Technician License
Class
Chapter 5
Amateur Radio
Equipment
Computers and Amateur Radio
Most HF & some VHF/UHF stations include a
computer to:
Automate many functions.
Frequency & mode control.
Sending/receiving CW.
Logging & award tracking.
QSL’ing.
Allow types of operation not otherwise possible.
Digital modes.
1
Computers and Amateur Radio
DXLabs Suite
Radio control.
Logging.
QSL’ing.
Award tracking.
DX spots.
Propagation
prediction.
T4A02 -- How might a computer be used as
part of an amateur radio station?
A.
B.
C.
D.
For logging contacts and contact information
For sending and/or receiving CW
For generating and decoding digital signals
All of these choices are correct
2
Transmitters & Receivers
Selecting Band, Frequency and Mode.
Selecting the band.
Usually two or more buttons to select the band.
Several buttons labeled in frequency (MHz), or
Several buttons labeled in wavelength (m or cm), or
1 or 2 buttons (Up & Down).
Transmitters & Receivers
Selecting Band, Frequency and Mode.
Selecting the band.
Frequency
(MHz)
Wavelength
(m or cm)
Frequency
(MHz)
Wavelength
(m or cm)
1.8
3.5
160m
50
6m
80m
144
2m
7
40m
222
1.25m
10
30m
420
70cm
14
20m
902
33m
18
17m
1240
23m
21
15m
2300
13m
24
12m
28
10m
3
Transmitters & Receivers
Selecting Band, Frequency and Mode.
Selecting the frequency.
Tuning knob.
Select frequency.
VFO (variable-frequency oscillator).
Dial-in any frequency within the range of the radio.
Select memory channel.
Most rigs have memory channels you can use to rapidly
select your favorite frequencies.
Keypad.
Direct entry of frequency or memory channel.
Transmitters & Receivers
Selecting Band, Frequency and Mode.
Selecting the mode.
Usually several buttons to select the desired mode.
Often modes are “paired”.
LSB – USB.
AM – FM.
CW – RTTY.
4
Transmitters & Receivers
Control and Function Keys.
Most modern transceivers are rather complex &
have a multitude of settings.
A radio front panel with a multitude of buttons
would not be very convenient to operate.
Manufacturers reduce the number of buttons by:
Using menus to access less-frequently changed settings.
Giving each button or knob 2 or 3 different functions.
Function key or “press & hold” to access 2nd & 3rd functions.
T4B02 -- Which of the following can be used
to enter the operating frequency on a
modern transceiver?
A.
B.
C.
D.
The keypad or VFO knob
The CTCSS or DTMF encoder
The Automatic Frequency Control
All of these choices are correct
5
T4B04 -- What is a way to enable quick
access to a favorite frequency on your
transceiver?
A.
B.
C.
D.
Enable the CTCSS tones
Store the frequency in a memory channel
Disable the CTCSS tones
Use the scan mode to select the desired
frequency
Transmitters & Receivers
Transmitter Functions.
Output power level.
Continuously-variable control.
Most SSB/CW transceivers.
2, 3, or 4 pre-set levels.
Most VHF/UHF FM transceivers.
Microphone gain.
Speech processor.
Common on most SSB transceivers.
Not normally used on FM transmitters.
6
Transmitters & Receivers
Transmitter Functions.
Spurious signals.
§97.3(a)(43) Spurious emission. An emission, or
frequencies outside the necessary bandwidth of a
transmission, the level of which may be reduced
without affecting the information being transmitted.
Transmitters & Receivers
Transmitter Functions.
Spurious signals.
Overmodulation.
SSB & AM.
Too high a microphone gain setting causing distortion.
Results in strong signals outside of the normal 3kHz voice
bandwidth.
a.k.a. – Splatter.
ALC circuit helps prevent splatter.
Reduces peak amplitude of voice signal.
Digital signals are distorted when ALC activates.
7
Transmitters & Receivers
Transmitter Functions.
Spurious signals.
Overdeviation.
FM.
Similar to overmodulation of SSB & AM signals.
Causes excessive bandwidth.
Can cause complete loss of received signal under certain
conditions.
Transmitters & Receivers
Transmitter Functions.
Spurious signals.
RF Feedback.
Can cause spurious signals that sound similar to
overmodulation.
8
Transmitters & Receivers
Transmitter Functions.
Spurious signals.
Key clicks.
CW.
Clicking sounds heard at some distance above and below the
transmit frequency.
Caused by too rapid rise & fall times when carrier is turned on
and off.
Transmitters & Receivers
Transmitter Functions.
Microphones and keys.
Microphones.
Hand microphone.
Usually supplied with transceiver.
Normally has PTT switch.
May have power for auxiliary functions.
Keypad, frequency control, etc.
Desk microphone.
