Monday, August 31, 2009

Basic electronics - transistors and semiconductors

Countdown Timer: 5 weeks 1 day to go

Right, we covered a fair bit under the banner of basic electronics, including resistors, capacitors, inductors etc. Now we need to do a wee bit on transistors. The course syllabus, as outlined in the Exam Notes and Sample Paper document from IRTS, says the following needs to be known:

- PNP- and NPN-transistor
- Amplification factor
- Field effect vs. bipolar transistor (voltage vs. current driven)
- The transistor in the:
- common emitter [source] circuit
- common base [gate] circuit
- common collector [drain] circuit
- input and output impedances of the above circuits

There was a question in Sample Paper 3 which asked the candidate to identify a diagram. I have included the question here on the right. It would be a good exercise to learn the diagrams of the four main types of transistor in case this comes up, and also to have some sort of rudimentary knowledge of what a transistor does.

Here is a brief introduction to the transistor from Wikipedia:

In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, the transistor provides amplification of a signal.

The transistor is the fundamental building block of modern electronic devices, and is used in radio, telephone, computer and other electronic systems. The transistor is often cited as being one of the greatest achievements in the 20th century, and some consider it one of the most important technological breakthroughs in human history. Some transistors are packaged individually but most are found in integrated circuits.

And a nice simple explanation from the Williamsons Labs site:

A Transistor can be thought of as a device that is active in only One Direction: It can draw more or less current through its load resistor (sometimes referred to as a pull-up resistor).

It can either Source Current or it can Sink Current, it Cannot do Both.

Types of Transistor:

Types of transistor (from this website):

There are two types of standard transistors, NPN and PNP, with different circuit symbols. The letters refer to the layers of semiconductor material used to make the transistor. Most transistors used today are NPN because this is the easiest type to make from silicon. If you are new to electronics it is best to start by learning how to use NPN transistors.

The leads are labelled base (B), collector (C) and emitter (E).

In addition to standard (bipolar junction) transistors, there are field-effect transistors which are usually referred to as FETs.

Saturday, August 29, 2009

Half way there - so let's keep going

Countdown Timer: 5 weeks 3 days to go

I decided to do the test with 11 weeks to go, so I'm now at the halfway point. It feels good to have done so much work, but there is much still to be done. For all those out there intending to sit the exam, remember you have plenty of time to go. So no panic, just yet!

Those of you who haven't seen the new IRTS Sample Paper should give it a go (and remember, don't cheat - no Googling!)

Some things that I must cover in the next few days would include semiconductors, transistors and the section on Electromagnetic Compatibility, the last of which accounts for three questions in Section C. Remember, that's the one with just 10 questions and you need to get 6 of them right.

So I'll do my best to cover off some of those topics in the days ahead.

Congratulations to Michael from Kilkenny who tried the new sample paper and passed. Well done Michael. I look forward to meeting you in the Comreg offices!

Thursday, August 27, 2009

Propagation - some basics

Propagation will account for four questions in Section A. There are some basics which need to be known, starting with the ionospheric layers. The ionosphere is a region of the atmosphere between 100km and 400km above the surface of the Earth. It is above the troposphere, which is where all the clouds are located! The ionosphere is affected by radiation from the Sun, in the form of the Solar Wind. Air molecules are ionised, particularly by ultra violet radiation from the Sun. Solar flares can cause Aurora Borealis (Northern Lights) which can help with propagation of radio signals. Anyway, I'm distracting myself here. Back to the layers. You have to know these for the exam.

On right is a diagram of the ionosphere layers from the IRTS study CD.

What's important to note, apart from the heights they occupy, is that the D layer disappears at night, and the two F layers, F1 and F2, merge at around 250km above the earth. The F layer is at its weakest just prior to dawn.

The ionised regions of the atmosphere will reflect radio waves by refraction (gradual bending) within the layer.

The ionosphere is essential for long distance short wave radio communications.

As seen above, the layers will vary in height and density at different times of the day/night and different times of the year. One thing you MUST DEFINITELY KNOW about propagation is the length of the so-called "Sunspot Cycle". This is an 11-year cycle during which the number of sunspots on the surface of the Sun goes from maximum to minimum. Right now, we're in an extended minimum, with 0 sunspots. Things should pick up soon though and in a couple of years' time we should be experiencing great DX conditions if the solar activity increases.

Tropospheric propagation is for higher frequencies, usually above about 30-40Mhz.

Sporadic E propagation is more likely in the Summer, and affects the 2-metre band (144 - 146Mhz).

Ground Wave propagation: during the day, ground wave propagation is usable on frequencies up to approximately 2Mhz.

Some questions which have come up on QADV and elsewhere which need to be absorbed are as follows:

What is the mode of propagation called 'ducting' caused by:

a Refraction in the troposphere
b Variations in the earth's magnetic field
c Solar flares
d Absorption in the D region of the ionosphere.

The correct answer is a Refraction in the troposphere

The biggest daily variation in the maximum usable frequency occurs in:

a Spring
b Summer
c Autumn
d Winter

The correct answer is d Winter.

