Peter

Those who wonder about self-build or believe that the very simple Amateur test and very basic
test equipment make them an electronics expert, chew on this for a while...

(Some of the spec and methods are very long, so parts have been selected to
show what kind of knowledge and equipment will be required. These are
marked with ** and the comment on editing).


5.1.5 Type of modulation
Only angle modulation with appropriate pre-emphasis and de-emphasis
shall be used.


TRANSMITTER:

FREQUENCY ERROR
The frequency error shall not exceed ± 0.6 kHz.

** This must be tested on an artificial antenna under normal and
extreme conditions, which are described after the specifications **

CARRIER POWER
Both the transmitter carrier power, and the effective radiated power of an equipment
with an integral antenna, shall not exceed 4 watts.
The equipment shall be constructed in such a way that an increase of output
power cannot easily be achieved by actions undertaken by the user of the
equipment.

** This must be tested on an artificial antenna under normal conditions**

FREQUENCY DEVIATION
The maximum permissible frequency deviation shall be ± 2 kHz.

Method of measurement
The frequency deviation shall be measured at the output of the transmitter
connected via a 50 ohm power attenuator, to a deviation meter capable of
measuring the maximum deviation, including that due to any harmonics
and intermodulation products which may be generated in the transmitter.

The modulation frequency of the test signal shall be varied between the
lowest frequency considered to be appropriate, and 10 kHz. The level
of this test signal shall be 20 dB above the level required to give a
frequency deviation of 1.2 kHz at an audio frequency of 1250 Hz.

UNWANTED AMPLITUDE MODULATION
For the measurement method see clause 8.4.1. The maximum permitted unwanted
amplitude modulation shall not exceed 5%.

Method of measurement
The amplitude modulation shall be measured at the output of the transmitter
connected via a 50 ohm power attenuator to an amplitude modulation meter
capable of measuring the maximum amplitude modulation including that due
to any harmonics and intermodulation products which may be generated in the
transmitter. The modulation frequency of the test signal shall be varied between
the lowest frequency considered appropriate, and 10 kHz. The level of this test
signal shall be 20 dB above the level required to give a frequency deviation of
1.2 kHz at an audio frequency of 1250 Hz.

ADJACENT CHANNEL POWER
For the definition and measuring method see clause 8.5. The adjacent channel
power shall not exceed a value of 20 microwatts


** The exact method of measurement is rather long, so sections have been selected**

Method of measurement
The adjacent channel power shall be measured with a power measuring receiver
which conforms with the requirements given in Annex D referred to in this clause
as the "receiver".

a) The transmitter shall be operated at the carrier power measured in clause 8.2
under normal test conditions. The output of the transmitter shall be linked to
the input of the "receiver" by a connecting device such that the impedance
presented to the transmitter is 50 ohms and the level at the "receiver" input is
appropriate. For equipment with an integral antenna the connecting device is a
test fixture as described in clause 7.6;

b) With the transmitter unmodulated, the tuning of the "receiver" shall be adjusted
so that a maximum response is obtained. This is the 0 dB reference point. The
"receiver" variable attenuator setting and the reading of the rms value indicator
shall be recorded.

c) The tuning of the "receiver" shall be adjusted away from the carrier so that
the "receiver" -6 dB response nearest to the transmitter carrier frequency is located
at a displacement of 5.75 kHz from the nominal carrier frequency.

d) The transmitter shall be modulated by a test signal of 1250 Hz at a level which
is 20 dB higher than that required to produce a deviation of ± 1.2 kHz.

e) The "receiver" variable attenuator shall be adjusted to obtain the same reading
as in step b) or a known relation to it.

g) The measurement shall be repeated with the "receiver" tuned to the other
side of the carrier.

h) If the equipment has a microphone socket the measurement shall be
repeated with an input of 1.5 volt at 1250 Hz at this socket.

SPURIOUS EMISSIONS OF THE TRANSMITTER
In the frequency bands in Table 2 the power of conducted and radiated spurious
emissions shall not exceed 4 nanowatts for the transmitter operating and 2
nanowatts for the transmitter in the stand-by condition.

