September 30, 2013

FCC Technician Exam Question Of The Day (T1D03)

Q) When is the transmission of codes or ciphers allowed to hide the meaning of a message transmitted by an amateur station?

A) Only when transmitting control commands to space stations or radio control craft


NJ2X Notes:
Allowing encryption or other methods of protecting control commands to a space station or radio control craft helps assure the control operator stays in control.  Physical access to an amateur radio in space is somewhat limited (i.e. you need a rocket to get there).  It is important to understand that codes or cipers are not allowed to hide the meaning of a message for other types of transmissions.

September 29, 2013

FCC Technician Exam Question Of The Day (T1D11)

Q) Which of the following types of communications are permitted in the Amateur Radio Service?

A) Brief transmissions to make station adjustments.


NJ2X Note:
Section 97.111(b) provides for one-way communications. In summary, auxiliary, beacon, space and stations in distress are specifically authorized to make certain one-way transmissions.  Additionally, an amateur station may transmit the following types of one-way communications:
  1. Brief transmissions necessary to make adjustments to the station;
  2. Brief transmissions necessary for establishing two-way communications with other stations;
  3. Telecommand;
  4. Transmissions necessary to providing emergency communications;
  5. Transmissions necessary to assisting persons learning, or improving proficiency in, the international Morse code;
  6. Transmissions necessary to disseminate an information bulletin; and
  7. Telemetry.


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September 28, 2013

FCC Technician Exam Question Of The Day (T0C04)

Q) What factors affect the RF exposure of people near an amateur station antenna?

A. Frequency and power level of the RF field
B. Distance from the antenna to a person
C. Radiation pattern of the antenna
D. All of these choices are correct

 


NJ2X Notes:
Exposure to radio frequency radiation can affect people.  Factors influencing the exposure level include frequency, power, distance, and the transmitting antenna's radiation pattern.



September 27, 2013

Quick Guide To Common Multimeter Symbols and Abbreviations

Ever wonder what all the symbols and abbreviations mean on your multimeter?  Here is NJ2X's handy quick reference guide to help you decode some of the more common symbols and abbreviations appearing on multimeters.

 Capacitor
Diode
AC Alternating current or voltage
~ Alternating current or voltage
•))) Audible Continuity
DC Direct current or voltage
Direct current or voltage
V Volts
mV Millivolts (1 x 10- 3 volts)
A Ampere (amps). Current
Fuse
Ground
mA Milliampere (1 x 10-3 amps)
uA Microampere (1 x 10-6 amps)
nS Nanosiemens (1 x 10-9 siemens). Conductance (1/W)
Ω Ohms. Resistance
Kilohm (1 x 103 ohms). Resistance
Megohm (1 x 106 ohms). Resistance
Hz Hertz (1 cycle/sec). Frequency
kHz Kilohertz (1 x 103 cycles/sec). Frequency
mF Microfarads (1 x 10-6 Farads). Capacitance
nF Nanofarads (1 x 10-9 Farads). Capacitance
- Negative
+ Positive


Good DX and 73, NJ2X


Other related articles on NJ2X.COM:
Using your multimeter: Continuity Test
What is the schematic symbol for a ferrite bead?



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© Michael W. Maher and NJ2X.COM, 2013. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Michael W. Maher and NJ2X.COM with appropriate and specific direction to the original content.

FCC Technician Exam Question Of The Day (T1D02)

Q) On which of the following occasions may an FCC-licensed amateur station exchange messages with a U.S. military station?

A) During an Armed Forces Day Communications Test

NJ2X Notes:
The annual Armed Forces Day celebration features traditional military-to-amateur crossband communications SSB voice and Morse code tests. These tests give Amateur Radio operators and shortwave listeners an opportunity to demonstrate their individual technical skills and to receive recognition from the Secretary of Defense and/or the appropriate military radio station for their proven expertise. QSL cards are provided to those stations making contact with the military stations.



