station grounding final reva

7/31/2019 Station Grounding Final RevA

1/100

Bill LeonardNCURevA

NATC - 285 TechConnect Radio Clubhttp://www.natc.org/

Station Grounding

2/5/2011 1Rev A


2/100

2/5/2011 2

Topics

Electromagnetic Compatibility (EMC)Five Types of Grounds

1. Safety2. Lightning3. Static (DC) Bleed4. Single Point5. RF

AntennaStation

Loops RF Ground

Examples of Real Problems and Solutions

Rev A


3/100

2/5/2011 3

The design process that ensures that the system works as

designedwhen all of the individual boxes are connected as a systemSystem works => no radiated or conducted noise problemsMore than just Radio Frequency Interference (RFI) management

Grounding is an important part of the EMC design processConducted noise is frequently the toughest problem to solve

EMC is EXTREMELYimportant in satellite system designEMC problems cannot always be fixed at the end of a program

$150 M satellite went to the dumpster due to system levelEMC (conducted noise) problems that couldnt be fixed

EMC Engineermust ensure that the entire satellite system works

Few colleges offer any courses on the subjectLearning is mostly by OJT

Electromagnetic Compatibility (EMC)

Rev A


4/100

Ham Station Grounding Very confusing and frustrating subject to research

Complex subject, with numerous variables, and no one solution for all

problems Too many EXPERTS, and they frequently dont agree!

An EXPERT is:

2/5/2011 4Rev A


5/100

2/5/2011 5

Ham Station Grounding Very confusing and frustrating subject to research

Complex subject, with numerous variables, and no one solution for all


An EXPERT is: someone who may be wrong, but is never indoubt

Rev A


6/100

2/5/2011 6

Very confusing and frustrating subject to research Complex subject, with numerous variables, and no one solution for all



Some experts claim no groundof any kind is needed

Use their own personal experience as proof of their beliefs One expert in So. Cal. claims that anyground is a waste of time and

money

He has never had any damage from a lightning strike in over 10 years ofoperating

There have been no reports of a lightning strike in the area where he lives formore than 16 years

Ham Station Grounding

Rev A


7/100

2/5/2011 7






money



Some experts (W8JI) claim that a GOOD ground is all thatis needed

The cell phone industry still loses 50 sites (0.01%) a year due to lightning

W8JIs GOOD ground can cost more than a good transceiver

W8JI has a lot of good info on his website, but I dont always agree with him

www.w8 i.com


Rev A


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2/5/2011 8






money



Some experts (W8JI) claim that a GOOD ground is all that isneeded The cell phone industry still loses 50 sites (0.01%) a year due to lightning

W8JIs GOOD ground can cost more than a good transceiver

W8JI has a lot of good info on his website, but I dont always agree with him

www.w8 i.com


Rev A


9/100

Station Grounding is a SYSTEM DESIGNIssueThere are at least FIVETypes of grounds (in order of importance)

1. Safety

MUSThave to prevent dangerous 60 Hz voltages from occurring acrossany two different ground points

National Electrical Code (NEC) requirement

2. LightningShouldhave to dissipate surge energy before it can enter the house

3. Static (DC) BleedShouldhave to dissipate any static charge on antenna to ground, befor

connecting to any receiver

4. Single PointShouldhave for mitigation of any problem loops

5. RF (two types)

Antenna:May, or may not be needed:Balanced vs. unbalanced antennasTo achieve the correct antenna feed impedanceTo achieve maximum radiation efficiencyDoes notsignificantly affect radiation pattern

2/5/2011 9Rev A


10/100

Station Grounding is a SYSTEM DESIGNIssueFIVETypes of grounds (continued):

2/5/2011 10

The only ground that you MUSThave is a SAFETY

ground!Rev A


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Why Are Grounding Problems So Difficult To Solve?

