1MM6ABC is a callsign transmitted from Scotland. it is first MM that makes it Scotland
/A is the suffix used to transmit from a friend
2the ALC line between the transmitter and the external power amplifier is to provide a signal from the the PA to limit or reduce transmitter output power
frequency synthetsiser may produce the wrong output if the signals into the phase comparator are on different frequencies
3the relative permittivity of a dielectric is a measure of the change in capacitance compared to a capacitor if the same dimensions in a vaccum
in the case of self inductance, the magnetic field created by a changing current induces a voltage in the same circuit
4on applying a constant voltage, V, to a resistor-capacitor series combination the current falls from an initial value equal to V/R towards 0.
a transformer cannot produce a greater power output in the secondary winding than the power fed into the primary winding
5the modulation index of an RF signal is the ratio of the frequency deviation from the nominal carrier frequency to the frequency of the audio signal it i
it is often found that adding a preamplifier to an HF receiver has little effect on the signal to noise ratio of weak signals because natural HF noise is relatively high making it easy to produce receiver front ends with much lower internal noise
6a transceiver will often share circuits between transmitter and receiver this would include IF filters
when travelling away from a transmitter on clear ground, it is noted that the field strength is halved. the power flux density fan be expected to have reduced to a quarter of it's initial value
7Galactic noise is most likely influence reception when operating EME
a neighbour has a new television of good quality installed in his lounge. there are instances of interference from nearby amateur and CB transmissions. it would be sensible to check the aerial and it's downlead may have deteriorated since they were installed
8one probable cause of mains borne interference is an antenna which positioned too close to an overhead power supply cable
it is difficult to achieve a good RF ground when the transmitter is in an upstairs room of a house or building because the distance the actual ground is a substantial portion of a wavelength so impedence transformation needs to be considered
9you are operating from a rare and slight after location but are swamped by requests for a contact such that you cannot identify any incoming callsigns and your replies are simarily swamped. to fix this you reply saying you're are listening a few khz away
if working on live equipment you should be isolated from earth by a rubber mat or insulation
10the purpose of resistors which have different resistors is to provide DC voltages ranges
to measure the RF output power of a transmitter, the power should be set to the highest power range to begin with
11you may pass messages to a non amateur if it's related to an international disaster
the peak transmit power above which an EMF assessment must be carried out is 100W e.i.r.p
12in a mains power supply unit the purpose of the reservoir capacitor is to smooth DC pulses
the RF output power of a transmitter is always less than the DC input power
13AF gain control setting on the receiver will not affect the strength of an HF signal shown on a S meter
the volume from the loudspeaker of a radio receiver remains fairly constant even when the receiver is tuned between strong and weak signals because of the automatic gain control
14a number of ferrite rings threaded over a length of coaxial cable could act as a balun
the capacitor in the trap of a trapped dipole antenna has become disconnected, this will then cause difficulty in achieving a match in the higher of the two designed frequencies
15an antenna matching unit can be used between the transmitter and feeder to allow a suitable load to be presented to the transmitter, so that one antenna can be used on several bands
an amateur transmitter can cause stronger RF fields than electronic equipment can tolerate if interference occurs then you must limit the transmitter power to below the maximum value specified in the licence
16in an international disaster you're allowed to pass messages onto an international station on behalf of a non amateur
if the transmitter is capable of unattended digital operations then it is not in use for unattended use for amateurs
17An SSB receiver is picking up a signal about 4kHz away from the signal to which it is tuned. This is an indication of
poor selectivity in the receiver
In a crowded band there are several radio signals all closely spaced in frequency. To select the wanted signal a superhet receiver uses tuned circuits in the IF amplifier.