PTT switch on base.
Headset.
Hand switch, foot switch, or VOX for PTT.
9
Transmitters & Receivers
Transmitter Functions.
Microphones and keys.
Microphones.
Commonly used connector types.
8-pin Foster connector.
RJ-45 connector.
a.k.a. – Modular connector.
Even if same type of connector, different
manufacturers wire connectors differently.
Connectors can include other signals.
Push-to-talk (PTT), power, etc.
Transmitters & Receivers
Transmitter Functions.
Microphones and keys.
Keys.
Straight key.
Semi-automatic key.
“Bug”.
Automatic key.
Paddles.
Electronic keyer.
Often built into HF transceivers.
Keyboard.
10
T4A01 -- Which of the following is true
concerning the microphone connectors on
amateur transceivers?
A. All transceivers use the same microphone
connector type
B. Some connectors include push-to-talk and
voltages for powering the microphone
C. All transceivers using the same connector
type are wired identically
D. Un-keyed connectors allow any microphone
to be connected
T4B01 -- What may happen if a transmitter is
operated with the microphone gain set too
high?
A.
B.
C.
D.
The output power might be too high
The output signal might become distorted
The frequency might vary
The SWR might increase
11
T7A07 -- What is meant by term “PTT”?
A. Pre-transmission tuning to reduce
transmitter harmonic emission
B. Precise tone transmissions used to limit
repeater access to only certain signals
C. A primary transformer tuner use to match
antennas
D. The push to talk function which switches
between receive and transmit
T7B01 -- What can you do if you are told
your FM handheld or mobile transceiver is
over-deviating?
A.
B.
C.
D.
Talk louder into the microphone
Let the transceiver cool off
Change to a higher power level
Talk farther away from the microphone
12
T8D10 -- Which of the following can be used
to transmit CW in the amateur bands?
A.
B.
C.
D.
Straight Key
Electronic Keyer
Computer Keyboard
All of these choices are correct
Transmitters & Receivers
Receiver Functions.
AF gain.
Volume control.
RF gain.
Adjusts gain of pre-amp.
Pre-amp needed on higher-frequency bands.
Pre-amp may do more harm than good on lower-frequency
bands.
Sometimes a switch to turn pre-amp on/off or add attenuation.
13
Transmitters & Receivers
Receiver Functions.
AGC speed.
Automatic gain control (AGC) circuit adjusts receiver
sensitivity to accommodate varying input signal strength.
Different modes require different AGC response speeds.
CW & data requires faster response speed.
Voice signals require slower response speed.
Transmitters & Receivers
Receiver Functions.
Squelch.
Silences receiver audio when no signal present.
Carrier squelch.
Silences audio based solely on the absence of an RF signal.
Most effective with FM signals.
Tone squelch.
Silences audio based on the absence of a sub-audible tone.
Continuous tone coded squelch system (CTCSS).
a.k.a. – PL (Private Line®) tone.
Commonly used on VHF or UHF FM repeaters.
14
Transmitters & Receivers
Receiver Functions.
Filters.
Receivers reject unwanted nearby signals by using bandpass filters.
Want to match filter width to bandwidth of signal.
Reduces interference from nearby signals.
Reduces noise level.
Mode
Typical Filter Width
Mode
Typical Filter Width
CW
500 Hz or less
RTTY
500 Hz
SSB
2.4 kHz to 3.0 kHz
Digital
3 kHz to 4 kHz
AM
6 kHz to 8 kHz
FM
15 kHz
Transmitters & Receivers
Receiver Functions.
Receiver incremental tuning (RIT).
a.k.a. – Clarifier.
Allows small changes in receive frequency without
changing transmit frequency.
Transmitter incremental tuning (XIT).
Allows small changes in transmit frequency without
changing receive frequency.
15
Transmitters & Receivers
Receiver Functions.
Noise blanker.
Detects presence of noise pulse & turns off receiver
audio during pulse.
Especially effective on repetitive pulse-type noise.
Ignition noise.
Electric motors.
Fluorescent lamps.
Noise limiter.
Clamps receiver audio at a maximum level.
Transmitters & Receivers
Receiver Functions.
Digital signal processing (DSP).
Nearly all modern transceivers include some DSP.
Convert analog signal to stream of numbers.
Process numbers mathematically.
Convert resulting stream of numbers back to analog signal.
Can perform filtering & other functions not possible
with hardware.
Noise reduction.
Automatic notch filters (ANF).
Adaptive filtering.
16
Transmitters & Receivers
Receiver Functions.
“S” Meter
Measures relative signal strength on a scale from 0-9.
1 “S” unit = 6 dB.
S9 = 50 μV (-73 dBm) at antenna input.
Often derived from AGC signal.
Transmitters & Receivers
Receiver Functions.
