MULTIMEDIA

The wireless Web is an exciting new development, but it is not the only one.
For many people, multimedia is the holy grail of networking. When the word is
mentioned, both the propeller heads and the suits begin salivating as if on cue.
The former see immense technical challenges in providing (interactive) video on
demand to every home. The latter see equally immense profits in it. Since multimedia
requires high bandwidth, getting it to work over fixed connections is hard
enough. Even VHS-quality video over wireless is a few years away, so our treatment
will focus on wired systems.
Literally, multimedia is just two or more media. If the publisher of this book
wanted to join the current hype about multimedia, it could advertise the book as
using multimedia technology. After all, it contains two media: text and graphics
(the figures). Nevertheless, when most people refer to multimedia, they generally
mean the combination of two or more continuous media, that is, media that have
to be played during some well-defined time interval, usually with some user interaction.
In practice, the two media are normally audio and video, that is, sound
plus moving pictures.
However, many people often refer to pure audio, such as Internet telephony or
Internet radio as multimedia as well, which it is clearly not. Actually, a better
term is streaming media, but we will follow the herd and consider real-time
audio to be multimedia as well. In the following sections we will examine how
computers process audio and video, how they are compressed, and some network
applications of these technologies. For a comprehensive (three volume) treatment
on networked multimedia, see (Steinmetz and Nahrstedt, 2002; Steinmetz and
Nahrstedt, 2003a; and Steinmetz and Nahrstedt, 2003b).

OSCILLATORS

THIS OSCILLATORS TUTORIALS SITE
This section devoted to oscillators is one of the most interesting for newcomers. You need a thorough grasp of oscillators to fully understand the later and much more complicated electronics tutorials on radio receivers and transmitters.
OSCILLATOR BASICS
Here we explain a lot of the basics involved. We discuss the principles of oscillator operation, briefly look at two popular types, Hartley Oscillators and Colpitts Oscillators as well as Frequency or Phase Stability of an oscillator. Then we go on and consider reducing Phase Noise in oscillators, discuss the effects of ambient changes on stability in oscillators and finally minimizing frequency drift in oscillators.
CLAPP OSCILLATORS
A clapp oscillator is in effect a series tuned version of the colpitts oscillator. Perhaps the simplest Colpitts oscillator to construct and get running is the "series tuned" version, more often referred to as the "Clapp Oscillator". Because there is no load on the inductor a high "Q" circuit results with a high L/C ratio and of course much less circulating current. This aids drift reduction. Because larger inductances are required, stray inductances do not have as much impact as perhaps in other circuits.
COLPITTS OSCILLATORS
Colpitts oscillators are somewhat similar to the shunt fed Hartley circuit except the Colpitts oscillator, instead of having a tapped inductor, utilises two series capacitors in its LC circuit. With the Colpitts oscillator the connection between these two capacitors is used as the centre tap for the circuit.
CRYSTAL OSCILLATORS AND CRYSTAL GRINDING
Crystal oscillators are oscillators where the primary frequency determining element is a quartz crystal. Because of the inherent characteristics of the quartz crystal the crystal oscillator may be held to extreme accuracy of frequency stability. Temperature compensation may be applied to crystal oscillators to improve thermal stability of the crystal oscillator.
What is crystal grinding? There was an exchange of emails asking about crystal grinding on the 'Flying Pigs' list. Karl Kanalz, W8TIF gave his insight and experience on the topic of crystal grinding FT-243 crystal blanks and has graciously consented to it being reprinted here.
HARTLEY OSCILLATORS
Hartley oscillator are inductively coupled, variable frequency oscillators where the oscillator may be series or shunt fed. Hartley oscillators have the advantage of having one centre tapped inductor and one tuning capacitor. This arrangement simplifies the construction of a Hartley oscillator circuit.
VOLTAGE CONTROLLED OSCILLATORS
A voltage controlled oscillator or as more commonly known, a vco, is an oscillator where the principal variable or tuning element is a varactor diode. The voltage controlled oscillator is tuned across its band by a "clean" dc voltage applied to the varactor diode to vary the net capacitance applied to the tuned circuit.
OSCILLATOR DRIFT AND DRIFT CORRECTION CIRCUITS
Oscillator drift can be related directly to frequency stability. Drift is the unwanted and unwarrented change in frequency measured over seconds, minutes or hours. Just how stable should an oscillator be? Your oscillator or any electronic project should be as state-of-the-art as is possible, consistent with your design goals.
An oscillator drift correction circuit is any circuit which automatically brings an oscillator back onto it's assigned or tuned frequency. Such circuits might be frequency synthesisers with phase locked loops, automatic fine tuning circuitry AFT or, AFC in AM Receivers and automatic temperature compensation built into an oscillator circuit.