Monday, August 24, 2009

I passed! - the new sample paper, that is !

Right. There is a new sample paper online at the IRTS website. It is Revision 4, the previous one being Revision 3. Some of the questions are exactly the same, but there are a whole heap of new questions. I sat down and ran through the questions in about 20 minutes. Bear in mind that this is a bad idea, because in the real scenario you will have two hours, and that means time to spot some of the mistakes I made. I got one question on capacitance wrong because I worked it out the wrong way. Tut tut. And there was me telling everyone resistors and inductors are calculated the same way, but capacitors are the opposite.

Tony EI4DIB was here at the time and he reminded me of a handy mnemonic (I think that's what you call it) to remember what to do: think of the first four letters of capacitor - CAPA - and think of it thus:

C - Capacitor
A - Add
PA - PArallel

So, in parallel, add, and in series, it's C1xC2/C1+C2.

Anyhow, I managed to pass the whole exam, thankfully, so I am greatly encouraged now that my efforts are paying off.

I will try to give you some of the questions I got wrong, in the hope that (a) you don't make the same mistakes and (b) that I can better learn the correct answers.

I should have got this one right, but nevertheless I'll post it here so you can make sure you don't make the same mistake.

4. In the circuit below, ignoring component losses:

A [ ] Current at the resonant frequency and below that frequency will be unaffected
B [ ] Current at the resonant frequency will be impeded
C [ ] Current at the resonant frequency will readily pass through
D [ ] Current at the resonant frequency and above that frequency will be unaffected

The correct answer is B Current at the resonant frequency will be impeded. I answered C incorrectly.

9. A common-base amplifier, using a bipolar junction transistor, can be expected to have:

A [ ] High input impedance and high output impedance
B [ ] High input impedance and low output impedance
C [ ] Low input impedance and high output impedance
D [ ] Low input impedance and low output impedance

Having not done much at all on amplifiers, I simply didn't know the answer to this one. So I guessed. Wrongly. Now don't worry about a question throwing you off like that. I know it's daunting. But there is a margin for error. Remember that, even if you guess, you have a one in four (25%) chance of getting it right. In this case, I was wrong, but not to worry.

The correct answer is C Low input impedance and high output impedance.

13. The sensitivity of a receiver arises from:

A [ ] The bandwidth of the RF preamplifier
B [ ] The stability of the oscillator
C [ ] Its ability to receive weak signals
D [ ] Its ability to reject strong signals

I fell into the trap of thinking this was a trick question. I know that the sensitivity of a receiver is described as its ability to receive weak signals. It was the wording "arises from" that confused me. I needn't have been confused.

New Sample paper online now - Revision 4

Countdown Timer: 6 weeks 1 day to go

There is a brand new Sample Paper online now at the IRTS website. I am going to do it now and see how I get on. I'll let you know later on!

The Q codes - for Section B of the paper

Here is the list of Q codes given in the IRTS syllabus, which is included in the same document as the Sample Paper. Presumably these are the ones you need to know, rather than learning a more exhaustive list:

QRK What is the readability of my signals?
QRM Are you being interfered with?
QRN Are you troubled by static?
QRO Shall I increase transmitter power?
QRP Shall I decrease transmitter power?
QRT Shall I stop sending?
QRZ Who is calling me?
QRV Are you ready?
QSB Are my signals fading?
QSL Can you acknowledge receipt?
QSO Can you communicate with ... direct?
QSY Shall I change to transmission on another frequency?
QRX When will you call again?
QTH What is your position in latitude and longitude (or according to any other indication)?

Thursday, August 20, 2009

Some questions on safety for Section C of the paper

Countdown Timer: 6 weeks 5 days to go

Section C of the paper consists of questions on electromagnetic compatibility, safety and transmitter interference. Unlike the other sections, this is a short one, containing just 10 questions. But don't let that lull you into a false sense of security. There would be little point in achieving good scores in sections A & B if you only got five out of 10 right in section C, resulting in failure. With that in mind, it's well worth covering each topic as comprehensively as possible to avoid such a nasty scenario.

In the sample paper, the three questions which are asked were repeated in the June exam in one form or another, so let's have a quick look at what these questions entail.

58. Which of the following removes the mains supply when current flows to earth?

A [ ] Fuse
B [ ] MCB
C [ ] ELCB
D [ ] MMCB

The answer is (C) ELCB, which stands for Earth Leakage Circuit Breaker. Basically what this does is it cuts off the power supply within a fraction of a second "if the current flowing in the live and neutral become unequal by a preset amount (usually 30mA) which would happen if that amount of current flowed from live to earth". (Quoted from the IRTS Course CD)

59. The smoothing capacitors in a High Voltage supply for a valve power amplifier should have:

A [ ] A large value resistor to discharge the
capacitor when switched off
B [ ] Forced air-cooling
C [ ] A heat sink
D [ ] RF decoupling

Remember way back when we talked about the basics and compared a capacitor to a bin lorry? Like a bin lorry, which stores rubbish, a capacitor stores charge. Remember that one can receive an electric shock from the capacitors in equipment. (A) is the right answer above - a large value resistor to discharge the capacitor when switched off. You may be asked a variant of the above thus:

It is normal practice to discharge high voltage capacitors by:
A Short-circuiting them with a large toggle switch
B Switching a lower value capacitor in series with them
C Fitting a 'bleed resistor' in parallel with them
D Fitting a 'bleed resistor' in series with them

C is the right answer - fitting a 'bleed resistor' in parallel with them.