Handheld transceivers.
a.k.a. – Handhelds, HT’s.
Typically 2m or 2m/70cm FM.
Can have other bands.
Accessories:
Speaker-microphone.
Belt clip/holster.
AA battery pack.
External antenna.
External power amplifier.
17
T2B02 -- What is the term used to describe
the use of a sub-audible tone transmitted
with normal voice audio to open the squelch
of a receiver?
A.
B.
C.
D.
Carrier squelch
Tone burst
DTMF
CTCSS
T2B03 -- Which of the following describes
the muting of receiver audio controlled
solely by the presence or absence of an RF
signal?
A.
B.
C.
D.
Tone squelch
Carrier squelch
CTCSS
Modulated carrier
18
T4B03 -- What is the purpose of the squelch
control on a transceiver?
A.
B.
C.
D.
To set the highest level of volume desired
To set the transmitter power level
To adjust the automatic gain control
To mute receiver output noise when no
signal is being received
T4B05 -- Which of the following would
reduce ignition interference to a receiver?
A.
B.
C.
D.
Change frequency slightly
Decrease the squelch setting
Turn on the noise blanker
Use the RIT control
19
T4B06 -- Which of the following controls
could be used if the voice pitch of a singlesideband signal seems too high or low?
A.
B.
C.
D.
The AGC or limiter
The bandwidth selection
The tone squelch
The receiver RIT or clarifier
T4B07 -- What does the term “RIT” mean?
A.
B.
C.
D.
Receiver Input Tone
Receiver Incremental Tuning
Rectifier Inverter Test
Remote Input Transmitter
20
T4B08 -- What is the advantage of having
multiple receive bandwidth choices on a
multimode transceiver?
A. Permits monitoring several modes at once
B. Permits noise or interference reduction by
selecting a bandwidth matching the mode
C. Increases the number of frequencies that can
be stored in memory
D. Increases the amount of offset between
receive and transmit frequencies
T4B09 -- Which of the following is an
appropriate receive filter bandwidth to
select in order to minimize noise and
interference for SSB reception?
A.
B.
C.
D.
500 Hz
1000 Hz
2400 Hz
5000 Hz
21
T4B10 -- Which of the following is an
appropriate receive filter bandwidth to
select in order to minimize noise and
interference for CW reception?
A.
B.
C.
D.
500 Hz
1000 Hz
2400 Hz
5000 Hz
T4B12 -- What is the function of automatic
gain control or AGC?
A.
B.
C.
D.
To keep received audio relatively constant
To protect an antenna from lightning
To eliminate RF on the station cabling
An asymmetric goniometer control used for
antenna matching
22
T7A10 -- What device increases the lowpower output from a handheld transceiver?
A.
B.
C.
D.
A voltage divider
An RF power amplifier
An impedance network
All of these choices are correct
Digital Communications
Data Modes.
Amateur transceivers designed for voice
transmission can be used to send digital
information (data) as a series of tones.
Data modes consist of:
Modulation method.
How tones are added to RF signal.
Protocol.
Rules governing how data is converted to tones.
23
Digital Communications
Errors in Digital Modes.
• Error Correction.
• Bit Error Rate (BER).
•
BER = number of bit errors / total number of bits.
• Forward Error Correction (FEC).
•
Adds extra information so that data can be reconstructed.
• e.g. - MFSK-16
• Automatic Repeat Request (ARQ).
•
If error detected, asks sending station to retransmit data.
• e.g. – Packet, Winmor
Digital Communications
Data Modes.
• CW.
• CW is actually a “digital” mode.
• Amplitude modulation (AM).
• International Morse Code.
24
Digital Communications
Amateur Digital Modes.
Radioteletype (RTTY).
Oldest digital mode.
Adapted from land-line teletype system.
Frequency shift keying (FSK).
Audio frequency shift keying (AFSK).
5-bit Baudot code.
Letters A-Z.
No lower case.
Numbers 0-9.
Some punctuation.
Digital Communications
Amateur Digital Modes.
Packet.
Oldest of “modern” digital modes.
Became widely popular in 1980’s.
Still popular on VHF.
1200-9600 baud on 2m.
Not practical on HF.
Limited to 300 baud.
Very slow when band conditions are noisy.
25
Digital Communications
Amateur Digital Modes.
Packet.
Uses AX.25 protocol.
Modified X.25 protocol used for internet.
A “packet” consists of:
Header with routing information & packet number (1-8).
Block of data.
Typically 128 or 256 bytes.
Checksum.
Automatic repeat request (ARQ).
If checksum doesn’t match, asks sending station to repeat.
Digital Communications
Amateur Digital Modes.
Packet.
American Standard Code for Information Interchange
(ASCII).
Start bit.
7 data bits.
Parity bit.
May be 8th data bit.