1) There is a conflict between the two different design constraints:

Safety: Grounding to prevent electrical shockNoise: Grounding to eliminate unwanted electronic noiseThese two constraints are often not compatible, and their designsolutions are frequently in direct conflict

Safety ALWAYS wins

There is always a certain amount ofresistance and inductance in evepath to any grounding point

Even if you can get to it (RF-wise), Earth may not be very good RF-wise

2) There is NOabsolute ground

2/5/2011 11Rev A


12/100

N0CU Station Grounding

Granite Rock

SINGLEPOINT

GROUND

Floating HF Beam

48Rohn 25

40M

Vertical

LIGHTNINGGROUND 2

RadioEquipment

STATIONRF

GROUND

ACMains

BreakerBox

Ground (dirt)8 ft

ACAntenna

SwitchBox

RadioEquipmentRadio

Equipment

AC

SVLSAFETYGROUND

Rotator

SVL

TOWERRF

GROUND

SVL= Surge Voltage Limiter

~5 ft

TOWERLIGHTNINGGROUND

2/5/2011 12Rev A


13/100

1. Safety Ground

ALL grounds must be connected to AC Mains ground (the Safety GrounUsually an 8 ft ground rod at AC Mains entrance box

This is a NEC requirementThis is the one point that all experts agree uponBe cautious when using isolated AC grounds

2/5/2011 13Rev A


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2/5/2011 Rev A 14

Isolated Grounds

Two types of AC Power Grounds:Isolated Ground (IG)

Noise reductionEquipment Ground (EG)

SafetyShould never carry current

This is only true in an ideal power system that will never see a fauThe (EG) needs to be able to carry enough current to cause

the circuit breaker/fuse to open during a fault

120VAC

Power

Hot (H)

Neutral (N)

Standard 120V ReceptacleStandard Primary Power:

120VAC

OutletEquipment Ground (EG)

BlackWhite

Green Wire

Also connected to Earth ground


15/100

2/5/2011 Rev A 15

Uninterruptible Power System (UPS) Grounds:

IN

EG

H

EG

N

Standard Ground:

H

EG

NIN

IG

IG Receptacle

Isolated Ground (IG):

EG

Standard120V

Receptacles

To StandardReceptacles

120VAC

Power

120VAC

Output

120VAC

Power


16/100

2/5/2011 Rev A 16

In most cases, an Isolated Ground (IG) is a waste of

money. IEEE 1100, Powering and GroundingSensitive Electronic Equipment (Emerald Book)states, "The results from the use of the IG methodrange from no observable effects, the desired effects,

or worse noise conditions than when standardequipment bonding configurations are used to serveelectronic load equipment [8.5.3.2].

Equipment that is totally isolatedfrom Earth Ground(EG) is dangerous and can cause injury or death.....There are some reasons to use an isolated grounddue to ground loops, but one socket needs to be asolid earth ground.

Isolated Grounds


17/100

Lightning Generation

Many different types of lightning

Watch out for this one!

2/5/2011 17

+-++

--

Rev A


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A lightning bolt can be eitherpositive or negativeNegative bolts most common (95%)

Streamerdown (invisible) and then the big strike up (visible)

Strike Duration: significant energy up into the MHz range)Voltage Gradient:

Pre-strike:pre-ionized path voltage can be >3 megavolts/meterPost-strike: ionizedpath voltage is several hundred volts/meter

Current:Most strikes are in the range 5,000 to 20,000 ampsThe most powerful lightning strike ever recorded in the United States discharged

approximately 345,000 ampsPower per strike:

Peak power: ~1 trillion watts

Energy: ~500 megajoules (~100 W light bulb for 3 months)Air Temperature: ~30,000 oFSolder instantly vaporizes

Grounded metallic objects dominating the area are more likely to be struck bylightning than the surrounding ground or lower structures nearby. This is why:

Lightning rods work

Towers/vertical antennas are more likely to be struck

Some facts about Lightning

2/5/2011 18Rev A


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2. Lightning Ground

Multi-Level Protection:

Distribute the energy over a number of different ground pointsFirst Level (when possible):At the likely strike point (tower, vertical, etc)

Last Level:Just outside the entrance to shack or house

Two levels used at N0CUFirst level is at the tower

Second level is on the outside, at the entrance into the house

2/5/2011 19Rev A


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2/5/2011 20

Non-Floating HF Beam

Tower

LIGHTNINGGROUND 2 Ground (dirt)

Antenna

SwitchBox

SVL

SVL

12/1/2010 20

Assumptions:Antenna is at same highvoltage

as the top of the tower

Base of tower is at ~0 voltsGuideline:Ground reference antennato

tower base (via an SVL)

Metal Boom


Common Antenna Ground

Rev A

Common

Mode

Choke

Balun orChoke?

