Posts

Showing posts from May, 2014

Azden AZ-61 6m FM HT - Tip #2 - disabling "the beep"

Image
This post is in a series regarding the 1990's vintage Azden AZ-61 6m FM HT.


So you have dusted off  your Azden AZ-61 6m FM HT and powered it back to life.  Congratulations for giving this neat old radio a go!  One of the things you may have noticed when pressing buttons is an annoying, "beep" after each key press.  The good news is that the beep noise can be toggled off and on easily (if you know the trick).
How to toggle off and on the key press beep Step 1) Press and hold the "FUN" key while powering the radio on.


Yes, it is that simple.

Good DX and 73, NJ2X



Other related articles on NJ2X.COM:
Azden AZ-61 6m FM HT - Tip #1 - How to program the radio
Azden AZ-61 6m FM HT - Tip #2 - disabling "the beep"
Azden AZ-61 6m FM HT - Tip #3 - 1993 review article
Azden AZ-61 6m FM HT - Tip #4 - rebuilding the battery pack
Azden AZ-61 6m FM HT - Tip #5 - how to reset the radio
Azden AZ-61 6m FM HT - Tip #6 - Automatic Power-Off
Azden AZ-61 6m FM HT - Tip #7 - VFO M…

FCC Technician Exam Question Of The Day (T9B07)

Image
B) Which of the following is true of PL-259 type coax connectors?

A) They are commonly used at HF frequencies

NJ2X Notes:
The PL-259 connector is the defacto standard on HF amateur radio equipment.  The type N connector is technical superior in everyway but is not commonly found on amateur radio equipment.



Space Elevator...

Image
The Space Elevator will be built about 50 years after everyone stops laughing -- Sir Arthur C. Clarke


FCC Technician Exam Question Of The Day (T9B01)

Q) Why is it important to have a low SWR in an antenna system that uses coaxial cable feedline?

A) To allow the efficient transfer of power and reduce losses


NJ2X Notes:
A perfect standing wave ratio (SWR) is 1:1.  Higher SWR is the result of an antenna and feedline that do not have matching impedances.  Any SWR greater than 1:1 indicates some of the transmitted energy is being reflected back toward the transmitter.  This reflected energy results in RF energy being radiated from the feedline as heat (an efficiency loss).  In some cases, the reflected energy can even cause damage to the transmitter. 

FCC Technician Exam Question Of The Day (T9A11)

Q) What is meant by the gain of an antenna?

A) The increase in signal strength in a specified direction when compared to a reference antenna

NJ2X Notes:
Gain is often expressed in decibels (dB).  A theoretical antenna called an isotropic radiator is sometimes used as a reference.  An isotropic radiator is a point source located in free space and radiating equally in all directions.

FCC Technician Exam Question Of The Day (T9A10)

Q) In which direction is the radiation strongest from a half-wave dipole antenna in free space?

A) Broadside to the antenna

NJ2X Notes:
The strongest radiation from a half-wave dipole is at right angles to the antenna wire. For example, if the dipole wires are oriented so they run to the East and West then the antenna would radiate the strongest to the North and South.

FCC Technician Exam Question Of The Day (T8B05)

Q) What is a satellite beacon?

A) A transmission from a space station that contains information about a satellite

NJ2X Notes:
Satellite beacon frequencies


Beacon. An amateur station transmitting communications for the purposes of observation of propagation and reception or other related experimental activities.

FCC Technician Exam Question Of The Day (T8A02)

Q) What type of modulation is most commonly used for VHF packet radio transmissions?

A) FM


NJ2X Notes:
FM stands for Frequency Modulation.  FM is used extensively in VHF and UHF communications.

Camelopardalids Meteor Shower

Take a gander at the Camelopardalids meteor shower tonight.

Good DX and 73, NJ2X

FCC Technician Exam Question Of The Day (T9A09)

Q) What is the approximate length, in inches, of a 6 meter 1/2-wavelength wire dipole antenna?

A) 112


NJ2X Notes:
The easiest way to handle this question is to memorize the answer.