1, 1.5, or 2 stop bits.
Upper & lower case letters.
Numbers 0-9.
Punctuation & control codes.
26
Digital Communications
Amateur Digital Modes.
PSK31.
Phase shift keying.
31.25 baud.
Narrowest bandwidth of any mode, including CW.
Very effective in noisy conditions.
Digital Communications
Amateur Digital Modes.
MFSK.
Multi-tone frequency shift keying.
Forward error correction (FEC).
Extra information sent to allow reconstruction of original data
in the presence of data.
27
Digital Communications
Amateur Digital Modes.
Olivia.
Variation of MFSK.
Very effective at poor signal-to-noise levels.
S/N = -14 dB.
Relatively slow but robust.
Digital Communications
Amateur Digital Modes.
AMTOR.
Variation of RTTY.
170 Hz FSK.
100 baud.
Special code.
Adds ARQ error correction.
Rarely used anymore.
Replaced by more modern modes.
28
Digital Communications
Amateur Digital Modes.
PACTOR.
Developed by Special Communications Systems GmBH.
Combination of AMTOR & Packet.
PACTOR I.
Open technology Relatively inexpensive modems.
$50.00 to $150.00.
PACTOR II, PACTOR III, & PACTOR IV.
Proprietary technology Very expensive modems.
$1000.00 to >$1600.00.
Used in NTS digital message handling system.
Digital Communications
Amateur Digital Modes.
WINMOR.
Similar to PACTOR.
Developed as inexpensive alternate to PACTOR.
Uses ARQ error correction.
Only a simple soundcard interface is required.
Intended for handling the HF portion of the WinLink
system.
29
T8D01 -- Which of the following is an
example of a digital communications
method?
A.
B.
C.
D.
Packet
PSK31
MFSK
All of these choices are correct
T8D08 -- Which of the following may be
included in packet transmissions?
A. A check sum which permits error detection
B. A header which contains the call sign of the
station to which the information is being sent
C. Automatic repeat request in case of error
D. All of these choices are correct
30
T8D09 -- What code is used when sending
CW in the amateur bands?
A.
B.
C.
D.
Baudot
Hamming
International Morse
Gray
T8D11 -- What is an ARQ transmission
system?
A. A special transmission format limited to video
signals
B. A system used to encrypt command signals to an
amateur radio satellite
C. A digital scheme whereby the receiving station
detects errors and sends a request to the
sending station to retransmit the information
D. A method of compressing the data in a message
so more information can be sent in a shorter
time
31
Digital Communications
Keyboard-to-Keyboard.
2-way real-time digital communications system.
Not for sending data or files.
Nearly all digital modes can be used.
Popular keyboard-to-keyboard modes:
RTTY.
PSK31.
Most popular mode today.
Digital Communications
Automatic Packet Reporting System (APRS).
Packet radio.
144.390 MHz in North America.
Often connected to GPS receiver for position tracking.
Internet.
Often personal weather stations are connected to the internet
for automated weather data gathering.
Gateway.
Ties radio & internet systems together.
32
Digital Communications
Automatic Packet Reporting System (APRS).
Digital Communications
WinLink.
a.k.a – WinLink 2000
Worldwide system for sending and receiving e-mail
over radio.
Modes:
PACTOR III.
WINMOR.
33
Digital Communications
WinLink.
Digital Communications
Setting Up for Digital Modes.
Need some way to:
Convert data to tones.
Feed tones to radio microphone input.
Key the radio.
Receive tones from radio.
Convert tones to data.
Can use:
External modulator-demodulator (modem).
Soundcard software.
34
Digital Communications
Setting Up for Digital Modes.
Modulator-demodulator (modem).
External device to convert data to tones for transmission
and to convert tones to data for reception.
Connects between computer serial port and radio.
Packet Terminal Node Controller (TNC).
Multi-mode controller.
Limited to just a few modes.
Digital Communications
Setting Up for Digital Modes.
Soundcard software.
Computer program that uses computer soundcard to
send/receive the tones.
Requires hardware interface to connect computer soundcard to
radio microphone & speaker connections, and to connect serial
port to PTT.
Some radios have data connector to make connections
easier.
Allows operating all of the various digital modes.
35
Digital Communications
Setting Up for Digital Modes.
Soundcard software.
Digital Communications
Setting Up for Digital Modes.
36
Digital Communications
Gateways.
Provide connections between data transmitted via
amateur radio & the internet.
Message forwarding.
Packet bulletin boards.
WinLink remote message service (RMS) stations.
D-Star repeaters.
CAUTION: All regulations concerning message content &
appropriateness apply to messages sent via internet gateways.
T4A06 -- Which of the following would be
connected between a transceiver and
computer in a packet radio station?
A.
B.
C.
D.
