FCC Commercial Element 7 pool, section 100

Subelement J

MF-HF Equip. and Comms:

Section 100

MF-HF Equipment Faults and Testing

100J1

Which of the following conditions would be a symptom of malfunction in a 2182 kHz radiotelephone system which must be reported to the Master?

A.
Much lower noise level observed during daytime operation.
Correct Answer
B.
No indication of power output when speaking into the microphone.
C.
When testing a radiotelephone alarm on 2182 kHz into an artificial antenna, the Distress frequency watch receiver becomes unmuted, an improper testing procedure.
D.
Failure to contact a shore station 600 nautical miles distant during daytime operation.

100J1

When no one speaks, then the carrier wave (made by special module in the transmitter) has nothing to module (creating radio waves), so there is nothing to broadcast, and thus no power output is indicated.

Last edited by markadlerdallas. Register to edit

Tags: none

100J2

Which would indicate a malfunction in a 2182 kHz radiotelephone system?

A.
No discernable traffic has been heard on the 2182 kHz during the radiotelephone silent periods.
B.
Dramatic increase in noise level observed during night and early morning hours.
Correct Answer
C.
Failure to contact another station 60 miles distant during daytime operation.
D.
The visual indication of power to the antenna fluctuates while testing the radiotelephone alarm signal generator into an artificial antenna.

100J2

The distress frequency 2182 kHz has a range of 50 to 100 nautical miles during day, and approximately 150 to 300 nautical miles at night, when E and D atmospheric layers do not exist.

Atmospheric conditions may affect estimated ranges.

For more info on 2182 kHz, please see Wikipedia article 2182 kHz

Last edited by markadlerdallas. Register to edit

Tags: none

100J3

Which would indicate proper operation of a SSB transmitter rated at 60 Watt PEP output in J3E mode?

A.
In SITOR (NBDP) communications, the power meter can be seen fluctuating regularly from zero to the 60 watt relative output reading.
B.
In SSB (J3E) mode, speaking into the microphone causes the power meter to fluctuate well above the 60 watt reading.
C.
A steady indication of transmitted energy on an RF power meter with no fluctuations when speaking into the microphone.
Correct Answer
D.
In SSB (J3E) voice mode, with the transmitter keyed but without speaking into the microphone, no power output is indicated.

100J3

J3E is a HF SSB radio frequency. Normally, you have the carrier, and Upper Side and the mirror Lower Side.
But SSB eliminates the carrier (the frequency which voice modulates to produce USB and LSB), and also eliminates the Lower Side Band. So, you are left with only USB, called Single Side Band.

Because all you have is a SSB, then the all the radion power goes to it, and it broadcasts further.

When no one speaks, then the carrier wave (made by special module in the transmitter) has nothing to module (creating LSB and USB), so the Upper Side Band, called the SSB has nothing to broadcast, and thus no power output is indicated.

Last edited by markadlerdallas. Register to edit

Tags: none

100J4

Which would be an indication of proper operation of a SSB transmitter rated at 60 watt PEP output?

Correct Answer
A.
In SITOR (NBDP) communications, the power meter can be seen fluctuating regularly from zero to the 60 watt relative output reading.
B.
In SSB (J3E) voice mode, with the transmitter keyed but without speaking into the microphone, power output is indicated.
C.
In SSB (J3E) mode, speaking into the microphone causes power meter to fluctuate slightly around the 60 watt reading.
D.
A steady indication of transmitted energy on an RF Power meter with no fluctuations when speaking into the microphone.

100J4

FCC defined the uses for various radio frequency ranges. It is important NOT to cross boundaries of frequencies or output power.

When power fluctuates from 0 to 60, and NOT over, then it works properly.

Last edited by markadlerdallas. Register to edit

Tags: none

100J5

Your antenna coupler/tuner becomes totally inoperative. What would you do to obtain operation on 2 HF bands?

A.
Without an operating antenna coupler/tuner, transmission is impossible.
B.
It is impossible to obtain operation on 2 different HF bands, without an operating antenna coupler/tuner.
C.
Bypass the antenna coupler/tuner and shorten the whip to 15 ft.
Correct Answer
D.
Bypass the antenna coupler/tuner. Use a straight whip or wire antenna approximately 30 ft long.

100J5

HF.. 3,000 kHz - 30,000 kHz or 3 MHz - 30 MHz

If the antenna tuner is inoperable, it won't match impedance (in Ohms) between transmitter and the antenna, causing reflected power back to the transmitter, or other malfunctions.

In salt water environment, the whip antenna, or vertical polarization is better is the waves bounce well off the water. But horizontal wire may also work, though not as well.

Antennas may be in 1/4, 1/2, 5/8, 3/4, or full wavelengths.

ASSUMING HF frequencies of 22 MHz and 8 MHz
The 22MHz has a wavelength of approximately 13.6 meters and 8 MHz is approximately 37.5 meters. Radio waves travel close to speed of light, so 300,000 km per second/8,000 kHz, or 300/8=37.5 meters. 300/22=13.6 meters.

Since the answer is in feet, meters have to be converted to feet, and then the right fraction applied.

An antenna of 30 ft is about 1/4 wave on 8 MHz and 3/4 waves on 22 MHz.

For 8 MHz, the 37.5 meters is about 123 feet, so 1/4 is about 30 feet.

For 22 MHz, the 13.6 meters is about 44.6 feet, so 3/4 is about 30 feet.

This 30 feet is the common length for both frequencies.

Last edited by markadlerdallas. Register to edit

Tags: none

100J6

Your MF-HF whip antenna breaks off and is carried away in a storm. What would you do to regain operation on MF-HF frequencies?

Correct Answer
A.
Rig a wire antenna approximately 35-40 ft long per the equipment instruction manual.
B.
Rig a wire antenna 10-15 ft long from the antenna coupler/tuner to the highest vertical support.
C.
Rig a horizontal, center-fed dipole antenna 40 ft long.
D.
Rig a long wire antenna at least 200 ft long.

100J6

MF ... 300 kHz - 3,000 kHz or 0.3 MHz - 3 MHz
HF.. 3,000 kHz - 30,000 kHz or 3 MHz - 30 MHz

35 feet is about 11 meters
40 feet is about 12 meters

300 (speed of light) / 25 MHz = 12 meters
300 (speed of light) / 27 MHz = 11 meters

Speed of light is 300,000 meters per second, but it is trimmed to 300 for the MHz calculation.

Both, 25 and 27 MHz are within the MF/HF range.

Last edited by markadlerdallas. Register to edit

Tags: none

Log in

- or -

- or -