18The beam width of a Yagi antenna is the angle between the half power points of the radiated RF
the most likely cause of VHF multipath propagation is reflection off a building
19The immunity of a domestic music system to amateur transmissions can be improved by filtering on the mains supply lead
20MU7XYZ is from a full license
you must confirm licence details every 5 years
21an audio signal which is fed to an amplitude modulator results in new frequencies caller sidebands
an amplitude modulated signal consists of two sidebands and a carrier
22VFO makes it easy to change frequency but may lack stability
the output of a VFO depends on the values of L and C in a resonant circuit
23a balanced modulator produces a double sideband with the carrier suppressed
the narrowest possible bandwidth can be achieved through a high Q factor and a low resonant frequency
24IF amplifier provides the most gain and selectivity in the radio receiver
the demodulator stage is where the signal used to produce the AGC feedback to the IF amplifier is obtained from
25a HF horizontal antenna is the least likely to cause interference problems
when fitting an RF earth it may also be helpful to fit a ferrite ring on the mains lead.
26MUF is the highest frequency that is available over a particular path
Most HF propagation occurs by F layer refraction
27Fading is caused by signals travelling by slightly different parallel paths arriving with different phases
D layer of the ionosphere is at a height of 120,km and tends to enhance ionospheric propagation
28Sporadic E is a refraction of VHF signals by highly ionised patches in the E layer.
Sporadic E can refract VHF and uHF signals back to the earth's surface
29Try to improve the immunity of the affected receiver by filtering the mains leads
an amateur radio transmitter might cause RF fields stronger than the agreed limits on electromagnetic disturbances
30mechanical thermostat can cause a heavy interference with a rasping sound
the purpose of a filter in the power supply leads to a transceiver is to minimise the level of RF from the transmitter getting into the mains wiring
31placing a ferrite ring round an RF feeder will reduce the common mode currents because the magnetic field from each conductor adds together
the best way to check for spurious signals and harmonics is to use a general coverage receiver
32using a loft antenna for amateur radio activities is likely to cause considerable interference to tv reception
RF output from the transceiver should be connected to a dummy load
33the reason why several ferrite rings fitted over a two wire ribbon feeder is found to be ineffective is because the transmitted signal is a differential mode signal and is not affected by ferrite
on installing amateur radio in a vehicle is a available from the federation of communication services code of practice
34Polyethene is a good conductor of audio frequencies but lossy at RF
if it is a capacitor leading then it would have the current leading and the voltage lagging in relation to time period
35R.F.C has to provide DC power to the transistor and has to limit the RF signal getting back to the supply rail. it should have a high inductance to have a high HF reactance/impedence
impedence ratio is the square of the turns ratio.
36a high Q factor in AMU in tuned circuits can cause the circulating currents and voltages in the tuned circuits to be high
Class A biasing has the output signal in a complete smooth sinewave, larger than the input and 180 degrees out of phases with the input.
37in order for an oscillator to oscillate the gain in the amplifier stage must be at least equal to the loss in the feedback stage
SSB cannot use a nonlinear external RF power amplifier
38ALC line between the transmitter and external power amplifier provides a signal from the PA to limit or reduce the transmitter output power
overmodulation is most likely to cause interference caused by harmonics of the audio signal
39in a single sideband transmission the bandwidth is half that of the amplitude modulation
a VFO makes it easy to change frequency but may lack stability compared to a crystal oscillator
40peak level at which the EMF is restrictions in the amateur licence apply assuming the average level is not breached is 100W EIRP
the intermediate licence permits the unattended operation of a beacon for any purpose including direction finding and propagation
41an advantage of using a synthetsiser as the oscillator in a transmitter is it is tuneable and has the frequency stability of a crystal
double sidband signal with the carrier suppressed by the balanced modulator
42a harmonic of your transmission is quite likely to be heard by other amateurs in a different amateur band
the signal used to produce the AGC feedback to the IF amplifier is obtained from the demodulator stage
43unattended digital communications are permitted by the licence provided operation is consistent with the terms of licence
remote control facility available to full licencees and not available to lower classes is to use an internet link to access the main station
44inductors in parallel have a total inductance less than the smallest one
high permeability means high magnetic effect
45the purpose of operating split frequency is that it spreads out stations calling in a pile up allowing some callsigns to be copied
smallest capacitor in series will have the largest charge
46a member of the salvation army is a member of the user service
operating in a cept country under the terms of the UK amateur licence is not available to intermediate licences and below
47In Scotland # is replaced by M. At the end /M is added for mobile. At the end /MM is added for at mobile at seas.