September 26, 2013

FCC Technician Exam Question Of The Day (T1C10)

Q) How soon may you operate a transmitter on an amateur service frequency after you pass the examination required for your first amateur radio license?

A) As soon as your name and call sign appear in the FCC's ULS database.


NJ2X Note:
The FCC database will become one of your most frequented sites immediately after taking your test.  It is a little like being a kid on Christmas morning when your call finally appears.  Fun!

September 25, 2013

FCC Technician Exam Question Of The Day (T0C03)

Q) What is the maximum power level that an amateur radio station may use at VHF frequencies before an RF exposure evaluation is required?

A) 50 watts PEP at the antenna

NJ2X Notes:

FCC Part 97.3 Definitions

PEP (peak envelope power). The average power supplied to the antenna transmission line by a transmitter during one RF cycle at the crest of the modulation envelope taken under normal operating conditions.


September 24, 2013

FCC Technician Exam Question Of The Day (T1D01)

Q) With which countries are FCC-licensed amateur stations prohibited from exchanging communications?

A) Any country whose administration has notified the ITU that it objects to such communications



NJ2X Note:
See the FCC Part 97 - section 97.111 Authorized transmissions

Sec. 97.111 Authorized transmissions

(a) An amateur station may transmit the following types of two-way communications:
(1) Transmissions necessary to exchange messages with other stations in the amateur service, except those in any country whose administration has notified the ITU that it objects to such communications. The FCC will issue public notices of current arrangements for international communications. (2) Transmissions necessary to meet essential communication needs and to facilitate relief actions. (3) Transmissions necessary to exchange messages with a station in another FCC-regulated service while providing emergency communications; (4) Transmissions necessary to exchange messages with a United States government station, necessary to providing communications in RACES; and (5) Transmissions necessary to exchange messages with a station in a service not regulated by the FCC, but authorized by the FCC to communicate with amateur stations. An amateur station may exchange messages with a participating United States military station during an Armed Forces Day Communications Test. (b) In addition to one-way transmissions specifically authorized elsewhere in this part, an amateur station may transmit the following types of one-way communications: (1) Brief transmissions necessary to make adjustments to the station; (2) Brief transmissions necessary to establishing two-way communications with other stations; (3) Telecommand; (4) Transmissions necessary to providing emergency communications; (5) Transmissions necessary to assisting persons learning, or improving proficiency in, the international Morse code; and (6) Transmissions necessary to disseminate information bulletins. (7) Transmissions of telemetry. [54 FR 25857, June 20, 1989, as amended at 56 FR 56171, Nov. 1, 1991; 71 FR 25982, May 3, 2006; 71 FR 66462, Nov. 15, 2006]



September 23, 2013

FCC Technician Exam Question Of The Day (T1B05)

Q) Which 70 cm frequency is authorized to a Technician Class license holder operating in ITU Region 2?

A) 443.350 MHz

NJ2X Note:
Remember there is an inverse relationship between frequency and wavelength.

Wavelength (meters) = 300 / frequency (Mhz)

For this question:
  • Wavelength (meters) = 300 / 443.350 = 0.676 meters
  • A wavelength of 0.676 m (67.6 cm)  is close to the wavelength to 70 cm (or 0.700 m).


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September 22, 2013

FCC Technician Exam Question Of The Day (T1D08)

Q) When may the control operator of an amateur station receive compensation for operating the station?

A) When the communication is incidental to classroom instruction at an educational institution.

NJ2X Note:
The term "amateur" reflects the principle that Amateur Radio and its skilled operators are committed to the pursuit of their interests in radio without financial compensation.  The motivation of amateur radio operators is fundamentally different than in commercial radio which operates necessarily for profit.

September 21, 2013

FCC Technician Exam Question Of The Day (T1D10)

Q) What is the meaning of the term broadcasting in the FCC rules for the amateur services?

A) Transmissions intended for reception by the general public.


NJ2X Note:
The ARRL maintains a regular schedule of practice CW transmissions on the amateur radio bands.  These are intended for reception by amateur radio operators and not the general public.  This is a wonderful way to learn and improve your Morse code skills.