Transmatch
Mixer
Terminal node controller
Antenna
37
T4A07 -- How is a computer’s sound card
used when conducting digital
communications using a computer?
A. The sound card communicates between the
computer CPU and the video display
B. The sound card records the audio frequency
for video display
C. The sound card provides audio to the
microphone input and converts received
audio to digital form
D. All of these choices are correct
T8C11 -- What name is given to an amateur
radio station that is used to connect other
amateur stations to the Internet?
A.
B.
C.
D.
A gateway
A repeater
A digipeater
A beacon
38
T8D02 -- What does the term “APRS” mean?
A.
B.
C.
D.
Automatic Packet Reporting System
Associated Public Radio Station
Auto Planning Radio Set-up
Advanced Polar Radio System
T8D03 -- Which of the following devices
provides data to the transmitter when
sending automatic position reports from a
mobile amateur radio station?
A. The vehicle speedometer
B. A WWV receiver
C. A connection to a broadcast FM sub-carrier
receiver
D. A Global Positioning System receiver
39
T8D05 -- Which of the following is an
application of APRS (Automatic Packet
Reporting System)?
A. Providing real time tactical digital
communications in conjunction with a map
showing the locations of stations
B. Showing automatically the number of packets
transmitted via PACTOR during a specific time
interval
C. Providing voice over Internet connection
between repeaters
D. Providing information on the number of stations
signed into a repeater
T8D06 -- What does the abbreviation PSK
mean?
A.
B.
C.
D.
Pulse Shift Keying
Phase Shift Keying
Packet Short Keying
Phased Slide Keying
40
T8D07 -- What is PSK31?
A. A high-rate data transmission mode
B. A method of reducing noise interference to
FM signals
C. A method of compressing digital television
signals
D. A low-rate data transmission mode
Break
41
Power Supplies and Batteries
Power Supplies.
House power is 120 VAC, 60 Hz.
Most modern radios require +12 VDC.
Actually +13.8 VDC.
A power supply is a device that converts 120 VAC
power to the desired DC voltage or voltages.
Power Supplies and Batteries
Power Supplies.
Unregulated supply.
Simple circuit.
Voltage can vary over a wide range with changing load
current.
Regulated supply.
More complex circuit.
Voltage is nearly constant with changing load.
Radios work best with a regulated power supply.
42
Power Supplies and Batteries
Power Supplies.
Ratings:
Continuous current.
How much current can be supplied over the long term.
Intermittent current.
a.k.a. – Surge current or peak current.
How much current can be supplied over the short term.
Voltage regulation.
How well the power supply can handle rapid current changes.
Power Supplies and Batteries
Power Supplies.
• Regulated Power Supplies.
• Linear.
• Large & heavy.
• Inefficient.
• Generate heat.
• Easy to repair.
• Less expensive.
43
Power Supplies and Batteries
Power Supplies.
• Regulated Power Supplies.
Switching.
Small & lightweight.
Very efficient.
More difficult to repair.
More expensive.
Power Supplies and Batteries
Mobile Power Wiring.
Fuse BOTH positive & negative leads close to the
power connection.
Connect negative lead to negative (-) battery
terminal or to battery ground connection.
Use grommets or sleeves to protect wires where
they pass through firewall.
Do NOT assume that all metal body parts are
grounded.
44
Power Supplies and Batteries
Mobile Power Wiring.
Mobile installations are susceptible to interference
from noise sources not present in home
installations.
Ignition noise.
Present on received signal.
Turn on noise blanker.
Alternator whine.
High-pitched whine that varies in frequency with engine speed.
Present on both received and transmitted signal.
Eliminated by filtering at radio.
Power Supplies and Batteries
Generators and Inverters.
Commercial AC power may not be available.
Emergency operations.
Portable operations.
Generator.
Converts mechanical energy to AC or DC electrical
energy.
Inverter.
Converts DC voltage to AC voltage.
45
Power Supplies and Batteries
Generators and Inverters.
Motor-Generator Sets.
AC generator connected to small gasoline engine.
Old technology.
Less Expensive.
Typically very noisy.
Output voltage not pure sine wave.
Distorted output may damage sensitive electronic equipment.
Power Supplies and Batteries
Generators and Inverters.
Motor-Generator-Inverter Sets.
DC generator connected to small gasoline engine & DC
voltage fed to an inverter.
New technology.
More expensive.
Relatively quiet.
Output voltage is pure sine wave.
Safe for sensitive electronic equipment.
46
Power Supplies and Batteries
Generators and Inverters.
T4A03 -- Which is a good reason to use a
regulated power supply for communications
equipment?
A. It prevents voltage fluctuations from reaching
sensitive circuits
B. A regulated power supply has FCC approval
C. A fuse or circuit breaker regulates the power
D. Power consumption is independent of load
47
T4A10 -- What is the source of a high-pitched
whine that varies with engine speed in a
mobile transceiver’s receive audio?