not being able to to receive on a frequency you are receive on a frequency you are transmitting on is a breach of your licence
48full licensees may use any power up to 400W on the remote control link,
you must have written permission of the ships masters to transmit on his ship
49capacitors in parallel add to each for capacitance and it is less than the smallest one in series
inductors in series are added together
50the danger associated with low voltage but high current is very hot metal
before connecting your own RF earth to the mains safety earth you must consult a competent electrician
51the reactance of a capacitor falls as frequency rises
the small residual error from digital sampling is called quantisation distortion in which it picks the nearest digital value or quantity.
52Full licences have MW at the front of their callsign
operating from a vessel at sea is only allowed at full licence
53use the callsign of the superviser
if a non amateur walks into room while you're transmitting continue speaking as normal
54secret code on air is only permitted under specific circumstances
you should check your radio equipment is not causing undue interference from time to time
55ladders should be 4:1 length
when using a ladder ensure one side is connected by a safety rope
56a significant feature of vehicles batteries is that they contain corrosive acids
fingers are kept behind the blade is most important when using tools
57Only an intermediate licencee can design build and use to transmit from their own equipment
When changing from CW to FM give your callsign in first over
58As a foundation licensee you can only supervise that person if they hold a UK amateur licence
At foundation level you're not allowed to transmit directions to a radio club event to anybody who is listening
59When joining a net of other amateurs you must establish contact with any one amateur already in the net by exchanging callsigns
Foundation licence only permits use in the UK
60EMF restrictions in the amateur licence apply at power levels above 10W EIRP
When completing an EMF check upload your results to Ofcom
61When using someone else's radio equipment operate under their conditions of the radio licence.
The radio equipment being used is the callsign is given in the identification of the station
62during a disaster in another country you may only hear non amateur stations on amateur bands
Raynet UK is not a user service
63You may pass messages or allow User Service to use your equipment during an emergency
you have to avoid undue interference to any wireless telegraphy
64if interference occurs to a neighbors tv you will be required to reduce emissions satisfactory to Ofcom
intermediate licence permits unattended operation of a beacon for any purpose including finding and propagation
65when using a radio link to remotely control the main transmitter, the link equipment is limited to a transmit power of 500mW pep e.r.p
link to a remote transmitter must be failsafe
66intermediate licencee may operate in France only with the permission of the French authorities
schedule of the amateur licence shoes the frequency bands allocated for amateur use within the UK
67when giving your location the method to give is the IARU locator in the format AB12xy
Only a club member who has the club licence holders permission can supervise at a club station
68a recognised training course is a course if successfully completed result in a radio amateur examination examination pass certificate
a person with an amateur licence from another country can operate using the callsign of a UK under the supervision of any UK amateur with a current licence
69the need to avoid sending menacing messages by amateur radio the wireless telegraphy regulations 1988
you may only communicate on a frequency that is in the UK licence schedule
70if you have to retransmit a message you have to ensure to retransmit the originators callsign, the origin of the message and retransmission are clear
emissions from your transmitter should be not more than 1% of the mean power falls outside the nominal modulated carrier bandwidth
71radio link in an amateurband user for remote control of the main transceiver must be compliant with schedule 1 of the licence
when operating on a vessel at sea the master of the vessel can require to close down on demand and keep a log of your transmission
72when operating from a vessel at sea near Australia the allowable frequency bands are those which are in both the UK and ITU region 3 amateur schedules
when operating on 5.334MHz USB voice it is necessary to identify your station when leaving the net
73Only those with an amateur licence are permitted to be inside the EMF exclusion zone
A filament bulb works in either direction of the current as long as the connection is made
74Audio range of frequencies is 300Hz-3kHz
HF range is 3MHz-30MHz
75a reversible chemical process is a feature of a secondary cell
a resistor marked with 27Ohms 5% means that it's resistance is 5% within 27ohms
