Andrew Vine, M0GJH
Amateur radio
Recall that the amateur licence is for self-training in radio communications and is of a non-commercial nature.
Nature of amateur radio
Licensing Conditions
Types of Amateur Licence
Foundation
Intermediate
Advanced
Recall the format of the current Foundation, Intermediate and Full call signs.
Format of Amateur call signs
M3ABC
2E0ABC
M0ABC
Know the Regional Secondary Identifiers and how they are used with a Foundation licence.
D
I
M
W
J
U
Isle of Man
Northern Ireland
Scotland
Wales
Jersey
Guernsey
M3ABC becomes Mx3ABC where x = D, I, M etc
Note, there is no Regional Secondary Identifier for England
Mobile and Portable operation
/ P - e.g. MW3ABC/P
/ M - e.g M3ABC / M
A typical question
Your call sign is M3ABC. You go to the Isle of Man on holiday and want to operate from your holiday accommodation. What call sign do you use ?
MD3ABC / P
You live in Scotland and your callsign is MM3ABC. On a visit to England you want to operate with a hand held set whilst walking in the Lake district.
What call sign do you use ?
M3ABC / M
The CQ Call
CQ CQ CQ CQ CQ CQ
This is M3ABC, M3ABC calling CQ CQ CQ
This is M3ABC calling CQ and standing by
Recall the requirements for station identification.
During initial CQ Calls
At beginning and end of each period of communication
After 15 minutes
Transmission on a new frequency
By same type of transmission and on same frequency
Only send messages to other amateurs.
Some do’s and don’ts
No secret codes
No broadcasting
No transmission of music
Only the licensee personally may use the station.
Must notify Ofcom of change of address.
Ofcom local office officials have the right to close down or restrict operation.
Some do’s and don’ts
Ofcom is the independent regulator and competition authority for the UK communications industries, with responsibilities across television, radio, telecommunications and wireless communications services
The Log Book
Date
Time (UTC) of :-
first transmissionlast transmissionChanges to frequency, band, class or power
Frequency or Band
Mode
Power
The Log Book
Initial CQ Calls
Call signs of stations worked
Location when at a temporary location
Need to be able to interpret :-
The Schedule to the Licence
Band Plans
Frequency Allocation Table
Technical Basics
Identify the units of, and abbreviations for, Voltage (Potential Difference), Current, Power and Resistance.
& OhmsVolts, Amps, Watts
Note: Prefixes milli, kilo and Mega may be used.
Recall the relationship between Voltage (Potential difference), Current and Power
Power = Volts x Amps
W = V x A
Recall the relationship between Voltage (Potential difference), Current and Resistance
Volts = Amps x Resistance
V = I x R
Batteries
Polarity can be important
Direct Current / Alternating Current (DC / AC)
AC easier to generate and change voltage
Frequency
mains supply
UHF
VHF
HF
normal hearing
audio communication
50Hz (230 volts)
100Hz - 15kHz
300Hz - 3kHz
3MHz – 30MHz
30MHz – 300MHz
300MHz – 3000MHz
Frequency Allocation Table (discuss chart)
Frequency and Wavelength (discuss chart)
No need to know c = f x λ at this level
Transmitters and Receivers
1 2
3
4
Audio Stage
Modulator
Frequency Generator
RF power amplifier
frequency generation stage(s) (e.g. oscillator(s)) in a transmitter defines the frequency on which the transmitter operates.
incorrect setting of these stages can result in operation outside the amateur band and interference to other users
Need to remember
audio (or data) signal is modulated on to the radio frequency “carrier” in the modulation stage of the transmitter
FM AM
Common modulation modes :-
AM Carrier and two side bands
SSB Single side band
FM
Voice
Frequency Modulation
Morse code Carrier
Data Frequency Shift Keying (FSK) on SSB or FM
Transmitter considerations
the r.f. power amplifier output must be connected to a correctly matched antenna to work properly and that use of the wrong antenna can result in damage to the transmitter
excessive amplitude modulation causes distorted output and interference to adjacent channels
excessive frequency deviation will cause interference to adjacent channels
need to ensure that the microphone gain (where fitted) is correctly adjusted
1 2
Tuning and rf amplifier
Detection
Audio amplifier
The Receiver
3
Loudspeaker
Feeder requirements
Need to use the correct cable for r.f. signals. Coaxial cable is most widely used because of its screening properties
plugs and sockets for r.f. should be of the correct type and that the braid of coaxial cable must be correctly connected to minimise r.f. signals getting into or out of the cable.