A.
B.
C.
D.
The ignition system
The alternator
The electric fuel pump
Anti-lock braking system controllers
T4A11 -- Where should the negative return
connection of a mobile transceiver's power
cable be connected?
A.
B.
C.
D.
At the battery or engine block ground strap
At the antenna mount
To any metal part of the vehicle
Through the transceiver’s mounting bracket
48
T4A12 -- What could be happening if another
operator reports a variable high-pitched
whine on the audio from your mobile
transmitter?
A. Your microphone is picking up noise from an
open window
B. You have the volume on your receiver set too
high
C. You need to adjust your squelch control
D. Noise on the vehicle’s electrical system is
being transmitted along with your speech
audio
T5A06 -- How much voltage does a mobile
transceiver usually require?
A.
B.
C.
D.
About 12 volts
About 30 volts
About 120 volts
About 240 volts
49
T6D05 -- What type of circuit controls the
amount of voltage from a power supply?
A.
B.
C.
D.
Regulator
Oscillator
Filter
Phase inverter
Power Supplies and Batteries
Batteries.
One or more battery cells connected in series.
Battery cells create electrical energy through a
chemical reaction.
Primary cell.
Chemical reaction is not reversible.
Cannot be recharged.
Secondary cell.
Chemical reaction is reversible.
Can be recharged.
50
Power Supplies and Batteries
Batteries.
Capacity rated in Ampere-hours (AH) or
milliampere hours (mAH).
500 mAH battery will provide:
500 mA for 1 hour.
50 mA for 10 hours.
25 mA for 20 hours.
5 mA for 100 hours.
etc.
Power Supplies and Batteries
Batteries.
Individual cell voltage depends on materials used
to construct the cell.
Chemistry
Cell Voltage
Type
Lead-Acid
2.1V
Rechargeable
Carbon-Zinc (obsolete)
1.5V
Disposable
Alkaline
1.5V
Disposable*
Nickel-Cadmium (NiCad)
1.2V
Rechargeable
Nickel-Metal-Hydride
(NiMH)
1.2V
Rechargeable
Lithium Ion (LI-Ion)
3.6V
Rechargeable
51
Power Supplies and Batteries
Batteries.
Lead-Acid.
Secondary cell.
Approximately 2.12 Volts per cell.
“12V” battery = 6 cells in series.
Open-Circuit at full charge: 12.6 V to 12.8 V
Open-circuit at full discharge: 11.8 V to 12.0 V
Loaded at full discharge: 10.5 V
Float Charge: 13.8 V
Daily Charge: 14.2 V to 14.5 V
Power Supplies and Batteries
Batteries.
Lead-Acid.
If overcharged will release hydrogen gas.
Remember the Hindenberg!
ALWAYS use in a well-ventilated area!
Gassing threshold ~14.4 V.
52
Power Supplies and Batteries
Batteries.
Sealed lead-acid (SLA).
a.k.a. – Gel-Cell.
Electrolyte is in a gel form rather then liquid.
Sealed so does not vent hydrogen gas.
Avoid over charging to prevent build up of internal
pressure.
Power Supplies and Batteries
Battery Charging.
Some batteries can be recharged, some cannot.
Use the proper charger for the battery being
charged.
Batteries will wear out over time.
Best if batteries are maintained fully charged.
Over-charging will cause heating and could damage the
battery.
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Power Supplies and Batteries
Batteries for Handheld Radios.
Handhelds use battery packs
Packages of several individual batteries connected
together.
Most are rechargeable.
NiCd (nickel-cadmium).
NiMH (nickel-metal hydride).
Li-ion (lithium-ion).
For emergencies, have a battery pack that can use
disposable batteries (usually AA size).
T2C02 -- What is one way to recharge a 12volt lead-acid station battery if the
commercial power is out?
A. Cool the battery in ice for several hours
B. Add acid to the battery
C. Connect the battery in parallel with a
vehicle’s battery and run the engine
D. All of these choices are correct
54
T6A10 -- Which of the following battery
types is rechargeable?
A.
B.
C.
D.
Nickel-metal hydride
Lithium-ion
Lead-acid gel-cell
All of these choices are correct
T6A11 -- Which of the following battery
types is not rechargeable?
A.
B.
C.
D.
Nickel-cadmium
Carbon-zinc
Lead-acid
Lithium-ion
55
T0A09 -- What kind of hazard is presented by
a conventional 12-volt storage battery?
A. It emits ozone which can be harmful to the
atmosphere
B. Shock hazard due to high voltage
C. Explosive gas can collect if not properly
vented
D. All of these choices are correct
T0A10 -- What can happen if a lead-acid
storage battery is charged or discharged too
quickly?