76decreasing the area of the plates of a capacitor will increase its ability to store a charge
3 capacitors of different values connected in series have an effective capacitance smaller than the smallest capacitor
77a magnet waved over a piece of copper will result in a voltage being induced
inductor relies on that when a current passes through a wire a magnetic field is formed
78a single coil is an inductor and 2 coils sharing a magnetic field is a transformer
inductors in series increases total inductance, in parallel the inductance is reduced. All in parallel will have lowest inductance
79capacitors can pass alternating current because the capacitor charges and discharged in alternating directions
V/I in an inductor and capacitor is reactance
80resonant frequency containing a capacitor and inductor depends on the values of the capacitor and inductor
a voltage across a reverse based diode will have the maximum voltage as current cannot pass
81transistor amplifiers feature is that a small change in base current can cause a large change in collector current
transistor used as an switch must have an input signal greater than that required for an amplifier
82biasing a transistor is supplying the correct DC voltages and currents
the function of the transistor in an oscillator is to maintain the oscillations in the tuned circuit
83battery gives it's capacitance in ampere hours
the one with 4 diodes in a square is called a bridge rectifier
84a way to rectify using a diode in AC transformer so that there is no outputting the negative half cycles is to use a capacitor
a switch mode power when compared to a linear power supply of the same output is light, no heatsink needed and quite efficient
85Electromagnetic waves field strength falls linearly with distance
circular polarization is to have the electric and magnetic fields remaining at right angles but rotating through one revolution per wavelength
86when there is a high sunspot count it is likely that HF propagation will be noticeably enhanced allowing many more contacts
the highest MUFs can be expected to occur during the day in the winter
87in ascending order of frequencies: LUF, critical frequency, optimum working frequency, MUF
NVIS has difficulties with finding suitable frequencies above the LUF and below the MUF
88The polarisation of an HF antenna, particularly for receiving does not matter as the plane of the wave may be changed in the ionosphere
EME contacts are best made when the moon is perigee (closest) because the moon is a poor RF reflector.
89auroral flutter on radio signals is caused by movement of ionised curtains
the purpose of a link budget is to check that the proposed system will deliver an adequate signal to noise ratio
90An electric drill can cause interference because of sparking at the commuter and thus can RF interference over a limited distance
SSB has amplitude variations which can be demodulated to an audio signal which maybe recognisable and if it has the most power it would cause the most interference
91the purpose of a dummy load is to prevent unwanted radiation escaping back down the power leads
3 requirements of a dummy load are: correct resistance, no reactance, no RF radiation
92in general houses are more susceptible to picking uo verticle signal so horizontal signals are better. The further the house is the least likely an interference is going to be caused
electromagnetic compatibility is when electronic equipment must be reasonably immune to electromagnetic disturbances and must not cause intolerable disturbances
93If RF is not being sent down by power lines from an amateur transmitter and radiated field strength is acceptable then one way to fix transmission is to improve the immunity of the affected receiver by filtering main leads
amateur radio transmitter might cause RF fields stronger than the agreed limits on electromagnetic disturbance
94older or poorly installed equipment might not meet the standards of the European EMC immunity requirements
a digital TV suffering from modest interference from an FM amateur transmission will cause a jerky picture and jigsaw like pixelation
95FM speech transmission if picked up by a music system even if it's radio is off can cause the music being played being distorted or reduced in volume
SSB speech transmission if picked up by a music system even if it's radio is off can cause interference which creates speech like sounds
96if a domestic radio is found to be susceptible to interference from an amateur transmission, even if ferrite rings have no effect on the receiver then it is suffering from a direct pick up
a known problem with masthead tv amplifiers is that they amplify a wide range of frequencies
97the purpose of a filter in the power suppy leads to a transceiver is to minimise the level of RF from the transmitter getting into the mains wiring
HF and VHF transmissions cause interference to a TV set a way to cure this is to fit a high pass filter in the TV aerial down lead.