Azden AZ-61 6m FM HT - Tip #1 - How to program the radio

Image
The Azden AZ-61 6m handi-talkie (HT) can be found from time-to-time at hamfests for a relatively low price.  Buying one without the manual; however, can be a rather frustrating experience since the radio's design is far from intuitive.  This isn't the kind of radio that you can put in your hand and program without looking at a manual.  Almost anyone who has owned one would agree that it is downright difficult to program the AZ-61 (even with the original manual).

After searching the Internet, we discovered that there are rather few resources to guide the manual-less Azden AZ-61 owner in programming the radio.  As a consequence, there are probably more than a few fully functional units out there just sitting on a shelf collecting dust for lack of ability to program.  If you are one of those owners, we prepared this short tutorial on programming the Azden AZ-61 for you.  We hope it inspires you to dust-off your Azden AZ-61 (or snap one up at a hamfest), program a repeater or two,…

FCC Technician Exam Question Of The Day (T9A08)

Q) What is the approximate length, in inches, of a quarter-wavelength vertical antenna for 146 MHz?

A) 19

NJ2X Notes:
Electromagnetic waves travel at the speed of light which is 299,792,458 meters per second or for the ease of calculation we can round up to 300,000,000 m/s.  Frequency and wavelength are related and can be determined by the formulas:

Frequency = Speed of Light / Wavelength

or

Wavelength = Speed of Light / Frequency


The easiest way to deal with this question is to simply memorize the answer.

FCC Technician Exam Question Of The Day (T9A07)

Q) What is a good reason not to use a "rubber duck" antenna inside your car?

A) Signals can be significantly weaker than when it is outside of the vehicle

NJ2X Notes:
Using an antenna on the exterior of the vehicle will dramatically improve both reception and your transmitted signal.  Better to have all that RF outside the vehicle too.

Intelligence...

If the presence of electricity can be made visible in any part of the circuit, I see no reason why intelligence may not be transmitted instantaneously by electricity. -- Samuel Morse

FCC Technician Exam Question Of The Day (T9A05)

Q) How would you change a dipole antenna to make it resonant on a higher frequency?

A) Shorten it


NJ2X Notes:
The key to successfully answering this question is to remember that wavelength gets smaller as the frequency increases.  The physical dimensions of antenna correspond to the wavelength.  So to optimize an antenna for a higher frequency you need to shorten the antenna's size (and wavelength).

The old carpenter's adage, "measure twice, cut-once" doesn't quite work when shortening an antenna for a particular frequency.  That is because antennas are complex and cutting them exactly to spec or formula does not assure an antenna will behave at the desired frequency.  A more appropriate adage might be, "measure the length twice, trim a little, measure the resonance and SWR, repeat as necessary".

FCC Technician Exam Question Of The Day (T9A04)

Image
Q) What is a disadvantage of the "rubber duck" antenna supplied with most handheld radio transceivers?

A) It does not transmit or receive as effectively as a full-sized antenna

NJ2X Notes:
Many hams upgrade their HT's rubber duck with a higher performance antenna.  The trade off is typically size for performance.  However, there are times when a full size antenna is needed to make the contact.  For example, Arrow have handheld 2m/440 Mhz Yagi's that work great with an HT and can be used for satellite communication.

FCC Technician Exam Question Of The Day (T8B07)

Image
Q) With regard to satellite communications, what is Doppler shift?

A) An observed change in signal frequency caused by relative motion between the satellite and the earth station

NJ2X Notes:
The Doppler shift, named after the Austrian mathematician and physicist Christian Doppler, who proposed it in 1842, is the change in frequency for an observer moving relative to its source.  With respect to sound waves, it is commonly heard when a vehicle sounding a siren or horn approaches (rising pitch), passes (neutral), and recedes (falling pitch) from an observer.  A fast moving train blasting its horn while passing a stationary observer at a crossing is one of the more dramatic examples.



Doppler shift also occurs in radio communications with satellites.  When this happens the receives signal frequency appears to change (though the transmitted frequency remains constant).  The change is due to the satellite's high speed of motion relative to the ground station.



