Power Supplies, Batteries, Connectors and Test Equipment

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Power Supplies, Batteries, Connectors and Test
Equipment
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Power Supplies

• Power supplies provide the necessary power,
  voltage and current requirements for electronic
  devices.
• They usually change ac to dc voltage.
• For example, 120 volts ac is changed to 13.8
  volts dc.

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Power Supplies

• Consist of
• Transformer steps ac voltage up or down.
• Rectifier Diodes change ac to bumpy dc.
• Filter Network includes capacitors and
  inductors, smooths out the bumps.
• Voltage Regulator keeps the voltage constant.
• Protection usually a crowbar circuit.

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Power Supply SpecificsHalf Wave Rectifier
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Power Supply SpecificsFull Wave Center-Tapped
Rectifier
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Power Supply SpecificsFull Wave Bridge Rectifier
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Rectifier Comparison
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Rectifiers Half Wave

• Rectifiers are semiconductor diodes that conduct
  in only one direction. Today, most rectifier
  diodes are made of silicon.

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Diode Ratings

• Increase current capacity by putting additional
  diodes in parallel, or by using a diode with a
  larger contact surface area.
• Increase voltage capacity by putting additional
  diodes in series, or by using a diode
  manufactured with a higher voltage rating.
• Use a diode with a voltage rating of at least 1.4
  times the RMS voltage, minimum.

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Power Supply Filters

• Use large coils (called chokes) and capacitors to
  fill in the gaps between ripples in the
  incoming pulsating DC.
• AC hum results from improper filtering.
• Pulling too much current from power supply.
• Failed component (particularly capacitor).
• Plug-in-the-wall power supplies (Wall-Warts)
  generally do not produce high quality DC. They
  may work for some low-current applications
  however.
• Wall-Warts generally produce pulsating DC,
  suitable for charge batteries, and running some
  small devices.

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Filter Network
Capacitors are used in power supply filter
networks. The capacitors smooth out the bumpy
AC to DC.
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Filter Network
Capacitors AND Inductors are used in power supply
filter networks. The inductors aide the
capacitors to smooth out the bumpy DC.
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Electrolytic Capacitor

• Electrolytic capacitors are used to filter
  rectified DC.

• They change bumpy DC to smooth(er) DC.

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Important Concepts

• Half Wave Rectifier
• Simplest.
• Hard to filter well.
• Full Wave Center-Tapped Rectifier
• Easier to filter.
• Requires transformer with center-tap.
• Transformer secondary must be twice intended
  voltage.
• Full Wave Bridge Rectifier
• Easier to filter (just like full wave).
• Center-tap transformer not required.
• Transformer secondary same as intended voltage.
• Higher parts count.

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Power Supply Safety
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Power Supply Safety
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Power Supply Safety

• Grounding is important.
• Connection integrity is important.
• Somewhere neutral and ground are connected
  together.
• Miss-wired hot lead will lead to a hot chassis
  someplace.

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Power Supply Filter Capacitor Safety

• They are charged up to the output voltage of the
  power supply while its in operation.
• Filter capacitors hold a charge a long time.
• Bleeder resistors across the filter capacitors
  bleed off charge when supply is turned off.

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Bleeder Resistors

• A bleeder resistor is installed across the filter
  capacitors as a safety feature to make sure that
  the capacitors are discharged.

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Switching-Mode Power Supplies
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Switching Power Supplies
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Switching Power Supplies

• The advantage of a switching-mode power supply is
  that the relatively high frequency (50kHz-
  150kHz) oscillator allows the use of small,
  lightweight and low-cost transformers.
• This makes them considerably smaller and lighter
  than linear power supplies. Many modern powers
  supplies, including those in PCs, are switching
  mode power supplies. Their disadvantages are
  circuit complexity and their potential for
  radiation of RF interference (at harmonics of
  the oscillator frequency), throughout the RF
  spectrum, to other devices.

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Switching Power Supplies
In a switched mode power supply, the first step
in converting 120 V ac to a 12 V dc output is to
rectify and filter the 120 V.
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Batteries

• Batteries can often be used to provide power for
  your radio equipment when it is inconvenient to
  try to power the equipment from the electrical
  power mains.
• In many cases high-capacity batteries can be
  fabricated to allow portable power to be built
  into your radio. But in some instances, the radio
  may require more power then a small portable
  battery can provide. Thats when a storage
  battery can come in handy.
• All batteries require additional attention from
  the user and must be maintained to in order to
  provide useful service.