The last question on the sample paper, which was also asked in the June exam, is:

60. The human eye is most affected by radio frequency radiation at which frequency?
A [ ] 7 MHz
B [ ] 70 MHz
C [ ] 14 MHz
D [ ] 1270 MHz

The correct answer is D 1270 MHz. The human eye is most affected by RF radiation at microwave wavelengths.

There were one or two other questions which caught me out in the book "The Radio Amateurs Question & Answer Reference Manual" by R.E.G. Petri G8CCJ in the section on safety. I will give them here (a) to help me remember the right answer and (b) to help you identify the correct answer also.

12. When low-leakage capacitors are stored, you should:

a) pack them in a dry cardboard box
b) wrap their terminals with insulating tape
c) store them in a damp atmosphere
d) short circuit their terminals

I answered (b), which is incorrect. The correct answer is (d) short circuit their terminals.

13. In order to indicate that your equipment is live, you should-

a) fit a power output meter
b) make sure that it has suitable indicator lamps fitted
c) mount a thermometer on the transformer
d) fit a transformer with noisy laminations

I answered (a) but the correct answer is (b) make sure that it has suitable indicator lamps fitted.

16. When constructing equipment which uses high voltate, it is good practice to-

a) use low voltage fuses
b) use thermal delay fuses
c) fit micro-switches so that when any cover exposing high voltages is removed, the supply is disconnected
d) design a built-in SWR meter

The correct answer is c) fit micro-switches so that when any cover exposing high voltages is removed, the supply is disconnected.

25. For the measurement of high voltage circuits, you are warned not to use-

a) electronic voltmeters
b) spark-gap voltmeters
c) meters with metal zero adjusting screws
d) any of the above

The correct answer is (c) meters with metal zero adjusting screws.

28. A piece of radio equipment is rated 250 watts at 250 volts. What is a suitable fuse value for the mains supply?

a) 500mA b) 750mA c) 2A d) 13A

The correct answer is 2A. Just a bit of information from the IRTS Course CD in relation to fuse values:

Plug tops should have appropriately rated fuses fitted. Approximate values are
3A = 550 watts; 5A = 1100 watts;
13A = 2850 watts

I've just done 20 questions on safety using the QADV program and got 17 right out of 20, a total score of 85% ! Woohoo !

Wednesday, August 19, 2009

Country prefix codes - do you need to know them all?

Well, I'm no expert, as you know, having never taken the ham test in Ireland. However, one could surmise that the good people at IRTS and Comreg are not expecting you to have an encyclopedic knowledge of the prefix codes for the obscure nations and islands of the world. Perhaps you should stick to Europe and America, and maybe Russia?

Why? I hear you all ask. Well, on the sample paper you are asked in which country is the prefix LA (Norway) used. In the June exam it was CT (Portugal). So I guess one could deduce that a pattern is becoming obvious there.

It has to be said, in all fairness, that those of you who have been SWLs (Short Wave Listeners) for years will be at a distinct advantage on this front, but don't worry. I have been an SWL for a while but am still rusty on the prefixes. Let's give as good a list as possible for the European prefixes and try to learn these ones at least:

EI - Ireland
EJ - Islands of Ireland
GI - Northern Ireland
GD - Isle of Man
GM - Scotland
GW - Wales (easy one that - W for Wales!)
G - England
F - France (Couldn't be easier, eh?)
C3 - Andorra (not likely to be asked to be honest but I threw it in there anyway!)
EA - Spain (Think of EspanA - EA)
CT - Portugal
PA - Netherlands
ON - Belgium (for this one, I think of the Belgian port city of OosteNde)
LX - Luxembourg (one of those rare prefixes that is accurate to the country name!)
DL - Germany - think of "Deutchland"
OZ - Denmark
HB9 - Switzerland
HB0 - Liechtenstein
OE - Austria
OK - Czech Republic
SP - Poland
OM - Slovak Republic
HA - Hungary - HungAry
S5 - Slovenia
YO - Romania
LZ - Bulgaria
9A - Croatia
YU - Yugoslavia
Z3 - Macedonia
ZA - Albania
SV - Greece
SV9 - Crete
I - Italy (what could be simpler?!)
TK - Corsica
IS - Sardinia
9H - Malta
TF - Iceland
LA - Norway
SM - Sweden
OH - Finland
ES - Estonia (careful, don't confuse with Spain EA)
YL - Latvia
LY - Lithuania (Latvia the other way around!)
EU - Belarus
UR - Ukraine
UA - Russia

A very good website with an exhaustive list of ham country prefixes, but probably too detailed for the Irish ham exam, can be found here.

