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Coax Cable

Lake Area Radio Klub

Spring 2012

- ELEMENT 3 SUB-ELEMENTS(Groupings)
- 1 - Your Passing CSCE
- 2 - Your New General Bands
- 3 - FCC Rules
- 4 - Be a VE
- 5 - Voice Operations
- 6 - CW Lives
- 7 - Digital Operating
- 8 - In An Emergency
- 9 - Skywave Excitement

- ELEMENT 3 SUB-ELEMENTS(Groupings)
- 10 - Your HF Transmitter
- 11 - Your Receiver
- 12 - Oscillators & Components
- 13 - Electrical Principles
- 14 - Circuits
- 15 - Good Grounds
- 16 - HF Antennas
- 17 - Coax Cable
- 18 -RF & Electrical Safety

- 50 and 75 ohms are the typical characteristic impedances of coaxial cables used for antenna feed lines at amateur stations. (G9A02)
- The attenuation of coaxial cable increases as the frequency of the signal it is carrying increases.(G9A05)
- RF feed line losses usually expressed in dB per 100 ft. (G9A06)

- The percentage of power loss that would result from a transmission line loss of 1 dB would be approx. 20.5 %. (G5B10)
- 300 ohms is the characteristic impedance of flat ribbon TV type twinlead. (G9A03)
- The distance between the centers of the conductors and the radius of the conductors determine the characteristic impedance of a parallel conductor antenna feed line. (G9A01)

300 Ohm Twin Lead

Air Dielectric Coaxial Cable

Parallel two-wire line

- To prevent standing waves on an antenna feed line, the antenna feed-point impedance must be matched to the characteristic impedance of the feed line. (G9A07)
- A difference between feed-line impedance and antenna feed-point impedance is the reason for the occurrence of reflected power at the point where a feed line connects to an antenna. (G9A04)
- Standing wave ratio can also be determined with a directional wattmeter. (G4B10)

- A standing wave ratio of 1:1 will result from the connection of a 50-ohm feed line to a non-reactive load having a 50-ohm impedance. (G9A11)

SWR = Z1 / Z2

50 / 50

1 : 1 VSWR

- If you feed a vertical antenna that has a 25-ohm feed-point impedance with 50-ohm coaxial cable, the SWR will be 2:1. (G9A12)
- A 4:1 standing wave ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 200-ohm impedance. (G9A09)
- A standing wave ratio of 5:1 will result from the connection of a 50-ohm feed line to a non-reactive load having a 10-ohm impedance. (G9A10)

SWR = Z1 / Z2

50 / 25

2:1 VSWR

SWR = Z1 / Z2

200/ 50

4:1 VSWR

50/ 10

5:1 VSWR

SWR = Z1 / Z2

- If the SWR on an antenna feed line is 5 to 1, and a matching network at the transmitter end of the feed line is adjusted to 1 to 1 SWR, the resulting SWR on the feed line is still 5 to 1. (G9A08)
- The antenna tuner allows the transmitter to see a matched impedance
- This delivers full power.
- It does not change the antenna or feedline impedance on its output.

Antenna tuner with built in dual needle SWR meter

SWR = Z1 / Z2

300/ 50

6:1 VSWR

- The type-N connector is a moisture-resistant RF connector useful to 10 GHz. (G6C16)

Type-N

Type-N

- The SMA connector is a small threaded connector suitable for signals up to several GHz. (G6C18)
- A PL-259 connector is commonly used for RF service at frequencies up to 150 MHz. (G6C13)

A high quality SMA connector is useable to 18 GHz and beyond

Male PL-259

PL-259 T-Connector

- 200 feet is the maximum height above ground to which an antenna structure may be erected without requiring notification to the FAA and registration with the FCC, provided it is not at or near a public use airport. (G1B01)

Maximum Antenna Height without FCC Approval.

200 Ft.

Coax Cable

Valid July 1, 2011

Through

June 30, 2015

25 and 30 ohms

50 and 75 ohms

80 and 100 ohms

500 and 750 ohms

It is independent of frequency

It increases

It decreases

It reaches a maximum at approximately 18 MHz

Ohms per 1000 ft

dB per 1000 ft

Ohms per 100 ft

dB per 100 ft

10.9 %

12.2 %

20.5 %

25.9 %

50 ohms

75 ohms

100 ohms

300 ohms

The distance between the centers of the conductors and the radius of the conductors

The distance between the centers of the conductors and the length of the line

The radius of the conductors and the frequency of the signal

The frequency of the signal and the length of the line

The antenna feed point must be at DC ground potential

The feedline must be cut to an odd number of electrical quarter wavelengths long

The feedline must be cut to an even number of physical half wavelengths long

The antenna feed point impedance must be matched to the characteristic impedance of the feed line

Operating an antenna at its resonant frequency

Using more transmitter power than the antenna can handle

A difference between feed line impedance and antenna feed point impedance

Feeding the antenna with unbalanced feedline

Standing Wave Ratio

Antenna front-to-back ratio

RF interference

Radio wave propagation

G9A11 What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 50-ohm impedance?

2:1

1:1

50:50

0:0

2:1

2.5:1

1.25:1

You cannot determine SWR from impedance values

G9A09 What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 200-ohm impedance?

4:1

1:4

2:1

1:2

G9A10 What standing-wave-ratio will result from the connection of a 50-ohm feed line to a non-reactive load having a 10-ohm impedance?

2:1

50:1

1:5

5:1

G9A08 If the SWR on an antenna feedline is 5 to 1, and a matching network at the transmitter end of the feedline is adjusted to 1 to 1 SWR, what is the resulting SWR on the feedline?

1 to 1

5 to 1

Between 1 to 1 and 5 to 1 depending on the characteristic impedance of the line

Between 1 to 1 and 5 to 1 depending on the reflected power at the transmitter

1.5:1

3:1

6:1

You cannot determine SWR from impedance values

A moisture-resistant RF connector useful to 10 GHz

A small bayonet connector used for data circuits

A threaded connector used for hydraulic systems

An audio connector used in surround-sound installations

A large bayonet-type connector usable at power levels in excess of 1 KW.

A small threaded connector suitable for signals up to several GHz.

A connector designed for serial multiple access signals.

A type of push-on connector intended for high-voltage applications.

Octal

RJ-11

PL-259

DB-25

G1B01 What is the maximum height above ground to which an antenna structure may be erected without requiring notification to the FAA and registration with the FCC, provided it is not at or near a public-use airport?

50 feet

100 feet

200 feet

300 feet

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