Antenna SurgeProtected toTower Base

Short toGNDwhenOFF

LIGHTNINGGROUND 1


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2/5/2011 Rev A 21

Floating HF Beam

Tower

LIGHTNINGGROUND 2

Ground (dirt)

Antenna

SwitchBox

SVL

~5 ft

Assumptions:Lightning strike will hittower,

not antenna

Antenna will be at asignificantlylower voltage than the top

ofthe tower

Base of tower is NOTat 0

volts

FiberglassBoom


N0CU Antenna Ground

Common

Mode

Choke

Balun

Granite Rock


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2/5/2011 22

Floating HF Beam

Balun

To Radio

TOWERGROUND

LIGHTNINGGROUND 2

SVL

AntSW

RadialGround

Impedance=ZGND1

STATIONGROUND

Earth Ground

CommonModeChoke

INSULATOR

RSTA

LSTA

RGND2

LGND2

Shield

Rev A

RGND1

LGND1

N0CU Isolated Antenna GroundVSTRI

KEVCOUPLE

D Assumptions:

Lightning strike will hittower,

not antennaAntenna will be at asignificantly

lower voltage than the topof

the tower Base of tower is NOTat 0volts


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2/5/2011 23

CommonModeChoke

TOWERLIGHTNINGGROUND

RTOWER

LTOWER

RCOAX +RBAL

LBAL

VSTRIKE

VCOUPLED

VC

ZTOWER

RGND1

LGND1

RGND2

LGND2ZGND1

VS

To Radio

RSTA

LSTA

STATIONGROUND

Earth Ground

Tower

LIGHTNINGGROUND 2

AntSW

SVL

Shield

Rev A

N0CU Isolated Antenna Ground

My Assumptions:Antenna line is grounded at AntSW

Z (Coax) >> Z (Tower) Strike will hit Tower(not antenna)

VSTRIKE >> VCOUPLEDZGND1 > ZT

Vs ~ VSTRIKEVC > 0Vs >> VC

Keep antenna isolated from tower

VSTA+1000

VGND=0 v

VSTA=?v


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1/18/2011 24

RGND2

LGND2

To Radio

RSTA

LSTA

Earth Ground

AntSW

SVL

Rev A


My Assumptions:Decisions driven by Common Mode

Antenna line is grounded at Ant SWZ (Coax) >> Z (Tower) Strike will hit Tower(not antenna)VSTRIKE>>VCOUPLED

ZGND1 > ZTVs ~VSTRIKE

VC


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2/5/2011 Rev A 25

RGND2

LGND2

To Radio

RSTA

LSTA

Earth Ground

AntSW

SVL


My Assumptions:Decisions driven by Common Mode

Antenna line is grounded at Ant SWZ (Coax) >> Z (Tower) Strike will hit Tower(not antenna)VSTRIKE>>VCOUPLED

ZGND1 > ZTVs ~VSTRIKE

VC


26/100

2/5/2011 Rev A 26

Rotator Grounding???

Granite Rock

Floating HF Beam

48Rohn 25

ACMains

BreakerBox

Ground (dirt)8 ft

AntennaSwitch

Box

RotatorController

AC

SAFETYGROUND

Rotator

SVL


~5 ft

1/18/2011 26Rev A

VGND1

VGND1 +/-82V


27/100

Tower/Vertical Grounding - Lightning

Brute Force** Distributed

More=Better

8 ft

gndrods*

Tower/Vertical

16 ft spacing

Large (0 to 00) cable(use clamps)

Tower/Vertical

Medium (#6) cable>16 ft long

*Can be difficult to get 8 ft down**May not work well with poor ground conditions


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2/5/2011 28

Tower/Vertical Grounding - RF

More=Better

Distributed

Tower/Vertical

Small (#18) cable*1/8 to 1/4 longUp to 120Above or below ground

*Galvanized chicken wire also works well

Counterpoise

Tower/Vertical

Small (#18) cableSpecified lengthIsolated aboveground

Up to 120

Rev A


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W8JI Hybrid Tower Ground

2/5/2011 29

Hybrid approach combines some of brute force, and some of distributed

Rev A


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2/5/2011 30

W8JI Hybrid Tower Ground

Brute Force (Copper strap is best)

Daisy Chained distributed radials:Not the best for RFPoor for lightning

Solder connection???

