Transcript Document

Andrew Vine, M0GJH
Amateur radio
Nature of amateur radio
Recall that the amateur licence is for self-training
in radio communications and is of a noncommercial nature.
Licensing Conditions
Types of Amateur Licence
Foundation
Intermediate
Advanced
Format of Amateur call signs
Recall the format of the current Foundation,
Intermediate and Full call signs.
M3ABC
2E0ABC
M0ABC
Know the Regional Secondary Identifiers and how they
are used with a Foundation licence.
D
Isle of Man
I
Northern Ireland
M
Scotland
W
Wales
J
Jersey
U
Guernsey
Note, there is no Regional Secondary Identifier for England
M3ABC becomes Mx3ABC where x = D, I, M etc
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
Some do’s and don’ts
Only send messages to other amateurs.
No secret codes
No broadcasting
No transmission of music
Some do’s and don’ts
Only the licensee personally may use the station.
Must notify Ofcom of change of address.
Ofcom is the independent regulator and competition authority for the
UK communications industries, with responsibilities across television,
radio, telecommunications and wireless communications services
Ofcom local office officials have the right to close
down or restrict operation.
The Log Book
Date
Time (UTC) of :first transmission
last transmission
Changes 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.
Volts, Amps, Watts & Ohms
Note: Prefixes milli, kilo and Mega may be used.
Recall the relationship between Voltage (Potential
difference), Current and Power
Power = Volts x Amps
W=VxA
Recall the relationship between Voltage (Potential
difference), Current and Resistance
Volts = Amps x Resistance
V=IxR
Batteries
Polarity can be important
Direct Current / Alternating Current (DC / AC)
AC easier to generate and change voltage
Frequency
mains supply
50Hz (230 volts)
normal hearing
100Hz - 15kHz
audio communication
300Hz - 3kHz
HF
3MHz – 30MHz
VHF
30MHz – 300MHz
UHF
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
Modulator
1
2
Audio
Stage
4
RF power
amplifier
3
Frequency
Generator
Need to remember
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
audio (or data) signal is modulated on to the radio frequency
“carrier” in the modulation stage of the transmitter
FM
AM
Common modulation modes :Voice
AM
Carrier and two side bands
SSB
Single side band
FM
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
The Receiver
Loudspeaker
Detection
1
Tuning and rf
amplifier
2
3
Audio
amplifier
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.
¼λ
¼λ
½ wave dipole
Some more antennas
λ/4 ground
plane
5/8 λ
Yagi
Polarisation ?
Radiation pattern ?
Long Wire
Effective Radiated Power (“erp”)
10W
Gain 10 dB
100W
= erp
Gain in dB = 10Log10 (Power Out)
(Power In)
3 dB = 2 times
6 dB = 4 times
10 dB = 10 times
9 dB = 8 times
Points on Antennas
If an antenna is not correctly designed for the
frequency it will not match the transmitter and will not
work effectively
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
¼λ
¼λ
Balanced and unbalanced
¼λ
¼λ
Balun
Standing Wave Ratio
i
¼λ
v
¼λ
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).
SWR v Frequency for a dipole 20.22m in length
6
7
8
SWR
A high SWR (measured at the transmitter) is an
indication of a fault in the antenna or feeder (and not the
transmitter
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
400 Km
70 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
Ionosphere basics
400 Km
70 Km
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.
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
EMC
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.
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
Alpha
Bravo
Charlie
Delta
Echo
Foxtrot
Golf
Hotel
India
Juliet
Kilo
Lima
Mike
November
Oscar
Papa
Quebec
Romeo
Sierra
Tango
Uniform
Victor
Whiskey
Xray
Yankee
Zulu
Repeaters
GB3GF
Output Frequency
433.300 MHz
Input Frequency
434.900 MHz
Access
1750Hz initial access