Plugs
BNC
PL259
Antennas
the purpose of an antenna is to convert electrical signals into radio waves, and vice-versa.
¼ λ ¼ λ
½ wave dipole
λ/4 groundplane
5/8 λ
Yagi
Polarisation ?
Radiation pattern ?
Some more antennas
Long Wire
10W Gain 10 dB 100W
= erp
Effective Radiated Power (“erp”)
Gain in dB = 10Log10 (Power Out)
(Power In)
3 dB = 2 times 6 dB = 4 times 9 dB = 8 times
10 dB = 10 times
If an antenna is not correctly designed for the frequency it will not match the transmitter and will not work effectively
Points on Antennas
Where an antenna has not been designed for the particular frequency, an ATU (antenna tuning unit) makes it possible for the antenna to accept power from the transmitter.
Balanced and unbalanced
¼ λ ¼ λ
Balanced and unbalanced
¼ λ ¼ λ
Balun
Standing Wave Ratio
¼ λ¼ λ
i v
The amplitude of the standing wave varies between a minimum and maximum. The ratio of the maximum to minimum value is known as the voltage standing wave ratio (VSWR) or standing wave ratio (SWR).
6 7 8
SWR v Frequency for a dipole 20.22m in length
A high SWR (measured at the transmitter) is an indication of a fault in the antenna or feeder (and not the transmitter
SWR
Dummy Loads
50 ohm dummy load
10 x 1W resistors
Each resistor = 500Ω
Radio propagation basics
radio waves travel in straight lines, unless diffracted or reflected.
radio waves get weaker as they spread out (inverse square law)
v.h.f. and u.h.f. hills cause “shadows” and waves get weaker when penetrating buildings but glass windows are more transparent to radio waves
Radio propagation basics
range achieved at v.h.f./u.h.f. is dependent on antenna height, a clear path and transmitter power.
Higher antennas are preferable to higher power, as they improve both transmit and receive performance.
Outdoor antennas will perform better than indoor antennas.
at v.h.f./u.h.f., range decreases as frequency increases and that in general, v.h.f./u.h.f. waves have a range not much beyond “line of sight
Ionosphere basics
70 Km
400 Km
Electrons are stripped off the gas molecules, resulting in ions, by the ultra-violet radiation of the Sun as well as incident X-rays
On h.f. almost all communication relies on the waves being reflected by the ionosphere. H.f. can provide world-wide propagation depending on how well the ionosphere bends the waves back to the earth. This varies with frequency, time of day and season.
400 Km
70 Km
Ionosphere basics
EMC Electro magnetic Compatibility
the avoidance of interference between various pieces of electronic equipment
radio transmitters can cause interference to nearby electronic and radio equipment
radio receivers can also suffer from interference from local sources
interference occurs through local radio transmissions being conveyed to the affected equipment through pick up in house wiring, TV antenna down-leads, telephone wiring etc., and (particularly at v.h.f./u.h.f.) by direct pick-up in the internal circuits of the affected equipment itself.
EMC
Chelmsford Slides
Operating practices
How to make a CQ call - HF
1) Listen
2) Check that the frequency is not being used
3) Call CQ
Operating practices
How to make a CQ call - VHF
1) Find a channel that is not being used
2) Switch to the calling channel
3) Listen and then ask if the frequency is in use
4) Call CQ
5) Having established contact switch to a vacant channel
Operating practices – need to know
Phonetic alphabet
What repeaters are about ?
Why Band Plans are used ?
Connecting anything other than the supplied microphone (e.g. packet radio, TNCs) to the transmitter requires correct operation of the PTT line and correct audio signal levels.
Phonetic Alphabet
SierraTangoUniformVictorWhiskeyXrayYankeeZulu
AlphaBravoCharlieDeltaEchoFoxtrotGolfHotelIndia
Juliet KiloLimaMikeNovemberOscarPapaQuebecRomeo
Repeaters
Output Frequency 433.300 MHz
Input Frequency 434.900 MHz
Access 1750Hz initial access
GB3GF
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