Harold C Fleischer III AE5AS 8262017 1 Ohms Law V I x R Voltage Current x Resistance 8262017 Grounding For Amateur Radio 2 Ohms Law V I x R Voltage Current x Resistance ID: 741005
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Slide1
GroundingforAmateur Radio
Harold C. Fleischer, IIIAE5AS
8/26/2017
1Slide2
Ohm’s Law
V = I x RVoltage = Current x Resistance
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Grounding For Amateur Radio
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Ohm’s Law
V = I x RVoltage = Current x Resistance
V = I x ZVoltage = Current x Impedance
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Ohm’s Law
V = I x RVoltage = Current x Resistance
V = I x ZVoltage = Current x Impedance
V = ((1/C)
∫
i
dt
) + (
i
x R) + ( L x (di/
dt
) )
Voltage = Capacitance divided into the integral of Current over time
+ Current times Resistance + Inductance times the derivative of Current over timeThis equation is why imaginary numbers and polar coordinate mathematics appear in the license examination for Amateur Extra.
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Grounding For Amateur Radio
4Slide5
Battery and Voltage
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Battery
+
-
Voltage
No Impedance
No CurrentSlide6
Basic Complete Circuit
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Battery
+
-
Voltage
Impedance
Current ExistsSlide7
Short Circuit
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Battery
+
-
Voltage
Current
Infinite
No ImpedanceSlide8
Open Circuit
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Battery
+
-
Voltage
No Current
No ImpedanceSlide9
Basic Capacitance Circuit
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Battery
+
-
Voltage
Capacitance
DC – No CurrentSlide10
Basic Capacitance Circuit
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Battery
+
-
Voltage
Capacitance
DC – No Current
Can Current jump the gap in a capacitor?Slide11
Basic Capacitance Circuit
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Battery
+
-
Voltage
Capacitance
DC – No Current
Can Current jump the gap in a capacitor?
Yes, capacitors have a breakdown voltage.Slide12
Can Electrons Jump Air Gaps?
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Battery
+
-
Voltage
Spark Plug
Current
Yes, spark plugs in a car, etc., are all about jumping an air gap to create a spark.Slide13
Lightning Jumps Air Gaps
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When Voltage from static electricity gets high enough, electrons will jump the gap and produce thunder and lightning
+
-
Voltage
Currents will be brief, but very high.
GroundSlide14
Electrons Always Wantto go to Ground
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+
-
Voltage
Ground
Radio Transceiver
+
-
VoltageSlide15
Basic Ground Problem
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Battery
+
-
Voltage
Impedance
Current Exists
-
Ground
V
m
V
c0
V
g
If V
c0
does not equal V
g
, Electrons want to get to ground.Slide16
Basic Electrocution Problem
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Battery
+
-
Voltage
Impedance
Current Exists
-
Ground
V
m
V
c0
V
gSlide17
Basic Grounding Solution
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Battery
+
-
Voltage
Impedance
Current Exists
-
Ground
V
m
V
c0
V
g
V
c0
= V
g
, and you are no longer the best path to ground.
Grounding WireSlide18
Basic Grounding Truth
Grounding is like PregnancyYou are Grounded or you are not Grounded.There is no such thing as partially Grounded.Ideally, you have a Ground when the ground resistance value is 0 ohms.
NEC requires a ground resistance value of <25 ohms.NEC recommends a ground resistance value of 5 ohms or less for sensitive equipment.Type of soil affects what you have to do to get a good ground resistance value.
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Ground Resistance Measurements
Very complicated; not necessarily inexpensive.Must drive ground rod and then other rods to do measurements.Meters can cost upwards of $200-$300.
The default is to follow the NEC.Install ground rods or ground plates.
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Grounding Rods and Plates
Grounding Rod must be:Copper or copper clad aluminum.At least 8’ long with only 3” showing.
At no more than an angle of 45 degrees when driven in.Measuring Ground Resistance is complicated.Mechanical Clamp of AWG 6 copper wire or braid.
(A high current will melt solder.)
Grounding Rod may be placed horizontal in a 30” deep trench if they can not be installed vertically.
Grounding Plate must be:
2 feet square ( 1’ x 1’ x 2 sides).
¼” thick if ferrous, 1/16” thick if non-ferrous.
Hole in center for bolt, nut, and lock washer.
Top of plate must be 5’ below the surface of the ground.
(The more square feet in the plate, the more likely Ground Resistance measurement objectives will be met.)
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Grounding in a House
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Panel
Meter
Black – Hot
White – Neutral
Green - Ground
Grounding Wire
Grounding RodSlide22
Example of a House Ground
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Grounding wire
in protective coverSlide23
Bonding
Bonding is GroundingBonding is tying equipment together to eliminate or dampen inter component electrical interaction: Noise
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Number of Groundsfor your Property
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ONESlide25
Multiple Grounding Rods- One Ground
Shortest Path mattersGround from Meter/Panel goes straight down to Grounding RodGround from Antenna needs to go straight down even if antenna feed cable has to make a turn to the “Radio Shack
Ground from “Radio Shack” needs to go straight downGround from Tower needs to go straight downTie all ground rounds together with AWG 3/0 buried 18” deep.
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Grounding Example
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Grounding Example
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Example of Lightning Arrestor (Surge Protector) at bottom of drip loop.Slide28
Grounding Example Site Plan
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Patio
House
Grounding Rod
Grounding Rod
18” Trench with Grounding Cable
Remember: Number of Grounds on Your Property?
ONE
VHF/UHF Antenna
HF AntennaSlide29
Grounding with Tower Example
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Patio
House
(with no antennas mounted on it)
Grounding Rod
(Radio Shack bonding)
Grounding Rod
(Electrical
Service)
18” Trenches with Grounding Cable
Remember: Number of Grounds on Your Property?
ONE
Tower Bonded to Antenna, Each Leg with Grounding Rod, Leg Grounding Rods 6’ apart, & Leg Grounding Rods joined by Ground Wire 1’ deep
6’Slide30
Emergency Generators
OSHA Fact SheetFrame of portable generator may serve as ground if:Generator supplies only equipment mounted on it or cord connected equipment through receptacles mounted on it.
Non-current metal parts of equipment are bonded to the frame and grounding conductor terminals are grounded to the frame.Do not connect a generator to a structure except through a transfer switch.
Very sensitive situation that may require generator to be grounded.
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Review
You ground to:Protect against an electrical faultProtect against lightningSuppress noise in electrical equipment
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ReferencesARRL Handbook, Chapter 28.1, 91
st Edition, 2014.Silver, H. Ward, N0AX, Grounding and Bonding for the Radio Amateur, ARRL, 2017. Morgan, Jennifer, and
Chusid, Michael, Lightning Protection for the Amateur Radio Operator’s Home, QST, ARRL, June 2017.
CECOM TR-96-2, Earth Grounding Pamphlet, May 1996.
OHSA Fact Sheet: Grounding Requirements for Portable Generators,
DSTM 10/2005.
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