September 20, 2013

Project: New Old Stock Electronic Lock Kit

The return of cooler fall weather and rain prompted a trip to the workshop for a little solder smoke aroma therapy.  It had been a long hot summer and sadly the workshop was idle during most of it.

The first thing we decided to do was to perform a little clutter management.  All of the horizontal surfaces had become parking places for various tools and detritus.  We needed to reclaim some workspace and create a safe work environment.

During the cleanup we discovered a long-forgotten kit in a polybag.  It was a vintage electronic lock kit perhaps from the 80's that we had purchased for a couple of dollars via eBay.  The kit was rather basic having only a schematic, a bag of parts, and PCB without any markings.  No step-by-step instructions were provided.  A little mystery to add to the fun!

The purpose of the device once built is to activate a double-pole-single-throw switching relay when the user enters the correct sequence of four push buttons.  A reset button returns the relay to its normal setting.  The kit requires a 12v input.

We had a spare unused enclosure on the shelf that looked like it would fit the kit perfectly.

NJ2X Electronic Lock - Finished Build

Step 1: Review all the components and determine the target location on the PCB.
  • This went fairly well.  The only tricky part was to make sure the orientation of the transistor, capacitor, and IC's was correct.  The schematic helped.
Step 2: Solder in the jumpers.
  • Some of the jumpers needed to located underneath components.  This little insight helped us keep the build looking nice and neat.
Step 3: Solder all the components.
  • Pay careful attention to the IC's.  There were three IC's with the same number of pins though 2 different part numbers.  An easy mistake would have been to misplace the IC's.
  • We used a generous amount of flux on the parts and board due to obvious oxidization and a little corrosion.  The flux helped greatly with cleaning and promoting good soldering.
Step 4: Clean up the solder flux.
  • Using cotton swabs and alcohol quickly cleaned the PCB and components of flux residue.
  • This step keeps the build looking nice and neat.
Step 5: Mount the pushbuttons.
  • We used a drill press and 5/8 inch drill bit to prepare the faceplate.
Step 6: Solder wires for power, push buttons, and relay switching
  • We used Anderson PowerPole connectors (of course) for the 12v power input with a bit of shrink tubing for added strain relief.
  • We added three wires to the relay switch.  These can be used for switching applications.
  • We used heavier gage wire than what the kit was drilled for.  This was quickly remedied with a Dremel tool and suitable bit.
Step 7: Power up the circuit and test it
  • Test 1: Activate the relay (no load) by entering the correct lock sequence.  SUCCESS
  • Test 2: The relay is not activated (no load) by entering an incorrect lock sequence.  SUCCESS
  • Test 3: Add a load (audio continuity tester) to the switch inputs and repeat tests #1 and #2.  SUCCESS
  • Test 4: Repeat tests #3 using the other pole of the relay. SUCCESS
This old kit was a great way to kick off the kit building season.  The solder smoke aroma therapy worked as it should resulting in a sense of satisfaction having build a neat little electronic gadget.

On the application side, we still haven't decided what we need to turn on or off with this device yet.  You never know when inspiration will strike.  When it does, we will put this device to good use.


Good DX and 73, NJ2X


Other project articles on NJ2X.COM:

© Michael W. Maher and NJ2X.COM, 2013. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Michael W. Maher and NJ2X.COM with appropriate and specific direction to the original content.

FCC Technician Exam Question Of The Day (T0C02)

Q) Which of the following frequencies has the lowest Maximum Permissible Exposure limit?

A) 50 MHz

NJ2X Notes:

FCC Limits for Maximum Permissible Exposure (MPE) - from §1.1310
Frequency Range
(MHz)
Electric Field
Strength (V/m)
Magnetic Field
Strength (A/m)
Power Density
(mW/cm2)
Averaging Time
(minutes)
0.3-3.06141.63100 6
3.0-301842/f4.89/f900/f2 †6
30-30061.40.1631.06
300-1500--f/3006
1500-100,000--56





September 19, 2013

FCC Technician Exam Question Of The Day (T0C01)

Q) What type of radiation are VHF and UHF radio signals?