A good way to learn the prefixes is to listen in on the ham bands as an SWL and use a program like DX Atlas to look them up. DX Atlas is free to download. It's the one I use.

Don't forget that, in addition to the prefixes, you will need to know the Q codes. Again, I don't think you need to know an exhaustive list, but will post more about this later.

Exam fee received, so I'm booked !

Countdown timer: 6 weeks 6 days to go

Sean EI7CD has confirmed receipt of my exam fee, and says he will post on the requisite paperwork in due course. So I'm provisionally booked for the exam on Tuesday, October 6th. So now I have to make sure I'm ready !

Am unwell the past few days, hence the lack of activity. I hope to get back to action soon. I will post about prefixes later because these need to be known for Section B of the exam.

Saturday, August 15, 2009

Exam application and fee posted !

Countdown Timer: 7 weeks 3 days to go

Right, it's finally done. Something I should have perhaps done a couple of weeks ago. I have sent in my letter of application and fee for the exam.

I posted them yesterday by registered mail. Hopefully they will arrive into Sean's hands on Monday and I will have a place at the exam on October 6th.

The exam positions are booked on a first-come, first-served basis, and the closing date is September 21st. I figured it's best to get in there early. You don't feel the time flying by.

Thursday, August 13, 2009

Inductance - 7 out of 10 and some lessons learned

Countdown Timer: 7 weeks 5 days to go

I tried the 10 questions on inductance in John Bowyer's Towards the Radio Amateurs' Examination last night. I got 7 out of 10 right, and fell into a couple of traps, which I will try to highlight here in the hope you don't do the same thing.

But first, I must quote some of the introductory material on inductors to help familiarise you with some of the detail.

A circuit has a self-inductance of 1H if a rate of change of current of 1A/s in the inductor induces in it an e.m.f. of 1V.

The mutual inductance between two circuits is 1H if a change of current of 1A/s in one induces an e.m.f. of 1V in the other.

The inductance of a coil is proportional to its:

cross sectional area
the square of the number of turns
and inversely proportional to its wound length.

Assuming no mutual inductance, for inductors both in series and in parallel, the equivalent inductance may be found using similar expressions as with resistors. i.e.:

Series: R1+R2 - L1+L2 Parallel: R1xR2/R1+R2 - L1xL2/L1+L2

All inductors possess resistance. When an inductor is connected across a d.c. supply, the current takes a finite time to reach its final value of V/R. The time constant is an indication of the rise of this current.

Here are two of the three questions I got wrong:

9. Two coils, each of an inductance of 4mH, are connected in series. Their combined inductance
a is 12mH
b is 8mH
c is 2mH
d could be either 2mH, 8mH or 12 mH

Two inductors in series are added, like resistors. So 4 milli henrys plus 4mH = 8mH, right? Yes, but this is the wrong answer, because, as the book explains:

It cannot be assumed that there is no mutual inductance. The combined inductance is not necessarily 8mH.

So d is in fact the correct answer.

10. Two inductors are mutually coupled, and the distance between them gradually increased. Their mutual inductance will
a increase
b remain the same
c decrease
d be immediately zero

I simply didn't know the answer to this question, so I guessed that it would remain the same. The correct answer, however, is c, and this is explained thus:

As the distance between the two inductors is increased, their effect on each other (mutual inductance) will decrease.

Wednesday, August 12, 2009

Batteries - external voltage

A quick aside on batteries - we will return to inductance tomorrow.

This from Wikibooks:

Vexternal = E - Vinternal

Since V = IR:

Vexternal = E - IRinternal

You may also need to use the following formula to work out the external potential difference, if you are not given it:

Vexternal = IΣRexternal

You should also remember the effects of using resistors in both series and parallel circuits.

The reason I'm posting this here is to remind me to learn it !!

Capacitance - taking things on a step further

Countdown Timer: 7 weeks 6 days to go

You remember we touched on capacitors, and storing charge, and bin lorries? That was just over two weeks ago - read it here if you need to refresh your memory. Well now we're going to take things on a step.

I learned a very valuable lesson in Brian's QTH on Monday night which has helped me solve some capacitance questions quite easily. Here it is, so read carefully and take it in:

With resistors, when in series add them up, when in parallel, its R1xR2/R1+R2. Got that? Basic Ohm's law stuff.

Well, with capacitors, it's the OPPOSITE!

When in series, its C1xC2/C1+C2

And when in parallel, you add their values.

This basic knowledge helped me answer another question on the Sample Paper, which I present below:

We see that capacitors C2 and C3 are in series, so we need to work out their overall capacitance by using: C2xC3 / C2+C3 = 20x20/20+20 = 400/40 = 10. So 10 nF is the overall capacitance of C2 and C3. They are in parallel with C1, so we just add 10 to the value of C1, which is 5 nF, giving 15 nF.