Weak link for

Lightning

Rev A


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N0CU Tower Ground (Distributed)

Chicken wire:Favor northern hemisphere

3 lengths2 ft wide33 ft long

Copper radials:Favor northern hemisphere5 lengths

37 ft #14 copper

Copper radials:Equally spaced15 lengths

15 ft #6 copper

Copper radials:Favor northern hemisphe

6 lengths22 ft #14 copper wel

Copper ring:At base of tower in copper tubing

Tower

2/5/2011 32

Both Lightning and RF ground needed

Rev A


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N0CU Tower Ground (continued)

Granite base

Matching Networkfor 40 M Vertical

2/5/2011 33Rev A


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N0CU Tower Ground (continued)

2/5/2011 34

New chicken wire is surprisingly easy to solder

Rev A


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W8JI Good Ground at Shack Entrance Point

2/5/2011 35Rev A


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2/5/2011 36

N0CU Ground at Shack Entrance Point

SVL

Antenna switch

Lightning Ground 2

Safety Ground

Cheap current choke

Rev A


37/100

3. Static Ground

10 M 10 M

10 M

What does notwork!

10 M

What works!

10 M

Conn Conn

To Antenna

To Antenna

Even a 2 M beam can build up enough voltage to jump the gap on a

PL-259 connector!

2/5/2011 37

To Antenna

All static charge must be bled to ground!

Antenna

Rev A


38/100

4. Single Point Ground (SPG)

SPGs are used to:Reduce the effects of audio/RF loops

SPGs do noteliminate loopsImprove effectiveness of AC line filters

Satellites are designed to have


39/100

2/5/2011 Rev A 39

5. RF Grounds

What is meant by Ground?:an electrical connection to Earth,

For lightninga third conductor in a power distribution system,

For safetya common return point within a circuit or piece equipment,the RF return" for an unbalanced antenna like a vertical or a

singleended longwireRF return for common mode currents induced into an antennafeedline?

Even a good Ground is nota "sink" into which all unwantedRF andnoise can be poured, never to bother us again

An electrical connection to an Earth ground is rarely part ofa

solution to RF or noise problems


40/100

Antenna RF ground:Needed forUnbalanced antennas (ie, ground mounted verticals):

A good RF ground is needed to optimize match & efficiencyOnly affects the near field performance (match & efficiency)

Near Field is 1 to 10+ wavelengths from the antennaDoes not affect the pattern

Distributed set of radialsAbove ground (counterpoise)

Radials may need to be tuned for a given bandBetter for RFWorse for lightning

Below groundBetter for lightningWorse for RFCorrosion?

A ground rod is not an effective RFgroundA Balanced antenna should not need a good ground in thenear field

5. RF Grounds

2/5/2011 40Rev A


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2/5/2011 41

5. RF Grounds

Rev A


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2/5/2011 Rev A 42

Station RF Ground

Small (#18) cable*1/8 to 1/4 longUp to 120 radialsOn or below ground

*Galvanized chicken wire also works well

RF Ground Resistance vs Number of Radi# Ohms2 28

30 12120 7


43/100

2/5/2011 43

Some Symptoms of RF-In-The-ShackMicrophone bites (nasty RF shock, usually on the lips)

Gritty and or fuzzy transmit audio modulation (distortion)

Malfunction of electronic keyer (sending wrong characters)RF shock when touching metallic objects within the shackPower supply jitters (the regulated power supply becomes un-regulated!)Crazy SWR meter readings

Readings that vary as your hand is moved over some equipment

Desktop computer going crazyPC Desktop monitor jittersFluorescent lamp flickerLamps that INCREASE in brightness when transmittingActive TTL switch circuit going crazy (turning ON-OFF-ON by itself)Inactive panel meters of separate equipment moving on their ownWhen transmitting, a distorted audio is heard over the amplifiedspeaker of the PC desktop

Radio Frequency Interference (RFI)