98Poor installation of EMC compliant equipment is quite likely to compromise it's safe and effective operation
when you modify a commercial transceiver to operate in an amateur band it must comply your amateur radio licence
99SSB is most likely to be a cause of cross modulation
masthead amplifiers cover from 50Mhz or 90Mhz up to around 900Mhz. 2m and 70cm are within that range
100the wanted signal, transmit or receive, coax or twin wire is always in differential mode.
if RF is being picked up on a loudspeaker leads of a music system and speech is heard the most likely effective cure is to put ferrite rings at the amplifier ends of the leads.
101if the RF earth on an HF transmitter is missing or not well installed then. the transceiver will be hot to touch
minimum coupling between HF diploe antenna and the feeder is achieved by keeping the diploe elements and the feeder at right angles to each other
102one should ask if the frequency is in use because you could interfere with someone listening to a more distant station
the purpose of a much longer cq call on HF SSB is to allow people tuning round to tune correctly on to your transmission
103to reduce the risk of an amateur on a hilltop transmitting into two repeaters at the same time, the repeaters are on the same radio frequency but different sub audio tones
it is necessary to have different transmit and receive frequencies to prevent the repeater transmission causing interference to it's own frequency
104when connecting a computer sound card to the microphone socket of your radio you should check the audio level is correct and correct ptt operation
signal report 5 and 2 means weak signal but still very clear to read. signal report range from 1-9, readability is out 5.
105if you're trying to access a digital voice repeater, one reason it might not work is that your digital transceiver is using a different protocol
when borrowing a friend's digital voice handheld radio one must check that any embedded callsign is reset to your callsign
106despite normally accessing the local DV repeater easily and recieving a good signal from it, there are occasions where it is quiet but you have difficulty accessing it this is because another user is accessing it on analogue FM
the Q code for fading is QSB
107your data transmissions sound distorted and decoding is poor this maybe due to the excessive audio into the microphone socket.
operation through a satellite will require two receivers to cover both uplink and downlink bands
108transmitting a strong signal to an amateur satellite is likely to result in an unfair share of the downlink transmit power
when hearing a station call CQ and clearly getting frequent replies but your replies are not getting an responsive while you have strong station and propagation is good this might occur because they might be operating split frequency
109twin open wire feeder both wires should carry the RF signal which should have equal but opposite signals on both conductors
the antenna will convert electrical signals into radio waves
110the feed point impedence of an antenna is depended on the dimensions of the antenna in relation to the signal wavelength
when connecting BNC plugs, the braid of the cable should be connected to the outer body of the plug at both ends of the cable
111when a feeder is correctly terminated, the ratio of the RF potential difference to the RF current at the feed point is determined by the relative dimensions of the conductors
a choke balun is used for minimising current on the outside of the coaxial braid
112to achieve longer distances using HF the radiated signal should have a low angle of radiation
the shortest RF element on a Yagi is the director
113a wire dipole antenna is fitted with 2 parallel tuned circuits in each half of the dipole. the purpose of this is to allow the dipole to resonate on 3 bands
a dipole with a tuned circuit trap fitted 5m from the centre in each arm of the dipole is because the trap is resonant at the higher frequencies cutting off the outer lengths of the dipole
114standing waves on a feeder are an indication that the transmitter will see a different impedence to the feeder
the purpose of a antenna matching unit is to change the impedence the feeder presents to the transmitter
115when adjusting the AMU the SWR on the feeder will remain constant despite the variations in setting of the AMU
to ensure the RF field only exists inside a coaxial cable it is necessary to ensure that the outer braid or screen is electrically continuous from the cable to the plug and to the socket
116the process of adding information to the radio signal in a transmitter is known as modulation
microphone amplifier and oscillator feeds single into the modulator
117the first point in a transmitter in which an AM signal can be found is the modulator
if the oscillator is set wrongly the transmission can be set on the wrong frequency