A) Non-ionizing radiation


NJ2X Notes:
Non-ionizing radiation refers to any type of electromagnetic radiation that does not carry enough energy to ionize atoms or molecules.  Non-ionizing radiation with sufficient power can cause heating in living tissue.  VHF and UHF radio signals are non-ionizing radiation.


Non-ionizing Radiation Warning Sign
 
Ionization removes an electron from an atom or molecule.  Ionizing radiation is dangerous since it damages DNA.  Examples of ionizing radiation include X-rays and gamma rays.

Ionizing Radiation Warning Sign

September 18, 2013

FCC Technician Exam Question Of The Day (T0B11)

Q) Which of the following establishes grounding requirements for an amateur radio tower or antenna?

A) Local electrical codes


NJ2X Notes:

September 17, 2013

FCC Technician Exam Question Of The Day (T1C11)

Q) If your license has expired and is still within the allowable grace period, may you continue to operate a transmitter on amateur service frequencies?

A) No, transmitting is not allowed until the ULS database shows that the license has been renewed.


NJ2X Note:
Even if you are not active and do not have a station, do consider renewing your amateur radio license.  The cost is low and you never know when you may have the opportunity to operate on a club station or special event station with your own call.  That way you will avoid the regret from allowing your call to lapse.

You can check on the status of your license on-line via the FCC ULS database.


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September 16, 2013

Aut Viam Invenium Aut Facium - I’ll either find a way or make one

Aut Viam Invenium Aut Facium - I’ll either find a way or make one

FCC Technician Exam Question Of The Day (T9B10)

Q) What electrical difference exists between the smaller RG-58 and larger RG-8 coaxial cables?

A) RG-8 cable has less loss at a given frequency

NJ2X Notes:
Besides electrical differences, physical handling and routing are sometimes considerations.  For example, you would not want to use a heavy and stiff coaxial cable for a short cable between an HT and a handheld antenna.

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September 15, 2013

FCC Technician Exam Question Of The Day (T0A08)

Q) What is one way to recharge a 12-volt lead-acid station battery if the commercial power is out?

A) Connect the battery to a car's battery and run the engine

NJ2X Notes:
A car has an electrical generator that is used to maintain the vehicle's battery.  This can be leveraged to also recharge a 12-volt battery for amateur radio use in an emergency.

September 14, 2013

FCC Technician Exam Question Of The Day (T0A04)

Q) What is the purpose of a fuse in an electrical circuit?

A) To interrupt power in case of overload

NJ2X Notes:
Fuses play an important role by protecting a circuit from current overload. Fundamentally a fuse is a short length of wire in a glass envelope that will melt at or above a specific current level. The basic idea is to design a circuit so that the fuse will break down before the wires and components are destroyed or catch fire. You want the fuse to be the weakest link in the electrical chain.

September 13, 2013

FCC Technician Exam Question Of The Day (T0A09)

Q) What kind of hazard is presented by a conventional 12-volt storage battery?

A) Explosive gas can collect if not properly vented

NJ2X Notes:
Hydrogen when mixed with oxygen forms an explosive gas which can be easily ignited by a spark or open flame.  Hygrogen is produced by 12-volt lead-acid batteries and can collect if not vented properly.

September 12, 2013

FCC Technician Exam Question Of The Day (T0A10)

Q) What can happen if a lead-acid storage battery is charged or discharged too quickly?

A) The battery could overheat and give off flammable gas or explode

NJ2X Notes:
It is important to treat 12-volt lead-acid batteries with respect.  They can be dangerous in spite of the apparent low voltage.  A typical car battery is capable of producing considerable current during discharge.  If charged or discharged too quickly batteries can overheat, give off hyrdogen gas, or even explode.

September 11, 2013

FCC Technician Exam Question Of The Day (T0A05)

Q) Why is it unwise to install a 20-ampere fuse in the place of a 5-ampere fuse?