AMATEUR RADIO

What electronics tutorials on line help is available to become a licensed Amateur Radio Operator?
This site offers some very useful and particularly comprehensive electronics tutorials to help you on your way toward becoming an amateur radio operator. Please feel free to fully explore our site.
Of course many of these electronics tutorials are applicable to experienced constructors as well as advanced electronics students looking for electronics tutorials.
Many other sites also cater for people seeking to become amateur radio operators and conduct electronics tutorials.
Just what is Amateur Radio?
The amateur radio fraternity comprises hundreds of thousands of people world wide who share a very broad common interest. Amateur radio operators come from very diverse backgrounds and age groups. Ranging from adolescents to senior citizens, boys and girls, men and women - amateur radio operators include doctors, bus drivers, vetinary surgeons, painters, engineers, homemakers, university professors, students, politicians, labourers, lawyers and the retired as well as the unemployed, there are no limits to backgrounds.
Somewhere in this wide world there are people with similar interests and backgrounds to yourself who also just happen to be amateur radio operators.
Amateur radio operators are entitled to communicate with one another world wide in accordance with the level of licensing the amateur radio operator has achieved.
What does Amateur Radio Operating entitle me to?
Depending upon your level of licensing for your particular country you might communicate by television, digital communication in conjunction with your computer, by satellite, by traditional high or very high frequency communication using FM, single sideband or more demanding, by morse code. The choice is yours. It depends on your area of interest as an amateur radio operator.
What do I need to do to become a licensed Amateur Radio Operator?
Find out the licensing requirements for amateur radio operators at your location, in particular establish the provisions for sitting for examinations to become an amateur radio operator. Next find out if there are any amateur radio clubs in your locality - the amateur radio operators at these clubs will offer you no end of help provided you approach them in a sensible way. All amateur radio operators remember when they first needed the same help you are now asking for but, remember self help comes first.
Demonstate to your new amateur radio operator friends that you are prepared to put in a bit of work on your own behalf and mainly you need advice, tuition and guidance to pass your exams. Above all else be polite.
Good amateur radio operators are always polite.
Good Luck and please do join us - you will be glad you did - it's real fun.
Ham Radio education
Anyone starting out in ham radio needs a copy of the ham radio bible. It's called "The ARRL Handbook for Radio Amateurs - 2003.
The latest is the 80th edition. It is not called the "electronics bible" for nothing. I have several editions as far back as 1943.
The mammoth 1216 pages translate theory into practice through the large variety of hands-on-projects packed into THE ARRL HANDBOOK. From Antennas to Zener diodes, Transceivers to Switching Power Supplies, HF and VHF Propagation to Power Amplifiers—it’s covered in this edition. Among the newest material is a chapter on digital signal processing, a remote-controlled automatic antenna switch and computer hardware.

OSCILLATORS

THIS OSCILLATORS TUTORIALS SITE
This section devoted to oscillators is one of the most interesting for newcomers. You need a thorough grasp of oscillators to fully understand the later and much more complicated electronics tutorials on radio receivers and transmitters.
OSCILLATOR BASICS
Here we explain a lot of the basics involved. We discuss the principles of oscillator operation, briefly look at two popular types, Hartley Oscillators and Colpitts Oscillators as well as Frequency or Phase Stability of an oscillator. Then we go on and consider reducing Phase Noise in oscillators, discuss the effects of ambient changes on stability in oscillators and finally minimizing frequency drift in oscillators.
CLAPP OSCILLATORS
A clapp oscillator is in effect a series tuned version of the colpitts oscillator. Perhaps the simplest Colpitts oscillator to construct and get running is the "series tuned" version, more often referred to as the "Clapp Oscillator". Because there is no load on the inductor a high "Q" circuit results with a high L/C ratio and of course much less circulating current. This aids drift reduction. Because larger inductances are required, stray inductances do not have as much impact as perhaps in other circuits.
COLPITTS OSCILLATORS
Colpitts oscillators are somewhat similar to the shunt fed Hartley circuit except the Colpitts oscillator, instead of having a tapped inductor, utilises two series capacitors in its LC circuit. With the Colpitts oscillator the connection between these two capacitors is used as the centre tap for the circuit.
CRYSTAL OSCILLATORS AND CRYSTAL GRINDING
Crystal oscillators are oscillators where the primary frequency determining element is a quartz crystal. Because of the inherent characteristics of the quartz crystal the crystal oscillator may be held to extreme accuracy of frequency stability. Temperature compensation may be applied to crystal oscillators to improve thermal stability of the crystal oscillator.
What is crystal grinding? There was an exchange of emails asking about crystal grinding on the 'Flying Pigs' list. Karl Kanalz, W8TIF gave his insight and experience on the topic of crystal grinding FT-243 crystal blanks and has graciously consented to it being reprinted here.
HARTLEY OSCILLATORS
Hartley oscillator are inductively coupled, variable frequency oscillators where the oscillator may be series or shunt fed. Hartley oscillators have the advantage of having one centre tapped inductor and one tuning capacitor. This arrangement simplifies the construction of a Hartley oscillator circuit.
VOLTAGE CONTROLLED OSCILLATORS
A voltage controlled oscillator or as more commonly known, a vco, is an oscillator where the principal variable or tuning element is a varactor diode. The voltage controlled oscillator is tuned across its band by a "clean" dc voltage applied to the varactor diode to vary the net capacitance applied to the tuned circuit.
OSCILLATOR DRIFT AND DRIFT CORRECTION CIRCUITS
Oscillator drift can be related directly to frequency stability. Drift is the unwanted and unwarrented change in frequency measured over seconds, minutes or hours. Just how stable should an oscillator be? Your oscillator or any electronic project should be as state-of-the-art as is possible, consistent with your design goals.
An oscillator drift correction circuit is any circuit which automatically brings an oscillator back onto it's assigned or tuned frequency. Such circuits might be frequency synthesisers with phase locked loops, automatic fine tuning circuitry AFT or, AFC in AM Receivers and automatic temperature compensation built into an oscillator circuit.

