1. Technician Licensing Class
Feed Me with Some Good Coax!
Section 19
Valid July 1, 2014
Through
June 30, 2018 1

2. Feed Me with Some Good Coax!
T7C12 A common use of coaxial cable is to carry RF signals between a radio and antenna.
T9B03 Coaxial cable is used more often than any other feedline for amateur radio antenna systems because it is easy to use and requires few special installation considerations.
T9B ohms is the impedance of the most commonly used coaxial cable in typical amateur radio installations.
Copper Wire
Outside Insulation
Mesh
Insulation

3. Feed Me with Some Good Coax!
T9B05 As the frequency of a signal passing through coaxial cable is increased the loss increases.
The Higher the frequency the more the loss
T9B07 PL-259 type coax connectors are commonly used at HF frequencies.
T9B06 A Type N connector is most suitable for frequencies above 400 MHz.
BNC, Type N, and PL 259 Connectors

4. Feed Me with Some Good Coax!
N Male
N Female
Male VHF PL-259
Male BNC
Male SMA
Female SMA
Female BNC
Female SO-239
Understand the type of connector on your radio
You may need an adapter from your coax connector to your radio
Never buy cheap coax, connectors, or adapters

5. Feed Me with Some Good Coax!
T7C11 A disadvantage of "air core" coaxial cable, when compared to foam or solid dielectric types is that it requires special techniques to prevent water absorption.
Air core
Foam core
Large coax, with hollow center - a low loss conductor. Air-insulated hard line types of feedline have the lowest loss at VHF and UHF frequencies T9B11
Smaller Heliax
solid core

6. Feed Me with Some Good Coax!
T7C09 The most common cause for failure of coaxial cables is moisture contamination.
Regular BNC, Type N, and PL259 connectors are not water-tight.
T9B08 Coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feedline loss.
T7C10 The outer jacket of coaxial cable should be resistant to ultraviolet light because UV light can damage the jacket and allow water to enter the cable.
T9B10 Electrical differences exists between the smaller RG-58 and larger RG-8 coaxial cables in that RG-8 cable has less loss at a given frequency.

7. Feed Me with Some Good Coax!
T7C02 An antenna analyzer can be used to determine if an antenna is resonant at the desired operating frequency.
T7C03 In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line.
T9B01 It is important to have a low SWR in an
antenna system that uses coaxial cable
feedline to provide efficient transfer of
power and reduce losses.
MFJ-269 SWR Analyzer
Impedance Mismatch Causes Reflected Wave

8. Feed Me with Some Good Coax!
T7C04 A “1 to 1” reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline.
SWR Reading Antenna Condition
1: Perfectly Matched
1.5: Good Match
2: Fair Match
3: Poor Match
4: Something Definitely Wrong
Coax Cable Type, Size, and Loss per 100 feet
Coax Type Size 100 MHz 400 MHz
RG-58 Small dB dB
RG-8X Medium dB dB
RG-8U Large dB dB
RG Large dB dB
Hardline Large, Rigid dB dB
A battery operated SWR analyzer for tower antenna work

9. Feed Me With Some Good Coax!9

10. Feed Me with Some Good Coax!
T7C05 2 to 1 is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power.
T7C06 An SWR reading of 4:1 means there is an impedance mismatch.
T4A05 An in-line SWR meter is connected in series with the feed line, between the transmitter and antenna, to monitor the standing wave ratio of the station antenna system.

11. Feed Me with Some Good Coax!
T9B09 A loose connection in an antenna or a feedline might
cause erratic changes in SWR readings.
Make sure all coax connections are tight to help minimize interference

12. Feed Me with Some Good Coax!
T7C08 Other than an SWR meter you could use a directional wattmeter to determine if a feedline and antenna are properly matched.
Dual/Twin Needle
Single Needle

13. Feed Me with Some Good Coax!
T7C07 Power lost in a feedline is converted into heat.
T9B04 An antenna tuner matches the antenna system impedance to the transceiver's output impedance.
Miracle QPak 50 Watt Manual Tuner
Palstar 1500 Watt Auto-Tuner
Icom 7000 with LDG 7000 Auto-Tuner
MFJ-994B 1500 Watt Auto-Tuner