FCC Technician Exam Question Of The Day (T7D10)

Q) What is probably happening when an ohmmeter, connected across a circuit, initially indicates a low resistance and then shows increasing resistance with time?

A) The circuit contains a large capacitor

NJ2X Notes:
When a voltage is connected to a resistor and capacitor in series, the initial current is high as the battery transports charge from one plate of the capacitor to the other. The charging current approaches zero through time as the capacitor becomes charged.  Charging the capacitor stores energy.



FCC Technician Exam Question Of The Day (T8B11)

Q) What is a commonly used method of sending signals to and from a digital satellite?

A) FM Packet


NJ2X Notes:
FM Packet

Packet radio is a digital mode of Amateur Radio communications which is similar to computer telecommunications employing modems. The telephone modem is replaced by a "magic" box called a TNC (terminal node controller) while the telephone system is replaced by amateur radio transceivers and amateur radio waves.   Packet radio transmits a stream of data from a computer via radio to another amateur radio station.  FM packet radio transmits using frequency modulation.

FCC Technician Exam Question Of The Day (T9A03)

Q) Which of the following describes a simple dipole mounted so the conductor is parallel to the Earth's surface?

A) A horizontally polarized antenna


NJ2X Notes:
Horizontal polarization is typically used communicating in HF using.  The simple dipole is the most popular is most easily mounted so the conductors are parallel to the Earth.  Vertical polarization is typically used in VHF and UHF communication applications.

Newton of electricity...

Ampere was the Newton of electricity. -- James C. Maxwell

FCC Technician Exam Question Of The Day (T9B02)

Q) What is the impedance of the most commonly used coaxial cable in typical amateur radio installations?

A) 50 ohms

NJ2X Notes:
50 ohm coaxial cable is the defacto standard used in amateur radio applications.  It is important that all the elements in the chain have matching impedance (radio, feedline, antenna, ...).  If there is a mismatch of impedance then SWR will be affected.

FCC Technician Exam Question Of The Day (T9A06)

Q) What type of antennas are the quad, Yagi, and dish?

A) Directional antennas

NJ2X Notes:
It helpful to think visualize a directional antenna like a magnifying glass.  A directional antenna "focuses" radio energy in a particular direction.  Directional antennas include the quad, Yagi, dish, and log periodic.

FCC Technician Exam Question Of The Day (T9A02)

Image
Q) Which of the following is true regarding vertical antennas?

A) The electric field is perpendicular to the Earth

NJ2X Notes:

FCC Technician Exam Question Of The Day (T9A01)

Image
Q) What is a beam antenna?

A) An antenna that concentrates signals in one direction


NJ2X Notes:
A beam antenna is a directional antenna.  Common beam antennas include:

- Yagi
- Quad
- Log periodic

FCC Technician Exam Question Of The Day (T7C11)

Image
Q) What is a disadvantage of "air core" coaxial cable when compared to foam or solid dielectric types?

A) It requires special techniques to prevent water absorption


NJ2X Notes:
A coaxial design in which a monofilament of plastic holds the center conductor in place in a hollow plastic tube allowing the remainder of the dielectric to be air. Typical velocities of up to 84% can be achieved in this design.



FCC Technician Exam Question Of The Day (T7C04)

Q) What reading on an SWR meter indicates a perfect impedance match between the antenna and the feedline?

A) 1 to 1

NJ2X Notes:
A one-to-one, 1-to-1, or 1:1 standing wave ratio (SWR) indicates a perfect impedance match between the antenna and feedline.  It also indicates that no RF is being reflected back toward the transmitter (not a good thing).  Yes, RF does travel in both directions through coaxial cable.



FCC Technician Exam Question Of The Day (T7B11)

Q) What is a symptom of RF feedback in a transmitter or transceiver?

