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TelecommunicationsTelecommunications

TelegraphyTelegraphy

RadioRadio

AntennasAntennas

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Who we are ...Who we are ...

– Dr. David Conn (VE3KL)Dr. David Conn (VE3KL)

– Dr. Ken Pulfer (VE3PU)Dr. Ken Pulfer (VE3PU)

– Bryan Rawlings (VE3QN)Bryan Rawlings (VE3QN)

• And, we are all And, we are all Radio AmateursRadio Amateurs23-04-21 2

ImagineImagine

• It’s 1840, you are in Ottawa and It’s 1840, you are in Ottawa and you want to send a message to a you want to send a message to a friend in Montréal …friend in Montréal …

• No telephoneNo telephone• No cellphonesNo cellphones• No InternetNo Internet• No No FacebookFacebook or or TwitterTwitter

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““Instant Messaging” Instant Messaging” – 1840 version– 1840 version

• write your friend a messagewrite your friend a message– with pen and paperwith pen and paper

• take it to the Post Officetake it to the Post Office– carried to Montréal by horse and carriagecarried to Montréal by horse and carriage– arrives a few days laterarrives a few days later

• reply comes back the same wayreply comes back the same way

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Then, A Marvellous InventionThen, A Marvellous Invention

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• The electric telegraph !!The electric telegraph !!

The Morse CodeThe Morse Code

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Next, Wireless !!Next, Wireless !!

7

Heinrich Hertz

Guglielimo Marconi

James Clark Maxwell

How They Did It …How They Did It …

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• This is a diagram of an old spark-gap radio This is a diagram of an old spark-gap radio transmitter …transmitter …

Early Radio was weird !Early Radio was weird !

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Radio Waves – the long Radio Waves – the long and the shortand the short

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wavele

ngth

Do you know what a Do you know what a HertzHertz is? is?

• No! It’s not a rental car!No! It’s not a rental car!– not today, anywaynot today, anyway

• It’s the unit of It’s the unit of frequencyfrequency– one one HertzHertz = one cycle-per-second = one cycle-per-second

• It’s named after Heinrich Hertz, the It’s named after Heinrich Hertz, the scientist who first demonstrated radio scientist who first demonstrated radio waveswaves

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Frequencies and WavelengthsFrequencies and Wavelengths

• Frequency and wavelengths go togetherFrequency and wavelengths go together– Like soap and water (or whatever)Like soap and water (or whatever)

• ““low” frequency > long wavelengthlow” frequency > long wavelength– CFRA: 580 kiloHertz – 500 metresCFRA: 580 kiloHertz – 500 metres

• ““high” frequency > short wavelengthhigh” frequency > short wavelength– Magic-100 Magic-100 : 100.3 MegaHertz – 3 metres: 100.3 MegaHertz – 3 metres

• Hint: divide speed of light by frequency Hint: divide speed of light by frequency to get wavelengthto get wavelength

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The Antenna …The Antenna …makes it happen !makes it happen !

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Keep It SimpleKeep It Simple- the dipole- the dipole

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The simplest antenna is called a “dipole”. It is one-half wavelength long and connected to the transmitter/receiver at its center.

The AntennaThe Antenna

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This big antenna – This big antenna – about 125 metres high about 125 metres high – is used to transmit – is used to transmit radio waves at a radio waves at a frequency of 650 frequency of 650 kiloHertz. It is used by kiloHertz. It is used by AM radio station WSM AM radio station WSM in Nashville TN.in Nashville TN.

A part of the antenna A part of the antenna is in the ground.is in the ground.

Will that be horizontal or Will that be horizontal or vertical?vertical?

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You will see lots of these !You will see lots of these !

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These are the antennas at cellular radio sites.These are the antennas at cellular radio sites.Which way are they polarized?Which way are they polarized?

Not many of these anymore !Not many of these anymore !

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This is an off-the-air television antennaThis is an off-the-air television antenna.

Directional AntennasDirectional Antennas

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These radio waves go to the leftThese radio waves go to the left

This is an antenna, tooThis is an antenna, too

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Do you know where the “antenna” is?Do you know where the “antenna” is?

What’s a “Yagi” ?What’s a “Yagi” ?

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The elements of this antenna are about 10m longThe elements of this antenna are about 10m long

A Smaller Yagi AntennaA Smaller Yagi Antenna

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The elements of this antenna are about 35 cm longThe elements of this antenna are about 35 cm long

One More Yagi BeamOne More Yagi Beam

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Three beam antennas on one boomThree beam antennas on one boom. At EI4IS overlooking Cork harbourAt EI4IS overlooking Cork harbour.

Let’s Assemble an AntennaLet’s Assemble an Antenna

Now, we’re going to take a few Now, we’re going to take a few moments to put together a small moments to put together a small Yagi beam antenna which is Yagi beam antenna which is designed to operate at 144 designed to operate at 144 megaHertz.megaHertz.

So, its elements are just about So, its elements are just about one metre long.one metre long.

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Thank You!Thank You!

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