Rev A


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2/5/2011 44

Antenna feedlines that have high levels of "common-modecurrent

Antennas that are too close to the operating positionA common rule-of-thumb for HF antennas is 100 feetfromstation

Equipment with improperly designed/defective:Enclosures

InterconnectionsInput or output portsInternal grounding

Some Causes of RF-In-The-Shack Problems

Rev A


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2/5/2011 45

Common Mode Current

AC MainsGround

Ideal Dipole

SPG

NoCommon

ModeCurrentRadio

V=0

Rev A

Ideal Balanced Line

Ground

Green wire


46/100

2/5/2011 46

Common Mode Current

AC MainsGround

Unbalanced Dipole

SPG

CommonMode

Current

Common

ModeCurrent

Radio

V= IxZ

Rev A

Actually, any dipole fed directly with coaxis a TRI-Pole, which can produce high levof Common Mode Current on the feedline.

Determined byCommon

Mode CurrentAND

Impedance to Ground

Ground

Common

ModeCurrent


47/100

Station RF Ground

AC MainsGround

Station RF Ground

SPG

2/5/2011 47

=>

Z=

RsL10 ft

CommonMode

Current

Radio

Rev A

Ground

CommonMode

Current

Unbalanced Dipole


48/100

2/5/2011 48

RF Impedance of a Wire

Inductance of a non-resonantstraight wire:

For10 ftof0.2 in diameter cable:

L = 4.3 uH

Inductive Reactance (ohms)

MHz

Rev A


49/100

2/5/2011 Rev A 49

RF Impedance of a Wire

Inductance of a non-resonantstraight wire:

For10 ftof0.2 in diameter cable:

L = 4.3 uH

Inductive Reactance (ohms)

MHz

Non-resonant implies: Length < 1/10


50/100

2/5/2011 50

Impedance of a straight wire connected to ground:

Z ()

Frequency

Z=2fL

lengths:16 @ 29 MHz

34 @ 14 MHz134 @ 3.5 MHz

Rev A

lengths:8 @ 29 MHz

17 @ 14 MHz67 @ 3.5 MHz


51/100

2/5/2011 51

Radio

Station RF Ground

=>

=>

Rs

Rs

Resonant Ground

CommonMode

Current

L

Capacitor is chosen to resonate with L

C

Rev A

Unbalanced Dipole

Ground

SPG

G


52/100

2/5/2011 Rev A 52

Radio

=>

=>

Rs

Rs

CommonMode

Current

L

C

Resonant Ground

A

Unbalanced Dipole

Ground

SPG

Station RF Ground

Capacitor is chosen to resonate with L

A tifi i l G d


53/100

2/5/2011 53

Radio

A

=>

Artificial Ground = GroundTuner

=>

Rs

Rs

Artificial Ground

CommonMode

Current

L

C

Rev A

Unbalanced Dipole

Ground

SPG

Station RF Ground

A tifi i l G d


54/100

2/5/2011 54

Radio

A

=>

=>

Rs

Rs

Artificial Ground

CommonMode

Current

Max voltage point

L

C

Most of the Common ModeCurrent

is dissipated in the ground as

heat Rev A

Artificial Ground = GroundTuner

Unbalanced Dipole

Ground

SPG

Station RF Ground

A tifi i l G d


55/100

2/5/2011 55

Radio

AMFJ-931ArtificialGround

Artificial Ground

CommonMode

Current

C

Counterpoise


56/100

2/5/2011 Rev A 56

Impedance of an open-ended straight wire:

Z ()

Frequency

Z=2

fL

lengths:8 @ 29 MHz

17 @ 14 MHz67 @ 3.5 MHz

A tifi i l G d


57/100

2/5/2011 57

Radio

AMFJ-931ArtificialGround

Artificial Ground

CommonMode

Current

Max voltage point

C

MFJ Operation Manual Caution Note:

Counterpoise


58/100

2/5/2011 Rev A 58

MFJ-931 Artificial Ground

Ch k /B l B tt S l ti th St ti RF G


59/100

2/5/2011 59

Choke/Balun = Better Solution than a Station RF Groun

AC MainsGround

SPG

LowCommon

ModeCurrent

Radio

Balu

nStationGround

NotNeeded?