14. Feed Me with Some Good Coax!
T7C01 The primary purpose of a dummy load is to prevent the radiation of signals when making tests.
Prevents signals from being sent out over the air
T7C13 A dummy load consists of a non-inductive resistor and a heat sink .
300 Watt Dry Dummy Load
Dummy Load-Can 1kw with oil
Dry Dummy Load

15. Take Aways 15

16. Take Aways
A common use of coaxial cable is to carry RF signals between a radio and antenna.
The impedance of the most commonly used coaxial cable in typical amateur radio installations is 50 ohms.
Coaxial cable is used more often than any other feedline for amateur radio antenna systems because it is easy to use and requires few special installation considerations.
Generally, the loss increases as the frequency of a signal passing through coaxial cable is increased.

17. Take Aways
The PL-259 type coax connectors are commonly used at HF frequencies.
A Type N connector is most suitable for frequencies above 400 MHz.
A disadvantage of "air core" coaxial cable when compared to foam or solid dielectric types is that it requires special techniques to prevent water absorption.
The most common cause for failure of coaxial cables is moisture contamination.

18. Take Aways
Coax connectors exposed to the weather should be sealed against water intrusion to prevent an increase in feedline loss.
The outer jacket of coaxial cable should be resistant to ultraviolet light because ultraviolet light can damage the jacket and allow water to enter the cable.
The primary electrical difference between the smaller RG-58 and larger RG-8 coaxial cables is that RG-8 cable has less loss at a given frequency.
Air-insulated hard line types of feedline have the lowest loss at VHF and UHF.

19. Take Aways
An antenna analyzer can be used to determine if an antenna is resonant at the desired operating frequency.
In general terms, standing wave ratio (SWR) is a measure of how well a load is matched to a transmission line.
It is important to have a low SWR in an antenna system that uses coaxial cable feedline to allow the efficient transfer of power and reduce losses.
A reading of 1 to 1 on an SWR meter indicates a perfect impedance match between the antenna and the feedline.

20. Take Aways
The approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power is
2 to 1.
An SWR reading of 4:1 means there is an impedance mismatch.
A loose connection in an antenna or a feedline might cause erratic changes in SWR readings.
An instrument, other than an SWR meter, that you could use to determine if a feedline and antenna are properly matched is a directional wattmeter.

21. Take Aways
An in-line SWR meter is connected in series with the feed line, between the transmitter and antenna, to monitor the standing wave ratio of the station antenna system
Power lost in a feedline is converted into heat.
An antenna tuner matches the antenna system impedance to the transceiver's output impedance.
The primary purpose of a dummy load is to prevent the radiation of signals when making tests
A dummy load consists of a non-inductive resistor and a heat sink .

22. Element 2 Technician Class Question Pool Feed Me with Some Good Coax!
Valid July 1, 2014
Through
June 30, 2018

23. T7C12 Which of the following is a common use of coaxial cable?
Carrying dc power from a vehicle battery to a mobile radio
Carrying RF signals between a radio and antenna
Securing masts, tubing, and other cylindrical objects on towers
Connecting data signals from a TNC to a computer

24. T9B03. Why is coaxial cable used more often than any
T9B03 Why is coaxial cable used more often than any other feedline for amateur radio antenna systems?
It is easy to use and requires few special installation considerations
It has less loss than any other type of feedline
It can handle more power than any other type of feedline
It is less expensive than any other types of feedline

25. T9B02. What is the impedance of the most commonly
T9B02 What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?
8 ohms
50 ohms
600 ohms
12 ohms

26. T9B05. What generally happens as the frequency of a
T9B05 What generally happens as the frequency of a signal passing through coaxial cable is increased?
The apparent SWR increases
The reflected power increases
The characteristic impedance increases
The loss increases

27. T9B07 Which of the following is true of PL-259 type coax connectors?
They are preferred for microwave operation
They are water tight
The are commonly used at HF frequencies
They are a bayonet type connector

28. T9B06. Which of the following connectors is most
T9B06 Which of the following connectors is most suitable for frequencies above 400 MHz?
A UHF (PL-259/SO-239) connector
A Type N connector
An RS-213 connector
A DB-25 connector