118microphone amplifier has to limit the frequencies passed to the modulator to those required for voice communication and set the correct audio signal amplitude
interference caused to other stations on frequencies above and below the one you are using might be caused by over modulation, due to setting the microphone gain too high
119the function of a radio receiver is to recover information sent using electromagnetic radiation
tuning is carried out in the first stage of a radio receiver
120the first important function carried out in software defines receiver is digitising the received signals
peak deviation of a frequency modulated transmission is the deviation chosen as the system design maximum
121digital modulation is the narrowest bandwidth that is successful at transmitting the required information
the output frequency of a variable frequency oscillator depends on the bias setting of the associated transistor
122to help recent a continuously tuneable transmitter from drifting off frequency it is advisable to rigidly construct the VFO and put it in its own screened box
the instructions to generate the waveform by direct digital synthesis are obtained from a lookup table held in memory within the device itself
123a doublesideband signal with the carrier suppressed is normally produced by a balanced modulator
fast edges on Morse transmission will make the transmitted signal much wider than necessary
124a disadvantage of the superhet the IF is tuneable over a wide range
the stage in a radio receiver which provides the most gain and selectivity is the IF amplifier
125the superheterodyne is a type of receiver architecture which allows multi band reception without having to use separated tuned circuits to select the signal each band
the signal to produce the AGC feedback to the IF amplifier is obtained from the demodulator stage
126being hit hard by a chuck key suggests It was left in the chuck of the drill
when operating mobile with antenna on the car roof, you must cease transmitting when stationary with pedestrians around
127high DC voltages are likely to be found in equipment utilising thermionic valves
when avoidably working on a live equipment you should keep one hand clear of the equipment and earthed objects at all times
128safe levels of RF exposure vary with frequency. the lowest level is about 28V/m.
fitting a proprietary spark gap and discharge tube to the feeder to an HF dipole antenna should avoid the need to disconnect the transceiver during a thunderstorm
129when operating a special event station in tented accommodation and using an extension cable to provide mains power, it is necessary to use a residual current protective device.
when fitting a transmitter in a vehicle, you should provide a facility for hands-free operation to avoid distraction
130an FM transmission is regarded as "narrow band" when the modulation index is equal to or less than unity
the most significant effect of drift in a transmitter is that transmission may occur outside an amateur band
131a data transmitter feeds binary data signal direct to the modulator of the transmitter, resulting in a 170Hz transmitted frequency shift between a data one and a data zero. Off air this type of modulation is indistinguishable from feeding the binary data to modern reducing two audio tones separated by 170Hz and feeding them to the microphone socket of an SSB transmitter.
you cannot use a nonlinear external RF power amplifier on SSB Modulation
132linearity is meant by a given percentage change in the input will result in exactly the same percentage change in the output
the ALC line between the transmitter and external power amplifier provides a signal from the PA to limit or reduce transmitter output power
133over modulation is most likely to cause interference caused by harmonics of the audio signal
overdriving an external power amplifier may cause intermodulation products because the PA will be operated outside it's linear range
134if the drive to the power amplifier stage of a transmitter is a bit too high, the most likely is an increase in the bandwidth of the transmitted signal
a transmitter is designed to perform all its modulation functions at 5Mhz and mix the modulated signal with a signal from a synthetsiser which can be multiplied up as required. the filter required is band pass filter
135a frequency synthetsiser may produce the wrong output if the signals into the phase comparator are on different frequencies
listening close to the top of 7MHz band it is noticed that weak singals become easier to resolve in the late afternoon when a broadcast station on 7.22Mhz ceases transmission. it is well over 30khz away so it was not expected to be a problem with a 2.7kHz SSB filter on the wanted signal. the likely cause is intermodulation products in the receiver front end
136a wideband scanner picks up a good CW signal when turned to 3.61Mhz but picks up the same signal when tuned to 7.51Mhz. A reason for this might be refugee intermediate frequency is 1.95Mhz.