A) Excessive current could cause a fire

NJ2X Notes:
It is important that the fuse be the weakest link in the electrical chain.  Electrical fire can be the penalty for using the wrong fuse.


September 10, 2013

FCC Technician Exam Question Of The Day (T0A06)

Q) What is a good way to guard against electrical shock at your station?

A. Use three-wire cords and plugs for all AC powered equipment
B. Connect all AC powered station equipment to a common safety ground
C. Use a circuit protected by a ground-fault interrupter
D. All of these choices are correct

NJ2X Notes:
Electrical safety in the shack is important.  Don't take shortcuts or become complacent with electricity.

September 9, 2013

FCC Technician Exam Question Of The Day (T0A07)

Q) Which of these precautions should be taken when installing devices for lightning protection in a coaxial cable feedline?

A) Ground all of the protectors to a common plate which is in turn connected to an external ground


September 8, 2013

FCC Technician Exam Question Of The Day (T0A03)

Q) What is connected to the green wire in a three-wire electrical AC plug?

A) Safety ground

NJ2X Notes:
The green wire in house wiring AC is designated for safety ground.

September 7, 2013

FCC Technician Exam Question Of The Day (T0A11)

Q) Which of the following is good practice when installing ground wires on a tower for lightning protection?

A) Ensure that connections are short and direct

NJ2X Notes:
Effective tower grounding is very important with many considerations.  When installing ground wires on a tower for lightning protection you need to make sure the connections are short and direct.  It is also important to avoid sharp bends in the grounding wire as these can present an impedance to lightning.

September 6, 2013

FCC Technician Exam Question Of The Day (T0A12)

Q) What kind of hazard might exist in a power supply when it is turned off and disconnected?

A) You might receive an electric shock from stored charge in large capacitors

NJ2X Notes:
Capacitors store electrical energy.  This energy can be released quickly through contact and are thus a shock hazard.
  • Avoid working on energized electrical equipment or circuits. 
  • Test capacitors with a suitable voltmeter and discharge before working on or near them.
  • Use suitable insulators during the discharge process.
  • After discharging the capacitor verify that there is no residual charge with a suitable voltmeter.

September 5, 2013

FCC Technician Exam Question Of The Day (T0A13)

Q) What safety equipment should always be included in home-built equipment that is powered from 120V AC power circuits?

A) A fuse or circuit breaker in series with the AC "hot" conductor

NJ2X Notes:
A fuse or circuit breaker protects equipment from overload and damage.

September 4, 2013

FCC Technician Exam Question Of The Day (T0B01)

Q) When should members of a tower work team wear a hard hat and safety glasses?

A) At all times when any work is being done on the tower

NJ2X Notes:
Gravity is always present, and towers involve heights.  This means there is an ever-present risk of objects falling while working on a tower.  Hard hats and safety glasses help mitigate the risk of injury.






September 3, 2013

FCC Technician Exam Question Of The Day (T0B02)

Q) What is a good precaution to observe before climbing an antenna tower?

A) Put on a climbing harness and safety glasses

NJ2X Notes:
Tower safety is essential.  Hard hats, harnesses, and safety glasses are extremely important safety gear which can save lives.


September 2, 2013

FCC Technician Exam Question Of The Day (T0A02)

Q) How does current flowing through the body cause a health hazard?

A. By heating tissue
B. It disrupts the electrical functions of cells
C. It causes involuntary muscle contractions
D. All of these choices are correct


NJ2X Notes:
Voltages as low as 30v are considered dangerous.


September 1, 2013

FCC Technician Exam Question Of The Day (T0A01)

Q) Which is a commonly accepted value for the lowest voltage that can cause a dangerous electric shock?


A) 30 volts


NJ2X Notes:
Any voltage above 30V is commonly considered to be capable of delivering dangerous electric shock.  Low voltages can still be dangerous even if they're too low to directly cause shock injury.   They may be enough to startle and cause an accident.