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Batteries

• Two basic types (based upon their chemistry)
• Non-Rechargeable Carbon-Zinc, Alkaline, Lithium
• Rechargeable NiCd, NiMH, LiIon, lead acid, etc.
• Battery chemistry determines
• Energy rating (ampere-hours), how much power they
  can provide over their single-charge useful
  life.
• Discharge characteristics, how long they can
  provide useful power during a single-use event.

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Battery Handling/Safety Tips

• Do not attempt to recharge non-rechargeable
  batteries!
• Use only a charger that is designed for that
  particular type of rechargeable battery. Using
  the wrong charger can damage the battery, and can
  cause damage to the user and his home.
• Follow the manufacturers specifications for
  recharging. LiIon cells are particularly touchy
  (can explode) if not properly charged.
• Dispose of spent batteries properly.

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Connectors

• DB-25 or DB-9 connectors are for computer cables.

• Amateur/RF connectors include
• PL-259
• BNC
• N
• A Type N coaxial connector would be a good choice
  to use for 10 GHz feed-line connections.

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Basic Test Equipment

• VOM (Volt-Ohmmeter), orDMM (Digital Multimeter)
• SWR Meter / Wattmeter
• Antenna Analyzer
• Monitor Scope
• Oscilloscope
• Signal Generator
• Noise Bridge
• Field Strength Meter
• Frequency Standard
• Two-Tone Test Generator (for SSB)

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Test Equipment
V-O-M (Analog Multi-Meter)
A Volt-Ohm Meter, incorporating an analog meter
which the user must read in order to obtain
useful information fro the meter. Measurement
range and metering mode selection is provided
by a rotary switch. Accuracy is often /-10 of
the meter reading, not including the users
ability to read the meter itself. A handy tool
for the Amateur.
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Test Equipment
DMM (Digital Multi-Meter)
In use, not significantly different from the
analog V-O-M, other than the fact that the
readout is numeric and tends to possibly imply
a higher accuracy than the meter may be able to
provide. Users tend to trust the implied
high-accuracy of a digital readout more than they
trust an analog meter when they have to read and
interpret the needle position. Also a handy tool
in the shack.
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V-O-M vs. DMM Accuracy
The difference between the accuracy of a V-O-M
(/- 5 to 10), when compared to that of a DMM
(usually /-0.1 to 1) may or may not be of much
importance to the user. When using a meter, many
times the importance of the reading is not the
absolute accuracy, but the difference between
toe readings taken with the same meter. It may
be much more important to know whether reading 2
was higher (or lower) than reading 1, than to
know whether the reading is within 1 of the
intended value. So, while a DMM may give more
accurate readings, the V-O-M may provide just as
usable measurements under certain circumstances.
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Test Equipment SWR and Watt Meter
These devices allow you to keep track of the
degree of match between your transmitter (50
Ohm) output and that of the antenna/feedline
load being provided to the transmitter. They
also allow you to monitor your transmitter
output power.
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Test Equipment Antenna SWR Analyzer
This device incorporates thefeatures of a very
low-powertransmitter and an SWR meterinto a
single, portable, devicewhich can be used to
obtainimportant information aboutthe antenna to
which it is attached.It allows you to tune the
antennawithout transmitting signals harmful to
communications on the same frequency.
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Test Equipment Station Monitor Scope

The station Monitor scope allows you to see
your transmitted signal in real-time. It is
installed in the transmission line so it can
actually look directly at your signal as you
transmit. So if there is a problem with the
signal, you can see the indication and take steps
to fix it before it becomes a problem for others.
The image below, illustrates a single Morse Code
DIT (dot) which has been stopped on-screen
for the operator to examine
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Test Equipment Station Monitor Scope
Sample Monitor Scope RF Envelope Waveforms
Continuous Carrier Input
No RF Signal Input
Morse Single DIT
SSB Voice SIgnal
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Test Equipment Oscilloscope
Oscilloscopes are specialty test devices which
can be of use to the radio amateur in certain
instances. They allow you to look at signals
of all kinds and to use what you see for
analytical purposes. Scopes can be costly, but
can be worth the investment if you have a real
use for them. They are NOT specifically
required for the normal hams shack however.

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Test Equipment Oscilloscope
Using an oscilloscope to compare the values of
two different signal inputs (red and lt. blue,
below).
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Test Equipment Noise Bridge

• Connected between a receiver and an antenna of
  unknown impedance and tuned for minimum noise.
• Can determine characteristic impedance for
  transmission lines.
• Can be used for pre-tuning an antenna tuner.