=>

Baluns & Current chokes do noteliminateCommon

Mode Currents, they reduce them to a lowerlevel

Rev A

Unbalanced Dipole

Ground

St ti RF G d


60/100

Station RF Ground

Bottom Line:Since most, but not all, RF-in-the-shack problems are caused byimproperantenna implementation:

Maintain balanced (or unbalanced) impedances at all interfacesMaintain adequate separation between antennas and station equipment

The quality of the RF ground is usually not the primary issue

The best cure for RF-in-the-shack problems:Keep all equipment at the same potential (ie, a good SPG), andKeep all unwanted RF currents outside the shack

2/5/2011 60Rev A

L


61/100

2/5/2011 61

Loops

Circuit Loops always exist (by definition)GOOD Loops vs. BAD Loops

Problems with Loops can arise when:1) Two or more Loops share a common impedance, andthere isa current flow that generates a common voltage in thosecircuits

Usually more of a problem at low frequencies

2) There is sufficient Loop AREA to pickup interfering RFsignalsUsually more of a problem at high frequenciesThe larger the Loop, the greater the chance of a problem

Unwanted Ground Loops almost always exist, but dontalways

cause a problemA Ground Loop is defined as ???

A circuit with more than two connections to Ground

Problem Loops dont always involve a Ground LoopRF Feedback is frequently assumed to be the cause of

distorted Rev A

Loops (continued)


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2/5/2011 62

CircuitA

+

- CircuitB

+

-CircuitLoop 1

Ground

CircuitLoop 2

Two isolated LoopsNo unwanted coupling

Loops (continued)

Rev A

HighCurrentCircuit

Loops (continued)


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2/5/2011 63

CircuitA

+

- CircuitB

+

-CircuitLoop 1

Ground

CircuitLoop 2

Two connected LoopsNo unwanted coupling

Loops (continued)

Shared common impedance,but no current flow

Current flow requires a closedloop around a voltage source

Rev A

Loops (continued)


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2/5/2011 64

CircuitA

+

- CircuitB

+

-CircuitLoop 1

Ground

CircuitLoop 2

Two connected Loops connected to groundNo unwanted coupling

Loops (continued)

Shared common impedances,but no current flow

Each circuit has only ONE path to ground

Rev A

PS

Loops (continued)


65/100

2/5/2011 65

CircuitA CircuitBCircuitLoop 1

Ground

CircuitLoop 2

Two Mutually Coupled Loops with a Ground LoopPossible problems from any/all of three sources

Division of circuit return currentsLoop antenna for RF pickupInjection of noise voltages from ground currents

Loops (continued)

GroundLoop

Ideally, no circuit has more than one path to ground!(Rarely achievable)

Rev A

+

-PS

+

-PS

Loops (continued)


66/100

2/5/2011 66

To mitigate problems:OPEN the loop

Sometimes used in audio and low frequency circuitsNot a good approach for RF applications

Loops (continued)

CircuitA CircuitBCircuitLoop 1

Ground

CircuitLoop 2

Rev A

+

-PS

+

-PS

Loops (continued)


67/100

2/5/2011 67

To mitigate problems:ISOLATE signal paths from ground noise

CircuitA

+

- CircuitB

+

-CircuitLoop 1

Ground

CircuitLoop 2

Single Point Ground (SPG)

Loops (continued)

I dont consider this loop a Ground Loop.To me, it is a Grounded Loop.

Rev A

Loops (continued)


68/100

2/5/2011 68

To mitigate problems:ISOLATE signal paths from ground noise and unwanted coupledsignals

Choke solution is hard to implement for low frequency noise

CircuitA

+

- CircuitB

+

-CircuitLoop 1

Ground

CircuitLoop 2

SPG

Loops (continued)

Choke

Rev A

Low Frequency (Audio) Ground Loops


69/100

Mic

0-10 Amps

XCVR

Audio

XCVR

(1-10 mV)

PowerSupply

+

-

2/5/2011 69

With SSB transmissions, this current varies with modulation


Rev A



70/100

MicAudio

EQ

0-10 Amps

XCVR

Audio

Noise

XCVR

(1-10 mV)

(? mV)

PowerSupply

+

-

2/5/2011 70

CircuitLoop1


CircuitLoop2

Rev A



71/100

2/5/2011 Rev A 71

Mic

XCVR


The Pin 1 Problem:

Well known in the Audio communityCommon problem in some older Ham gear

AudioCircuit

Cable shield should beconnected directly to chassis



72/100

2/5/2011 Rev A 72

Mic

XCVR


AudioCircuit

The Pin 1 Problem:

Well known in the Audio communityCommon problem in some older Ham gear



73/100

2/5/2011 Rev A 73

Mic

XCVR


AudioCircuit

RFC/FB

For Problems with RF Pickup, try a Ferrite Bead or RF Choke



74/100

Mic XCVR

Audio

Noise

XCVR

(1-10 mV)

(? mV)

PowerSupply

+

-

2/5/2011 74

Uncontrolledreturn pathfor audio signal

AudioEQ

To mitigate problem, try opening one end of the shield on the audio cablIn satellite design, only RF cables are grounded at both ends!

At Lockheed/Martin, a corporate VP must approve any exception


Rev A

0-10 Amps



75/100

2/5/2011 75

Mic XCVR

PowerSupply

+

-

AudioEQ

Is there still another potential problem area?


Rev A

0-10 Amps



76/100

2/5/2011 76

Mic XCVR

PowerSupply

+

-

AudioEQ


Both currents flowing thrua common impedance


Rev A



77/100

2/5/2011 77

Mic XCVR

PowerSupply

+

-

AudioEQ

Possible solutions for this problemare:

Improve DC voltage regulationImprove DC voltage filtering

Minimize common impedance

Low Frequency (Audio) Ground LoopsBoth currents flowing thrua common impedance

Rev A



78/100

2/5/2011 78

Mic XCVR

PowerSupply

+

-

AudioEQ


Common impedanceminimized

Rev A



79/100

2/5/2011 79

Mic XCVR

PowerSupply

+

-

AudioEQ


q y ( ) p

Rev A



80/100

2/5/2011 80

q y ( ) p

Both currents flowing thra common impedance

Mic XCVR

PowerSupply

AudioEQ

+

-

Rev A



81/100

2/5/2011 81

Mic XCVRAudio

EQ

q y ( ) p

PowerSupply

+

-

Still have two Loops, but thecommon impedances have been

minimized Rev A



82/100

2/5/2011 82

Mic

XCVR

PowerSupply

+

-Balanced, differential line with twisted, shielded pair is the bestsolution

Rarely used in Amateur equipment

Shield

Audio Signal-

Audio Signal+

AudioEQ

Audio

Noise

XCVR

(1-10 mV)

(?mV)

SPG0-10 Amps

q y ( ) p

Rev A



83/100

2/5/2011 83

MicXCVR

PowerSupply

+

-

Separate grounds are used in newer Amateur equipment

Audio Gnd

Audio Signal

0-10 Amps

q y ( ) p

Rev A

Shield

Audio Ground Loops- 2 Tone Test on TS-130S


84/100

2/5/2011 84

Carrier at 14.175 MHz and 100 watts output

p

SpectrumAnalyzer

50 Load

1 ToneGenerator120

VAC1 Tone

Generator

SUM TS-930S

12VDC

PS

Rev A



85/100


SpectrumAnalyzer

50 Load

1 ToneGenerator120

VAC1 Tone

Generator

SUM TS-130S

2/5/2011 85Rev A

12VDC

PS



86/100


2/5/2011 86Rev A

SpectrumAnalyzer

50 Load

1 ToneGenerator120

VAC1 Tone

Generator

SUM TS-130S

12VDC

PS



87/100

SpectrumAnalyzer

50 Load


2 ToneGenerator

TS-130S9VDC

Battery

Elecraft2T-Gen

2/5/2011 87

Isolated generator

Rev A

120VAC

12VDC

PS

Loop Antenna


88/100

2/5/2011 88

Loop Antenna

Receiver

Rev A

RF Loop


89/100

2/5/2011 89

Loop Antenna

Receiver

Loop Antenna

VoltageLength

Rev A

RF Loop


90/100

2/5/2011 90

Loop Antenna Loop Antenna

VoltageLength

Grounded Loop Antenna

Receiver

Rev A

The larger the LoopAREA, the better the Antenna

Unwanted Loop Antennas


91/100

2/5/2011 91

Unintentional loop antenna can pick up unwanted Electromagnetic energyTo eliminate => RF ISOLATE the loop