So B - 15 nF - is the correct answer.

I now have in my possession another book, called "towards the Radio Amateurs' Examination" by John Bowyer, published by Stam Press Limited. I tried the 10 questions on capacitance and excelled myself by getting 9 out of 10 or 90%. I will give some examples here.

1. The parallel plates of a capacitor are separated by 2mm of air. If this separation is increased to 4mm, the new value of capacitance will be:

a four times the original capacitance
b double the original capacitance
c one-half the original capacitance
d one-quarter the original capacitance

I knew, having read it, that the capacitance reduces as the distance between the plates increases, but this is actually expressed in the formula:

Capacitance of a capacitor = permittivity x plate area / distance between plates

otherwise expressed as 1 / distance between plates

Therefore, if the distance is doubled, then C must be halved. So the answer is (c).

2. Two capacitors, of value 10 µF and 40 µF respectively, are connected in series. An equivalent capacitor will have a value of:

a 8 µF
b 30 µF
c 50 µF
d 400 µF

Remember that with capacitors it's the opposite to resistors, so when capacitors are in series, we use C1xC2/C1+C2, so 10x40/10+40 = 400/50 = 8.

The answer is (a) 8 µF !

Tuesday, August 11, 2009

Resonance - the tight-rope walk, blindfolded !

I've no idea why, but for some reason I've started with resonance, and the resonant frequency of a circuit. It's like trying to learn to walk by doing a tight-rope walk blindfolded between to skyscrapers.

And although I think I've learned the formula fairly quickly - f equals 1 over two by pi by the square root of LC, where L = inductance in Henrys and C is capacitance in Farads, I struggled since yesterday to get the correct answer in one of the questions on the sample paper.

After much perseverance, scratching of heads and pushing calculator buttons, I finally worked out the correct answer. I'll tell you how and where I went wrong . . .

But first, I have to pop up to Tony's to collect a book, so I'll continue later.

Right, I'm back. Me and Tony had a good old chinwag. Took me two hours to collect the book, and he only lives 5 minutes away !!

Anyhow, here's the question in the Sample Paper which I attempted to answer:

In the circuit below, given that L = 100 μH, C = 150 nF, what is the resonant frequency of the circuit? This is question 9 in the sample paper.

OK, so when I originally set about to answer it, I got an answer which wasn't any of the four options outlined below:

A [ ] 410.94kHz
B [ ] 41.094 kHz
C [ ] 4.1094 kHz
D [ ] 0.41094 kHz

Right, so we start with the inductance (L) which is 100 μH. One μH (micro henry) is .000001 Henrys. So that's .0001 H. The capacitance (C) is 150 nF or nano Farads. One nano Farad nF is .000000001, so 150 nF is .00000015 F. Remember I gave you the Micro, Nano, Pica equivalents in the section on capacitors? OK, if you can't then just remember the number of decimal places - micro (μ) = .000001 (6 places), nano (n) = .000000001 (9 places) and pica (p) = .000000000001 (12 places).

So the first thing we need to do is multiply LxC. .0001 x .00000015 is 0.000000000015 or otherwise, as the scientific calculator gives it, 1.5 x 10 to the power of minus 11.

Now we need the square root of 0.000000000015 which is .000003872.

Now, I know what you're thinking. Probably the same thing I was thinking. "This looks like it's going wrong. How the heck can I be on the right track with such tiny fractions of numbers?" Yes, I very much doubted where I was going with this. But stick with me.

The next stage is to find the value of two by pi. Now the value of pi given by the scientific calculator is 3.141592654, and this is where things started to go wrong for me. I'll explain why in a minute. Multiplying this pi value by 2 gives 6.283185307. This is further multiplied by .000003872 (square root of L x C). Still with me? Hope so! That gives .000024328. And one over .000024328 gives 41104. That's the frequency (f) in Hertz. 1,000 Hz is 1 kHz. So 41.104kHz is the answer But our answer is not given in the list:

A [ ] 410.94kHz
B [ ] 41.094 kHz
C [ ] 4.1094 kHz
D [ ] 0.41094 kHz

Answer B - 41.094 kHz looks close, but were' 10 Hz out. How come? I racked my brains over this one for an hour this evening - even had my wife Ann helping out. Turns out that it's so long since I did formulae or any sort of complex maths that I haven't a clue how to do all this stuff. So I let the scientific calculator do the work.

After getting LxC = .000003872, I multiplied by pi then by 2, which gives .000024334 (remember previously we got .000024328 - well those six billionths make all the difference!!) One over .000024334 gives 41.093.6

41093.6 rounded up is 41094 Hertz. That's 41.094 kHz. So we now know the true answer is B. It took a good while but we got there. Phew! Questions welcome if you are stuck on any of this. Remember, I'm doing this for the first time too, so if you're stuck I can only promise encouragement !

The task ahead - six subject headings to learn

Countdown Timer: 8 weeks 0 days to go

Right, I'm just back from Brian EI7GVB's house and he's set me a stern task for the next couple of weeks to help me through the first 12 questions of Section A. Here are the subjects I have to learn about, and the associated formulae:

Capacitive Reactance
Inductive Reactance

Who ever said this was going to be easy?