Ohm's Law Tutorial

The voltmeter is connected across the resistor, to measure the voltage across the resistor. The ammeter is connected in series with the resistor, to measure the current flowing around the circuit and through the resistor.
Mr Ohm discovered that if you double the voltage across the resistor then the current through it doubles. If you halve the voltage then the current is halved. This means that the current is PROPORTIONAL to the voltage.
He also found that if you double the value of the resistor then the current through it is halved. If the value of the resistor is halved the the current is doubled. Thus the current is INVERSELY PROPORTIONAL to the resistance.

To use the VIR triangle place your finger over the value you wish to find. If you wish to find V then multiply I by R If you wish to find I then divide V by R.

On-line games

Off the rails

play now

LC FILTERS DESIGN

THIS FILTERS TUTORIALS SITE

This chapter lc filters is the most interesting tutorial of all for newcomers to radio design. Without a thorough grasp of lc filters you will never fully understand the ramifications of receiver and transmitter design.

Here you should gain a full understanding of the selection and design basics for lc filters. These lc filters topics cover everything necessary for your continued understanding of radio design and transmitter design.

It is absolutely imperative you fully understand the basic terms capacitance, chokes, impedance, inductance, "Q", reactance, resonance and toroids to complete these very comprehensive tutorials.
LOW PASS FILTERS

We will start with low pass filters (LPF) because they are the basis of other filter designs. High pass or band pass filters are often simply transformations from low pass filter designs. It is simply two L networks added together.
HARMONIC TRAP FILTERS

With the addition of one small component, a capacitor, we can transform a low pass filter into a filter with near infinite attenuation at a designed trap frequency. I call this an "harmonic trap filter".
BAND PASS FILTERS

LC Band pass filters are usually LC filters containing resonator combinations of inductance and capacitance which are designed mathematically to respond to design frequencies while rejecting all other out of band frequencies. Because LC bandpass filters have inherent limitations these statements should not be taken too literally.
CONVENIENT FILTER SOFTWARE PROGRAM

This LC and crystal filter software was written by Neil Heckt of Almost All Digital Electronics as an aid for filter designers to simply plug in various filter parameters and hey presto! there is your finished design. I will present you with the design example of a crystal filter of the crystal ladder filters variety as designed on my evaluation copy of the downloaded software.
HIGH PASS FILTERS

Assuming you have mastered the design of low pass LC filters we will now proceed to the design of a high pass filters. A high pass filter is simply the transformation of a low pass filter. Just as one high pass filter design example, we will say we need a five pole butterworth filter with a cut off frequency Fc at 2000 Khz. That is we want to pass all frequencies above 2000 Khz but attenuate those below 2000 Khz, that is the function of a high pass filter.
IF AMPLIFIER BAND PASS FILTERS

IF amplifier filters are LC resonator stages separated by individual stages of amplification. The principle is called synchronously tuned filters stages. In IF amplifier filters there can be any number of resonators per individual stage.
ACTIVE BAND PASS FILTERS

Active bandpass filters are simply filters constructed by using operational amplifiers as active devices configured to simulate inductors or what are known as "gyrators". Active bandpass filters are used largely at audio frequencies where otherwise the size of the inductor would become prohibitive. The are many different types of active filters including high pass, low pass, band reject and there are numerous responses including multiple feedback bandpass (MFBP), dual-amplifier bandpass (DABP) and, state variable bi-quad all pole circuits. Interestingly all known filter responses such as Butterworth and Chebyshev may be synthesised.

Buy Lancaster's Active Filter Cookbook - Don Lancaster
NARROW BAND PASS FILTERS

Narrow band filters are filters where the fractional bandwidth is extremely small in a relative sense. My personal definition of a narrow band filter is where the narrow band filter has a fractional bandwidth NOT exceeding 1%. A filter with a bandwidth of 200 Khz ( ± 100 Khz ) centred around 7100 Khz would represent a bandwidth of about 2.86% Here I present a very detailed design of a Butterworth narrow band filter.
ANTENNA PRE-SELECTOR FILTERS

I'm asked every so often to produce a page on antenna pre-selector filters. An antenna pre-selector filter is nothing more than a narrow band filter, a topic already covered at some length on another page. Some confusion results because the narrow band filter topic contains no provision for variable tuning. There are several reasons for this. Contrary to your immediate impressions I find no particular benefit in introducing variable tuning to an antenna pre-selector filter. I can see a number of drawbacks however.