipment!

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G4C02 What should be done if a properly operating
amateur station is the cause of interference to a
nearby telephone? A. Make internal adjustments
to the telephone equipment B. Install RFI
filters at the affected telephone C. Stop
transmitting whenever the telephone is in use D.
Ground and shield the local telephone
distribution amplifier
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G4C03 What sound is heard from a public-address
system if audio rectification of a nearby
single-sideband phone transmission occurs? A.
A steady hum whenever the transmitter's carrier
is on the air B. On-and-off humming or
clicking C. Distorted speech from the
transmitter's signals D. Clearly audible
speech from the transmitter's signals
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G4C04 What sound is heard from a public-address
system if audio rectification of a nearby CW
transmission occurs? A. On-and-off humming or
clicking B. Audible, possibly distorted
speech C. Muffled, severely distorted speech D.
A steady whistling
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Grounding Your Station
All radio station equipment must be properly
grounded, separate from the ground for the
houses AC electrical distribution system. If the
grounding is not kept separate, reflected radio
frequency energy in the form of standing waves
can be conducted into the electrical wiring of
the building and into neighborhood power
distribution lines.
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Grounding Diagram
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Just be careful where you dig!

• Watch for
• Water Mains
• Sewer
• Telephone
• Otherwise, well

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Station Grounding

• Use only copper or galvanized rods
• Eight feet into the ground
• Connect to equipment with copper braid
• Make connections as short as possible!
• Ground ALL your equipment.
• Do not use plumbing for ground.
• Make sure all connections are tight!

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G4C06 Which of the following is NOT an important
reason to have a good station ground? A. To
reduce the cost of operating a station B. To
reduce electrical noise C. To reduce
interference D. To reduce the possibility of
electric shock
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G4C05 If your third-floor amateur station has a
ground wire running 33 feet down to a ground rod,
why might you get an RF burn if you touch the
front panel of your HF transceiver? A. Because
the ground rod is not making good contact with
moist earth B. Because the transceiver's
heat-sensing circuit is not working to start the
cooling fan C. Because of a bad antenna
connection, allowing the RF energy to take an
easier path out of the transceiver through
you D. Because the ground wire is a resonant
length on several HF bands and acts more like an
antenna than an RF ground connection
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G4C09 Which of the following statements about
station grounding is true? A. The chassis of
each piece of station equipment should be tied
together with high-impedance conductors B. If
the chassis of all station equipment is
connected with a good conductor, there is no
need to tie them to an earth ground C. RF hot
spots can occur in a station located above the
ground floor if the equipment is grounded by a
long ground wire D. A ground loop is an
effective way to ground station equipment
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G4C13 How can a ground loop be avoided? A.
Series connect ("daisy chain") all ground
conductors B. Connect the AC neutral conductor
to the ground wire C. Avoid using lockwashers
and star washers in making ground connections D.
Connect all ground conductors to a single point
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Lets talk about RFI central! -- BPL

• Apply RF to power lines (open wires)
• They will radiate
• Just like antennas!
• And you will get interference
• Lets watch a short video about BPL.

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Broadband over Powerline
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Questions?