29. T7C11. What is a disadvantage of air core coaxial cable
T7C11 What is a disadvantage of air core coaxial cable when compared to foam or solid dielectric types?
It has more loss per foot
It cannot be used for VHF or UHF antennas
It requires special techniques to prevent water absorption
It cannot be used at below freezing temperatures

30. T7C09. Which of the following is the most common
T7C09 Which of the following is the most common cause for failure of coaxial cables?
Moisture contamination
Gamma rays
The velocity factor exceeds 1.0
Overloading

31. T9B08. Why should coax connectors exposed to the
T9B08 Why should coax connectors exposed to the weather be sealed against water intrusion?
To prevent an increase in feedline loss
To prevent interference to telephones
To keep the jacket from becoming loose
All of these choices are correct

32. T7C10. Why should the outer jacket of coaxial cable be
T7C10 Why should the outer jacket of coaxial cable be resistant to ultraviolet light?
Ultraviolet resistant jackets prevent harmonic radiation
Ultraviolet light can increase losses in the cable’s jacket
Ultraviolet and RF signals can mix together, causing interference
Ultraviolet light can damage the jacket and allow water to enter the cable

33. T9B10. What electrical difference exists between the
T9B10 What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?
There is no significant difference between the two types
RG-58 cable has less loss at a given frequency
RG-8 cable has less loss at a given frequency
RG-58 cable can handle higher power levels

34. T9B11. Which of the following types of feedline has the
T9B11 Which of the following types of feedline has the lowest loss at VHF and UHF?
50-ohm flexible coax
Multi-conductor unbalanced cable
Air-insulated hard line
75-ohm flexible coax

35. T7C02. Which of the following instruments can be used
T7C02 Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?
A VTVM
An antenna analyzer
A “Q” meter
A frequency counter

36. T7C03 What, in general terms, is standing wave ratio (SWR)?
A measure of how well a load is matched to a transmission line
The ratio of high to low impedance in a feedline
The transmitter efficiency ratio
An indication of the quality of your station’s ground connection

37. T4A05. Where should an in-line SWR meter be connected
T4A05 Where should an in-line SWR meter be connected to monitor the standing wave ratio of the station antenna system?
In series with the feed line, between the transmitter and antenna
In series with the station’s ground
In parallel with the push-to-talk line and the antenna
In series with the power supply cable, as close as possible to the radio

38. T9B01. Why is it important to have a low SWR in an
T9B01 Why is it important to have a low SWR in an antenna system that uses coaxial cable feed line?
To reduce television interference
To allow the efficient transfer of power and reduce losses
To prolong antenna life
All of these choices are correct

39. T7C04. What reading on an SWR meter indicates a
T7C04 What reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline?
2 to 1
1 to 3
1 to 1
10 to 1

40. T7C05. What is the approximate SWR value above which the
T7C05 What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?
2 to 1
1 to 2
6 to 1
10 to 1

41. T7C06 What does an SWR reading of 4:1 mean?
An antenna loss of 4 dB
A good impedance match
An antenna gain of 4
An impedance mismatch

42. T9B09 What might cause erratic changes in SWR readings?
The transmitter is being modulated
A loose connection in an antenna or a feedline
The transmitter is being over-modulated
Interference from other stations is distorting your signal

43. T7C08. What instrument other than an SWR meter could
T7C08 What instrument other than an SWR meter could you use to determine if a feedline and antenna are properly matched?
Voltmeter
Ohmmeter
Iambic pentameter
Directional wattmeter

44. T7C07 What happens to power lost in a feedline?
It increases the SWR
It comes back into your transmitter and could cause damage
It is converted into heat
It can cause distortion of your signal

45. T9B04 What does an antenna tuner do?
It matches the antenna system impedance to the transceiver's output impedance
It helps a receiver automatically tune in weak stations
It allows an antenna to be used on both transmit and receive
It automatically selects the proper antenna for the frequency band being used

46. T7C01 What is the primary purpose of a dummy load?
To prevent the radiation of signals when making tests
To prevent over-modulation of your transmitter
To improve the radiation from your antenna
To improve the signal to noise ratio of your receiver

47. T7C13 What does a dummy load consist of ?
A high-gain amplifier and a TR switch
A non-inductive resistor and a heat sink
A low voltage power supply and a DC relay
A 50 ohm reactance used to terminate a transmission line