To help me in this task, Brian has suggested I answer as many questions as possible in a book which I have borrowed from the Dundalk Amateur Radio Society. This book is called The Radio Amateurs' Question & Answer Reference Manual by R.E.G. Petri, published in 1984. Link

I'll give it a go. Lots to do, lots to learn. Lots of study required.

On a lighter note, we worked for about 45 minutes on 40 metres and got 20 nice contacts into Europe.

Lots of study ahead . . .

Monday, August 10, 2009

It's official - Section B to be based on new legislation

Countdown Timer: 8 weeks 1 day

It's official - the section on National and International Rules and
Operating Procedures - is to be based upon the legislation which came into effect in June of this year. The official title of the new legislation is the Wireless Telegraphy (Amateur
Station Licence) Regulations 2009. Here is some information about the exam which was read out on last week's IRTS news:

Next Theory Examination

The next Theory Examination for the Amateur Station Licence will be held on Tuesday the 6th of October at 2p.m. in the ComReg Offices in Dublin. Places for the examination are limited and will, as usual, be allocated on a first come first served basis and will only be reserved on receipt of the examination fee.
Intending candidates should forward the appropriate fee to Sean Nolan EI7CD, 12 Little Meadow, Pottery Road, Dunlaoghaire, Co. Dublin in order to reserve a place for the exam.

The fee is 50 Euro or 25 Euro for full-time registered students, repeat candidates and those who are retired, unemployed or have a disability. Cheques and Money Orders should be made payable to the IRTS. When forwarding the exam fee intending candidates should enclose their postal address as well as phone and e-mail contact details.

The closing date for applications to sit the examination, which will be strictly enforced, is Monday the 21st of September. Intending candidates should note that anyone who fails to produce a photo identity on the day of the examination will not be allowed to sit the examination. The photo ID can be a driving licence, a passport, an employment photo identity card or a student card containing a photograph. A national Garda photo ID would also be acceptable.

Sean EI7CDs address can also be found in the IRTS call book or in the call book section of the IRTS website at Sean's e-mail address for any further enquiries is “ei7cd at gofree dot indigo dot ie” Also available on the ‘Downloads’ section of the IRTS website are Examination Notes with a sample examination paper. Also, in the Radio Theory Links section on the website is some very useful information for those studying for the examination.

The examination consists of a question paper of 60 multiple-choice questions divided into three main sections A, B and C and the time allowed is two hours. The pass mark is 60% and a pass is required in each of the three main sections of the paper. Intending candidates should note in particular, that in Section B of the paper – National and International Rules and Operating Procedures’- questions on the National Rules will be based on the new Wireless Telegraphy (Amateur Station Licence) Regulations 2009 which came into force on I June 2009.

These Regulations and other matters in relation to the operation of amateur stations can be found in the ‘Amateur Station Licence Guidelines’ published by ComReg in Document 09/45 which is available on the ‘Publications’ section of the ComReg website at

Saturday, August 8, 2009

Can anyone make sense of this?

I was just perusing the Statutory Instrument , introduced on June 1st, governing the Amateur Station Licence. For those interested, you can find it here. You will need to read this document and understand it for the test on October 6th.

Anyhow, therein, I found the following paragraph, and if you can make sense of it, fair play. I'd like to know what it means . . .

a reference to a Regulation or a Schedule is to a Regulation of, or a
Schedule to, these Regulations, unless it is indicated that reference to
some other enactment is intended;

Suggestions as to its meaning are welcome.

In the meantime, I've received clarification on which regulations form the basis of Section B in the October test, which I will post more about later.

Friday, August 7, 2009

Basic electronics - Inductors and Inductance

Right, we've done a little bit so far on resistors, capacitors and diodes, so today we're going to move on to Inductors and Inductance to help us with that huge chunk of section A, those 12 questions which we need to know this stuff for.

After a quick Google search, I came up with a website that seems to explain things in very simple language. The website is Here is a direct quote from that website:

An inductor is about as simple as an electronic component can get -- it is simply a coil of wire. It turns out, however, that a coil of wire can do some very interesting things because of the magnetic properties of a coil.

Great. So an inductor is a coil of wire. Simple eh?

An inductor is an electromagnet. An inductor resists a change in the flow of electrons. You can think of an inductor in terms of a large water wheel with its paddles dipping into a narrow water channel.
Now you try to start the water flowing. The paddle wheel will tend to prevent the water from flowing until it has come up to speed with the water. If you then try to stop the flow of water in the channel, the spinning water wheel will try to keep the water moving until its speed of rotation slows back down to the speed of the water.
The capacity of an inductor is influenced by four things:

* The number of coils - More coils means more inductance.
* The material that the coils are wrapped around (the core)
* The cross-sectional area of the coil - More area means more inductance.
* The length of the coil - A short coil means narrower (or overlapping) coils, which means more inductance.