A) Reports of garbled, distorted, or unintelligible transmissions

NJ2X Notes:
RF feedback is caused when RF finds its way back into the shack and into the audio circuit.  Under ideal conditions, all RF is radiated from the antenna (not from the chassis or coax).  RF feedback can be a problem with end-fed antennas, poor grounding, poor match between antenna and feed line impedance, and random wire antennas.  There are several effective techniques for eliminating or reducing RF feedback including: improving your station grounding, improving your antenna counterpoise, improving the match between your feed line and antenna, and using a common-mode RF isolation choke (also known as a current balun).

I built electronics...

Image
Other kids went out and beat each other up or played baseball, and I built electronics. -- Robert Moog





FCC Technician Exam Question Of The Day (T9B09)

Q) What might cause erratic changes in SWR readings?



A) A loose connection in an antenna or a feedline



NJ2X Notes:
Loose connections can cause erratic changes in SWR.  Check your connections and secure cables mechanically.

FCC Technician Exam Question Of The Day (T7C08)

Image
Q) What instrument other than an SWR meter could you use to determine if a feedline and antenna are properly matched?



A) Directional wattmeter




NJ2X Notes:
One of the most popular directional watt meters is the Bird Watt Meter.



FCC Technician Exam Question Of The Day (T7C06)

Q) What does an SWR reading of 4:1 mean?



A) An impedance mismatch




NJ2X Notes:
Amateur radios require an impedence match of 50-ohms in the coaxial cable, antenna, or any other device connected.  A mismatch between the radio and any of the devices in the chain will cause a greater than 1:1 (perfect match) SWR.



SWR is an abreviation of standing-wave ratio.   SWR on a transmission line in an antenna system represents the the ratio of foward to reflected voltage on the line.  A perfect 1:1 ration occurs when all parts of the antenna system are matched correctly to one another.

FCC Technician Exam Question Of The Day (T7D01)

Q) Which instrument would you use to measure electric potential or electromotive force?



A) A voltmeter




NJ2X Notes:
A volt meter is a basic must-have piece of equipment for the ham.  There are very inexpensive volt meters and multi-meters available.



FCC Technician Exam Question Of The Day (T7C05)

Q) What is the approximate SWR value above which the protection circuits in most solid-state transmitters begin to reduce transmitter power?

A) 2 to 1

NJ2X Notes:
Remember, high SWR is something to be avoided.  Your equipment can be damaged while operating under high SWR conditions.  Automatic power reduction circuits are helpful; however, they do not cure the root cause.

FCC Technician Exam Question Of The Day (T8C06)

Q) For what purpose is a temporary "1 by 1" format (letter-number-letter) call sign assigned?



A) For operations in conjunction with an activity of special significance to the amateur community



NJ2X Notes:
Part 97
§97.3 Definitions.
(iii) Special event call sign system. The call sign is selected by the station licensee from a list of call signs shown on a common data base coordinated, maintained and disseminated by the amateur station special event call sign data base coordinators. The call sign must have the single letter prefix K, N or W, followed by a single numeral 0 through 9, followed by a single letter A through W or Y or Z (for example K1A). The special event call sign is substituted for the call sign shown on the station license grant while the station is transmitting. The FCC will issue public announcements detailing the procedures of the special event call sign system.

FCC Technician Exam Question Of The Day (T7C02)

Image
Q) Which of the following instruments can be used to determine if an antenna is resonant at the desired operating frequency?



A) An antenna analyzer



NJ2X Notes:
An antenna analyzer is an extremely useful device for amateur radio. We use the MFJ-269 - HF/VHF/UHF SWR ANALYZER, COUNTER.  We have used it to identifying problems with our coaxial cables as well as designing and building antennas.  There are all kinds of interesting things you can do with it beyond these basic uses.

Madness....

Image
Though this be madness, yet there is method in't. -- Hamlet, Act 2, scene 2, William Shakespeare


FCC Technician Exam Question Of The Day (T7D09)

Q) What is the characteristic appearance of a "cold" solder joint?



A) A grainy or dull surface



NJ2X Notes:
When soldering, failure to properly flux and bring the leads to melting temperature of the solder can result will be an unreliable "cold solder joint".

Checkout our soldering related articles on NJ2X.com.