Xcvr

Shielded cables do notprovide 100%shielding

Mic

AudioEQ

3 Loop Antennas

Rev A

GroundedLoop

Problem Loops at N0CU


92/100

2/5/2011 92

Mic

AudioAmplifier

RFAmplifier

TS-930STransceiver

120VAC

Rev A

Problem Loops at N0CU


93/100

2/5/2011 93

RFAmplifier

Mic

At least 7 Loop Antennas

AudioAmplifier

TS-930STransceiver

120VAC

Rev A

21 turns shielded cable over 1 large ferrite toro

Fixes for Problem Loops at N0CU


94/100

2/5/2011 94

30 ferrite beads

over RG-8X cable

1 ferrite bead overmicrophone wireinside the radio

21 turns shielded cable over 1 large ferrite toro

AmplifierMic

AudioAmplifier

RFAmplifier

SPG

Station Ground

TS-930STransceiver

120VAC

Rev A

14 t 1 l f it t id

Fixes for Problem Loops at N0CU - continued


95/100

2/5/2011 95

14 turns over 1 large ferrite toroid

Amplifier

AudioAmplifier

RFAmplifier

120 VAC

240 VAC

Commercial EMI filter

SPG

Station Ground

Rev A

Choke = single inductive elementFilter = multiple L/C components

Beads and Cores


96/100

2/5/2011 96

Come in many:Sizes

ShapesMixes

Determine the useful frequency rangeCurrent and Parasitic chokes usually made of a high lossFerrite

Good for making lossy inductorsPay attention to power limitations (due to losses)

Rev A

Other Info


97/100

Adding additional grounds can INCREASEthe current surge on the house wiringin the event of a lightning strike on a nearby AC power line

Is the a problem????Bleeding off the charge techniques only increase the likelihood of a strik

Isolation:RF current chokesAC power line filters:

Linear amplifier

All other equipmentSurge Voltage Limiters (SVLs) aka Lightning ArrestorsMust be sized appropriatelyfor frequency and the RF power level usedMetal Oxide Voltage Suppressors (MOVs)

Fast risetimeLimited power dissipation capability

Gas Discharge Tubes (GDTs)Slow risetimeSignificant power dissipation capability

These devices CAN FAIL OPENafter taking a strikeHard to tell when you are no longer protected

Do not provide 100% protection against a direct strike

2/5/2011 97Rev A

Specifications for PolyPhaser IS-B50HN-C0-MA


98/100

2/5/2011 Rev A 98

Mount Type: BulkheadFrequency Range: 1.5 MHz to 400 MHz

Protected Side Connector: N FemaleSurge Side Connector: N MaleTurn On Voltage: 1200 Vdc 20 %VSWR: 1.1:1 @ 2 MHz to 400 MHzInsertion Loss: 0.1 dBRF Power: HF 3 kW

VHF 500 WUHF 250 W

ReplaceableGas Discharge

Tube (GDT)

Summary


99/100

Always use the SAFETY GroundBleed static from each antenna to Ground

Consider using a SPG (even if you dont have a Station RFGround)Regarding Lightning Grounds:

Install a multi-level protection system when possibleBest Protection is Disconnection

Antenna lines (before they enter the house)Disconnect AC power lines from equipment

Second Best Protection is DisconnectionDisconnect antenna lines from radios

Do not lay near the radioUse shorting antenna switches on the outside of the house/shack

Use an SVL at the antenna switch output and on rotator linesDisconnect AC power lines from equipment

Use extra caution regarding Bolts from the Blue100% protection is not achievable with present technologyEven a Good ground can be very expensive by Ham standards

2/5/2011 99Rev A

Summary - continued


100/100

Regarding RF Grounds:Every station has different requirements and constraints

Most stations should not need a Station RF groundIf in doubt => Where is Ground on the Space Station?Experimentation is the best way to find out what is needed

If you are not experiencing any RF related problems,continue

with what you have until a problem arisesA fix may only work for awhile, then come back, or a new

problem may emerge

Keep in mind: interference with consumer electronics maynot

be something you can fix at your station

station grounding final reva

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