The Unit of Inductance is the Henry.

It would be helpful at this point to look at Faraday's Law (remember him, and the unit of capacitance, the Farad?)

Faraday's Law states that:

Any change in the magnetic environment of a coil of wire will cause a voltage (emf) to be "induced" in the coil. No matter how the change is produced, the voltage will be generated. The change could be produced by changing the magnetic field strength, moving a magnet toward or away from the coil, moving the coil into or out of the magnetic field, rotating the coil relative to the magnet, etc.

To help us further understand what an inductor does, we'll look up the word inductance in the dictionary:

that property of a circuit by which a change in current induces, by electromagnetic induction, an electromotive force.

So we're getting the picture. Let's just have a look at the IRTS disk before moving on to the next subject.

Any wire carrying a current is surrounded by a magnetic field; winding the wire into a coil strengthens this field
•When the current changes, the magnetic field changes inducing a back emf in the coil that opposes the change in current. This phenomenon is called self inductance
•The unit of inductance is the Henry (H) but as this is a large unit the milli- and micro-Henry (mH, mH) are more commonly used

OK, we're going to let that sink in because there's a wee bit more to study on inductors before we move on.

Sample paper attempted - not a bad result - plus a warning

Countdown timer: 8 weeks 4 days to go

Right, I gave the IRTS exam Sample Paper a go last night, even with my limited study and lack of knowledge. I had to guess some answers (I guessed right in more than 50% of cases) and I had to leave some blank. I only answered four out of 12 questions in the electronics and circuitry section because I haven't studied most of that yet. I was surprised at my results, which were as follows:

Section A - 20 questions right out of 35 - 57% - Nearly a pass
(In fact, when I guessed another question I got it right, putting me over the 60%)
Section B - 12 questions out of 15 correct - 80 % - Pass

Section C - Only four questions attempted out of 10, but got them right. 40%. Not enough for a pass yet!

Remember that you have to get at least 60% in ALL THREE sections in order to pass the exam. Right now it looks like I need to concentrate most on sections A and C.

Just something to note - BEWARE THE PITFALLS - there are some tricky questions. For instance, I came upon this question:

42. The maximum power output permitted from a
radio experimenter’s station is:
A [ ] Specified in the schedule attached to
the radio experimenter’s licence
B [ ] 400 watts
C [ ] 600 watts
D [ ] The minimum needed to enable the
experimenter to be heard

I was damn certain, 100% sure, that B was the right answer, because no radio amateur is allowed to exceed 400 watts power output. However, the correct answer is A - and that is because your power output depends on the band and mode being worked, and the limits are specified in the schedule attached to your licence. So that was one I thought "I absolutely got right" but which turned out otherwise.

Another question which came up was one I was able to answer based on the Transmitters Basics post I made on Tuesday. Remember that FM has the widest bandwidth, followed by AM, followed by SSB, followed by CW, which is the narrowest. Here's the question:

14. SSB transmissions:
A [ ] Occupy about twice the bandwidth of
AM transmissions
B [ ] Contain more information than AM
C [ ] Occupy the same bandwidth as CW
D [ ] Occupy about half the bandwidth of
AM transmissions

And of course, based on the simple knowledge about Wide to Narrow, FM AM SSB CW, we know that the answer has to be D. And that's the right answer!

Just in case you didn't know, all the correct answers are given at the end of the Sample Paper. But don't look before you give the questions a try !

I am grateful for the assistance of my wife, Ann, who is encouraging me through this process. She helped de-stress the situation last night and we were both surprised and delighted with the results so far.

Wednesday, August 5, 2009

The exam - 60 questions in sections

Countdown Timer: 8 weeks 6 days to go

OK, Brian is unavailable for study tonight and so is Tony. So I'm looking at the exam format and the things I need to learn. There are 60 questions in total, with a set breakdown as follows:

Section A - Elementary Theory of Radiocommunications (35 Questions)
· Electrical and Electronic Principles and Circuits – 12 Questions
· Transmitters and Receivers – 10 Questions
· Feeders and Antennas – 5 Questions
· Propagation – 4 Questions
· Measurements – 4 Questions

Section B - National and International Rules and Operating Procedures (15 Questions)
· Licensing Conditions – 7 Questions
· Operating Rules and Procedures – 8 Questions

Section C - Safety and Electromagnetic Compatibility (10 Questions)
· Electromagnetic Compatibility – 4 Questions
· Transmitter Interference – 3 Questions
· Safety – 3 Questions

Now if we look at that in a relaxed and positive light, we see that, for instance, there are ten questions about Transmitters and Receivers. I've already covered receivers and have started on transmitters. If I cover that properly, I am ready to answer ONE SIXTH of the total questions in the exam. That's 2 modules out of 15 which covers 16.6% of the exam. Wow!! So, the advice from me right now is, Don't Panic!