the factor suggesting a low intermediate frequency should be used in a refugee design is that the rejection of adjacent channel interference is easier to accomplish
137a feature of an over coupled response in an IF transfotmer is that the -3db bandwidth is wider than other coupling methods with minimal effect on the response at -30 or -60db
an operator has taken care to get a really good IF filter for CW usebhut the results are much poorer than expected; a very clean stable signal appears to get through the filter over a wider frequency range than the filter response. the reason for this the receiver's local oscillator has a high level of phase noise close to its operating frequency
138demodulation of an FM singals is normally achieved by a circuit which uses changes in phase angle in a tuned circuit to give different volatages, which may then be rectified
the AGC is turned off when an all mode receiver is set to FM because the gain is maximiser so a limiter results in constant signals
139choose a slow decay on the AGC means that the background noise, particularly when on SSB will rectify to its normal level over a few seconds rather than instant
the method in which a software defined receiver uses to modulate any incoming singal is that the the receiver demodulates the amplitude of the signal in 2 phases separated by 90 degrees allowing any modulation mode to be extracted
140automatic level control is used in boths parts of receiving and transmitting from a transceiver
apart from capacitance, another parameter to be considered when selecting a low value capacitor is breakdown voltage.
141an oldstyle doorbell has a coil acting as an electromagnet pulling an iron arm across to strike the gong, but in doing so breaks the circuit so the arm returns to the rest position to repeat the process. in breaking the circuit the current stops quickly
if voltage is leading the current in a graph against time then the chart is for a capacitor
142the purpose of the inductor marked RFC in the circuit is to help minimise RF signals on the positive supply rail
to avoid alliasess appearing in the digital representation of an analogue signal it is normal to use an analogue filter to remove signals at frequencies above half the sampling rate
143the Fourier transform is used to take the digital samples in the time domain and calculate the amplitudes of the signals in the frequency domain
in a transformer the energy is transferred from the primary to the secondary by mutual inductance
144when selecting a core for an intermediate frequency transformer you should consider the frequency range over which it will operate
a home made crystal oscillator is found to be unstable in frequency and adjustment of the small trimmer capacitor can cause it stop oscillating. the circuit is published in a reputable magazine and is known to work. the next reasonable is to check the stability and adequacy of the bench power supply unit
145some ATU can have tuned circuits with a high Q factor. A significant implication of this is that the circulating currents and voltages in the tuned circuits can be very high
a circuit which posses dynamic resistance is the effective resistance of a parallel tuned circuit at resonance
146a zener diode is reverse biased to provide a specified reference voltage
a transistor amplifier had a current gain of 1 and a voltage of about 30. The configuration of the device is common base
147a sine wave signal is supplied to the base of a common emitter amplifier which is biased in class A has the output in a complete smooth sinewave, larger than the input and 180 degree out of phase with the input
a transistor amplifier exhibits a high current gain but a voltage gain of about 1 is a common collector
148an amplifier operated in class c is particularly suited to radio frequencies for CW and FM
class A of biasing is the least likely to cause the production of harmonics of the input signal
149unwanted radiation from a local oscillator stage in a receiver can be minimised by using a thin metal cover round the oscillator
soldering a wire to the copper track of a circuit board will melt another metal onto the wire and the copper board
150the purpose of flux is to prevent the copper surfaces oxidising as they get hot
aluminium cannot be soldered using a tin or tin/leas based solder
151linear power supply compared to switched mode supply of the same output is heavy and has large heatsinks
the modulation which has the same input, in which has twice the bandwidth or the other is SSB and AM
152chirp is an effect often associated with poor voltage regulation of the oscillator
if the RF amplifier at the receiver input has a high level of electrical noise then it will affect the receiver's sensitivity
153the reason the superhet architecture was developed from the tuned radio frequency (TRF) was to overcome the difficulty in producing narrow RF filters at higher radio frequencies
if an antenna was used on a frequency other than that for which it was designed for the impedence seen by the transmitter will not be the characteristic impedence of the feeder
154the mechanism that limits the range of a ground wave signal is the energy in the signal is absorbed into the ground
the sunspot cycle affects the degree of ionisation of the ionosphere which affects the HF skywave propagation. it is a 11 year cycle
155the amateur band plans state that SSB should not be used on 30m.