A. The battery could overheat and give off
flammable gas or explode
B. The voltage can become reversed
C. The memory effect will reduce the capacity
of the battery
D. All of these choices are correct
56
RF Interference (RFI)
Radio frequency signals (RF) causing
interference with the proper operation of an
electronic device.
Your transmitted signal can interfere with
electronic devices, even if it is operating properly.
Radio frequency signals generated by electrical
devices can interfere with your receiver.
Higher power more susceptible.
Closer distance more susceptible.
RF Interference (RFI)
Filters.
Used to prevent unwanted signals from being
radiated.
Used to prevent unwanted signals from being
received.
57
RF Interference (RFI)
Filters.
High-Pass -- Passes frequencies above a frequency.
Low-Pass -- Passes frequencies below a frequency.
Band-Pass -- Passes frequencies within a frequency
range.
Band-Reject -- Passes frequencies outside of a
frequency range.
RF Interference (RFI)
Filters.
AC power line filters.
Low-pass filters to prevent RF signals from entering or
leaving a piece of equipment via the power cord.
RF choke.
a.k.a. – Common-mode choke or ferrite choke.
Special type magnetic material (ferrite) placed around a
conductor or cable.
The “lump” in computer cables.
Prevents RF from entering or leaving a piece of
electronic equipment via the cable
58
RF Interference (RFI)
Filters.
RF choke.
RF Interference (RFI)
Direct Detection.
The presence of a strong RF signal can interfere
with an electronic device even if the transmitter is
operating properly.
Often caused by the device acting as a receiver
even when it is not designed to.
Semiconductors in the device can act as diode
detectors.
This is called direct detection.
59
RF Interference (RFI)
Direct Detection.
Telephones.
Direct detection is most common type of RFI.
Install low-pass filter at telephone wall jack.
Install ferrite choke on telephone cord.
Stereos.
Touch-activated lamps.
Electronic doorbells.
RF Interference (RFI)
Overload.
Very strong off-frequency signals can overwhelm
the input stages of a receiver.
Interfering signal may be heard regardless of frequency
(channel) receiver is tuned to.
Problem lies within the receiver.
Add filters to receiver input.
e.g. – Add band-reject (notch) filter to prevent a 2-meter
signal from interfering with broadcast TV.
Adding filters to transmitter will not help.
60
RF Interference (RFI)
Harmonics & Spurious Emissions.
All transmitted signals contain harmonics and
other spurious emissions (spurs).
Goal is to reduce strength of harmonics & spurs as
much as possible.
Good transmitter design.
Proper operation.
RF Interference (RFI)
Harmonics & Spurious Emissions.
Problem lies within the transmitter.
Install low-pass filter or band-pass filter between
transmitter and antenna to reduce harmonics.
Filtering may not reduce strength of spurious emissions
(non-harmonic) if close to transmitter frequency.
Adding filters to receiver input will not help.
61
RF Interference (RFI)
Cable TV Interference.
Interference to amateur receiver.
Interference to TV receiver.
Usually the result of broken shielding somewhere
in the cable.
Loose connections.
Broken connections.
Corroded connections.
Usually solved by proper cable maintenance by
cable supplier.
RF Interference (RFI)
Noise Sources.
Most interference to amateur radio receivers is not
from transmitters, but from “unintentional
radiators”.
Electrical arcs (motors, thermostats, electric fences,
neon signs, etc.).
Power lines.
Motor vehicle ignitions or alternators.
Switching power supplies.
Computers, networks, and TV sets.
62
RF Interference (RFI)
Unknown Signals.
Occasionally may experience interference from a
transmitter inadvertently transmitting in an
amateur band.
Non-amateur transmitter on wrong frequency.
Amateur transmitter accidentally keyed.
Use radio direction finding (RDF) techniques to locate
transmitter.
“Fox hunting.”
RF Interference (RFI)
Guidelines.
Make certain your station is in good working order.
Grounds.
Filters.
Connections.
Use shielded wire and cable where appropriate.
Connect shields properly.
e.g. – Outside of metal equipment enclosures.
Prevents coupling of signals.
Prevents unwanted radiation of signals.
63
RF Interference (RFI)
Guidelines.
Eliminate interference in your own house first.
Eliminate sources of interference in your own
house.
Poorly filtered switching power supplies.
“Wall warts.”
Noisy electric motors.
etc.
RF Interference (RFI)
RFI and Neighbors.
Make certain that your transmissions are actually
the source of the interference.
Offer to help determine the source of the
interference.
If source is in neighbor’s equipment, offer to help
fix it.
You may have to POLITELY inform your neighbor
that they cannot continue to use equipment
causing the interference.
64
RF Interference (RFI)
Part 15 Rules.