Easier said than done, you say. Especially if, like me, you're not comfortable with the amount of study done (or not done!) on the "biggie", ie 12 questions on Electrical and Electronic Principles and Circuits. Of course that makes one fifth of the total or 20%. So, if you can get your study done and get your head around the first two items - electronics and circuits, and transmitters and receivers, you'll be in a position to answer 36.6% of all the questions. Nice.

For Section B, there are three important documents which you should access, download, print off and study. I have just printed them off and now need to get stuck into them. They are:

Radio Experimenters Handbook - download here

Particulars of Experimenters Station - download here

Technical Conditions of Experimenter's Station - download here

Also, you should study the band plans, as you will DEFINITELY be asked a question on this. For instance, in the sample paper, the question is as follows:

Under the Band Plan applicable to Ireland,
which modes permitted under licence
regulations may be used in the frequency
range 14.000 – 14.060 MHz:
A [ ] All modes
B [ ] Telegraphy (CW) only
C [ ] Telegraphy (CW) and Telephony only
D [ ] Telephony only

You can download, print off and study the IARU Region 1 HF Band Plan chart from the IRTS website. Of course, don't forget to look at the VHF/UHF band plan also.

And remember, if all this looks daunting right now, remember that Brian EI7GVB did all the study for his exam in seven weeks! (OK, he had been a Short Wave Listener for many years and was familiar enough with band plans and international prefixes etc).

One strong piece of advice is to download and print off the sample paper, which will give you a good feel for the exam. The Sample Paper can be found here.

For now, I'm going to have another look at transmitters. The sooner I cover that off the better. That will make me ready for 16.6% of the exam.

Tuesday, August 4, 2009

Transmitters - let's start with the basics

Right, time to knuckle down for some more study. We've covered receivers quite well, so time to look at the transmitter. It's worth bearing in mind that of the 60 questions in the exam, 35 are in section A, and of those 35, a total of 10 are about transmitters and receivers. In other words, this accounts for one sixth of the questions in the entire exam, so these are two modules worth covering in detail and learning inside out. Remember to answer 30 questions in the QADV program when you've done your study and keep doing so until you get a score of 90% or better.

The IRTS disk starts with the different modulation modes, and there are five of these, as follows:


CW is Continuous Wave, and occupies a narrow bandwidth. It is transmitted through an on-off Morse Key

AM stands for Amplitude Modulation. The output amplitude varies according to the amplitude of the modulating signal. The original carrier and two side bands are transmitted. AM occupies a bandwidth which is the equivalent of twice the modulating frequency. There is a lot of power in the carrier.

SSB is (Amplitude Modulation) Single Side Band - where the carrier is suppressed, in most cases by a balanced modulator. One sideband is suppressed by a filter. SSB occupies half the bandwidth of AM. As there is no carrier, all the power is in the side band, making SSB more efficient.

FM stands for Frequency Modulation. The deviation of the output frequency is proportional to the amplitude of the modulating signal. The amplitude of the carrier is constant.

You can read a bit more about modulating methods on this website.

Just a little bit about bandwidth which is skipping a bit but you will definitely be asked at least one, possibly two questions about this. In the June exam, candidates were asked which bandwidth was best for CW and also, I think, a question asking how much wider an AM bandwidth was compared to CW.

IRTS says: "The bandwidth of a signal is determined by mode and by audio"

FM is widest.
AM is next
SSB is next
CW is narrowest.

The official document from IRTS - Anthony Murphy EI1597

Here it is, the official letter from Sean Donelan EI4GK welcoming me to the Irish Radio Transmitters Society and bestowing upon me my new SWL (Short Wave Listener) Identification Number EI1597. At long last, the world can know I listen to HF radio!!

I can't remember the exact year I first listened to HF, but if you consider I worked 11 metres (27 Mhz) in my late teens and I'm now 35, I suppose that would make it 17 or 18 years. It's about time I joined a society really, isn't it? . . .

Anyhow, time is pressing on. I'm exhausted with everything that's going on (including a leak in the back room of my house, which is my radio/computer shack) but I must do some study. Even a little bit tonight. I'm going to try transmitters. Brian EI7GVB had told me to do receivers and transmitters before our next hook-up, which is tomorrow. I've covered receivers pretty well, but not transmitters. I'll get a small bit done now but I'm going to be busy tomorrow and Thursday so we'll see how things go.

Right, I printed out the module from the IRTS disk about transmitters, so I'll go and have a read and post any salient information here in my next deliberation . . .

Nine weeks to go - and more study needed

Countdown: 9 weeks 0 days to go

I just heard on the IRTS news through the Dundalk Repeater yesterday evening (145.675) that 30 people took the Irish ham test in June and 16 passed. That's just a midget's whisker over 50%. Congratulations to all who passed and good luck to those who failed who are re-sitting the test in October.

I haven't done any study for a few days what with one thing and another. The plan is to go to Brian's house Wednesday evening for some study on capacitance and inductance. Tony had the flu last week so we never started on electronics, but not to worry. We'll catch up on it when he's feeling better.

Must get the head into the books again . . .

Also, need to send in the 50 euro fee for the exam. First come, first served and all that!