if the mains wiring is carrying sufficient RF signal to cause interference to other equipment then the logical next step is to fit a filter to mains lead to the transmitter
156a "slow blow" fuse is useful as some devices take a surge of current but still need good overload protection
when operating at a transmit power of 50W you should be aware that the EMF compliance distance is several distance from the antenna
157when identifying your station you should use the same type of transmission as used for transmission
when another amateurs is using your radio and is identifying using your callsign then you must supervise them because they are using your callsign
158human speech is 300-3000Hz which is the range required for amateur radio speech communication purposes
the bottom of the ionosphere is at a height of 70km
159the frequency which is least likely to cause interference is frequency modulation
if a group of amateurs is playing music then you should call into the group and object to playing music
160gain of beta of a transistor is the ratio of collector current to base current
if a PME mains supply suffers a break in the neutral conductor somewhere on the street outside the premise the risk this can cause is that the mains earth and bonded mentalwork will rise significantly above earth potential
161voltmeters needs a series resistor to handle the larger currents so it can measure the voltage
if the inductor has a temperature coefficient of +3ppm per degree C. The temperature coefficient needed for the capacitor to keep the centr frequency as stable as possible is 3ppm.
162a sine wave signal needs both amplitude and frequency to make it identifiable
peak voltage = RMS voltage * √2
163capacitors reactance falls as frequency increases
as an inductor frequency increases the reactance increases
164if swr is reading higher than normal then there is a fault in the feeder or antenna
an AMU can correct a mismatch in power between the transmitter and feeder
165a rectangular waveguide should have the longest side greater than half a wavelength at the frequency of operation
a waveguide should be used in the gigahertz range
166choke balun is used for minimising current on the outside of coaxial braid
the gain from an isotropic to a normal dipole is a gain of 2.15dbi
167standing waves on a feeder are an indication that the transmitter will see a different impedence to that of the feeder
return loss at transceiver = return loss at antenna + 2 * line loss
168a well matched antenna will exhibit a high return loss and low SWR
Logs should be kept in UTC because all communications stations worldwide use UTC to avoid the confusion
169on a busy repeater the speakers voice is sometimes overlaid with series of beeps, this is because the speaker didn't wait for a reset tone after the previous speaker
if you're trying without success to access a digital voice repeater while on holiday in the UK , a reason for this is that the digital transceiver is using a different protocol
170when taking part in a competition such as a VHF field day, you give your call sign and serial number of the contact
if the data transmissions sound distorted and decoding is poor this could be because there is excessive audio in the microphone socket
171if an activity prodocues swarf then you need to wear eye protection
the main hazard using ladders when hkusesbhave overhead mains supply is the risk of electric shock from coming into contact with the cables
172elevated wires and feeders should be suitably positioned and fixed
being hit hard by a chuck key suggests it was left in the chuck of the drill
173when using a pillar mounted drill the drill is secure and unlikely to wander
some protection from static charge collected on antennae can be obtained by a high value resistor connected between the antenna and earth
174high DC voltages are likely to be found in equipment utiling thermionic valves
using PME practice, the supply company will have connected the premises main earth point to the neutral conductor at the point of entry to the premises