Specifies responsibilities of operators of unlicensed
RF devices.
An unlicensed device permitted under Part 15 or an
unintentional radiator may not cause interference to a
licensed radio service.
Operator must prevent the device from causing the
interference or stop using it.
An unlicensed device permitted under Part 15 must
accept interference from a properly operating licensed
communications station.
T4A04 -- Where must a filter be installed to
reduce harmonic emissions from your
station?
A.
B.
C.
D.
Between the transmitter and the antenna
Between the receiver and the transmitter
At the station power supply
At the microphone
65
T4A09 -- Which of the following could you
use to cure distorted audio caused by RF
current flowing on the shield of a
microphone cable?
A.
B.
C.
D.
Band-pass filter
Low-pass filter
Preamplifier
Ferrite choke
T6D12 -- Which of the following is a common
reason to use shielded wire?
A. To decrease the resistance of DC power
connections
B. To increase the current carrying capability of
the wire
C. To prevent coupling of unwanted signals to or
from the wire
D. To couple the wire to other signals
66
T7B02 -- What would cause a broadcast AM
or FM radio to receive an amateur radio
transmission unintentionally?
A. The receiver is unable to reject strong signals
outside the AM or FM band
B. The microphone gain of the transmitter is
turned up too high
C. The audio amplifier of the transmitter is
overloaded
D. The deviation of an FM transmitter is set too
low
T7B03 -- Which of the following may be a
cause of radio frequency interference?
A.
B.
C.
D.
Fundamental overload
Harmonics
Spurious emissions
All of these choices are correct
67
T7B04 -- Which of the following is a way to
reduce or eliminate interference by an
amateur transmitter to a nearby telephone?
A. Put a filter on the amateur transmitter
B. Reduce the microphone gain
C. Reduce the SWR on the transmitter
transmission line
D. Put a RF filter on the telephone
T7B05 -- How can overload of a non-amateur
radio or TV receiver by an amateur signal be
reduced or eliminated?
A. Block the amateur signal with a filter at the
antenna input of the affected receiver
B. Block the interfering signal with a filter on
the amateur transmitter
C. Switch the transmitter from FM to SSB
D. Switch the transmitter to a narrow-band
mode
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T7B06 -- Which of the following actions
should you take if a neighbor tells you that
your station’s transmissions are interfering
with their radio or TV reception?
A. Make sure that your station is functioning properly and that
it does not cause interference to your own radio or
television when it is tuned to the same channel
B. Immediately turn off your transmitter and contact the
nearest FCC office for assistance
C. Tell them that your license gives you the right to transmit
and nothing can be done to reduce the interference
D. Install a harmonic doubler on the output of your transmitter
and tune it until the interference is eliminated
T7B07 -- Which of the following may be
useful in correcting a radio frequency
interference problem?
A.
B.
C.
D.
Snap-on ferrite chokes
Low-pass and high-pass filters
Band-reject and band-pass filters
All of these choices are correct
69
T7B08 -- What should you do if something in
a neighbor’s home is causing harmful
interference to your amateur station?
A. Work with your neighbor to identify the
offending device
B. Politely inform your neighbor about the rules
that prohibit the use of devices which cause
interference
C. Check your station and make sure it meets
the standards of good amateur practice
D. All of these choices are correct
RF Grounding
Electrical Grounding.
Make sure your home is “up to code.”
Most ham equipment does not require special
wiring or circuits.
Use 3-wire power cords.
Use circuit breakers, circuit breaker outlets, or Ground
Fault Interrupter (GFI) circuit breakers.
Use proper fuse or circuit breaker size.
Don’t overload single outlets.
70
RF Grounding
Amateur radio stations require a separate “RF”
ground.
Lack of a proper RF ground can result in:
RF burns when touching equipment while
transmitting.
RF feedback resulting in distorted audio on
transmitted signal.
Erratic operation of computer equipment.
RF Grounding
All equipment should be connected to a
common ground.
Ground should be as short as possible.
Use wide, flat copper strap or braid.
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RF Grounding
Lightning Protection.
Install a separate ground rod
by each leg of your tower.
Do NOT run ground rods
through concrete base.
Ground rods should be
bonded to the tower leg & to
each other.
Connect to station ground.
T4A08 -- Which type of conductor is best to
use for RF grounding?
A.
B.
C.
D.
Round stranded wire
Round copper-clad steel wire
Twisted-pair cable
Flat strap
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T7B11 -- What is a symptom of RF feedback
in a transmitter or transceiver?
A. Excessive SWR at the antenna connection
B. The transmitter will not stay on the desired
frequency
C. Reports of garbled, distorted, or unintelligible
transmissions
D. Frequent blowing of power supply fuses
Questions?
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Next Week
Chapter 7
Licensing Regulations
Chapter 8
Operating Regulations
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