Table 2
47 MHz to 69 MHz
87.5 MHz to 118 MHz
174 MHz to 230 MHz
470 MHz to 862 MHz

The power of any spurious emissions at any other frequency outside the above
bands shall not exceed the limits in Table 3 and Table 4.

Table 3: Conducted Emissions Limits
Frequency Range 9 kHz to 1 GHz above 1 GHz to 2 GHz
Tx operating 0.25 microwatt (-36 dBm) 1 microwatt (-30 dBm)
Tx stand-by 2 nanowatts (-57 dBm) 20 nanowatts (-47 dBm)


Table 4: Radiated Emissions Limits
Frequency Range 25 MHz to 1 GHz above 1 GHz to 2 GHz
Tx operating 0.25 microwatt (-36 dBm) 1 microwatt (-30 dBm)
Tx stand-by 2 nanowatts (-57 dBm) 20 nanowatts (-47 dBm)

In the case of radiated measurements for handportable stations the
following conditions apply:
internal integral antenna: the normal antenna shall be connected
external antenna socket: an artificial load shall be connected to the
socket for the test.

** The emissions must be measured and logged at all frequencies between
9KHz and 2GHz, while connected to a 50 Ohm power attenuator.
This is repeated on stand-by, to check receiver emissions **

** Extratest equipment is needed for hand-held testing. **

TRANSIENT FREQUENCY BEHAVIOUR OF THE TRANSMITTER
The transient periods are given in Table 5. A graph of the transient periods
for the case of equipment operating in the frequency range above 300 MHz to
500 MHz is shown in Figure 3 as an example.

Table 5: Transient Periods
t1 5.0 ms
t2 20.0 ms
t3 5.0 ms

During the periods t1 and t3 the frequency difference shall not exceed the value
of 1 channel separation.
During the period t2 the frequency difference shall not exceed the value of half
a channel separation.
In the case of handportable stations, the frequency deviation during t1 and t3
may be greater than one channel. The corresponding plot of frequency versus
time during t1 and t3 shall be recorded in the test report.

This measurement applies only to equipment with an external antenna connector.


** The method gives a setup diagram, defining what equipment must be used
and how it is to be connected
The method is long, defining exact frequencies, levels, etc. **

SYNTHESISERS AND PHASE LOCKED LOOP (PLL) SYSTEMS
If - for determining the transmitter frequency - use is made of a synthesiser
and/or a PLL system, the transmitter shall be inhibited when synchronisation
is absent.

==
Receiver parameter limits

MAXIMUM RECEIVER SENSITIVITY
The maximum usable sensitivity shall not exceed an e.m.f. of 6 dBµV. This
requirement only applies to equipment with an external antenna connector.


Method of measuring the SND/ND ratio
The test signal, at the nominal frequency of the receiver, with normal test
modulation, clause 7.4, at an e.m.f. of 6 dBµV, value of the limit for the maximum
usable sensitivity, shall be applied to the receiver input connector. An audio
frequency output load, a SINAD meter and a psophometric telephone weighting
network as mentioned in clause 9.1.1, shall be connected to the receiver output
terminals. Where possible, the receiver volume control shall be adjusted to give
at least 50% of the rate output power, clause 7.3 or, in the case of stepped volume
controls, to the first step that provides an output power of at least 50% of the rated
output power.

The test signal input level shall be reduced until a SND/ND ratio of 20 dB is obtained.
The test signal input level under these conditions is the value of the maximum usable
sensitivity. The measurement shall be made only under normal test conditions.

ADJACENT CHANNEL SELECTIVITY
The adjacent channel selectivity shall not be less than of 60 dB. This requirement
only applies to equipment with an external antenna connector.

Method of measurement
The two input signals shall be connected to the receiver via a combining network.

The wanted test signal, at the nominal frequency of the receiver, with normal test
modulation, clause 7.4, at an e.m.f. of 6 dBµV, value of the limit for the maximum
usable sensitivity, shall be applied to the receiver input connector via one input of
the combining network.

The unwanted test signal, at a frequency of 10 kHz above the nominal frequency
of the receiver, modulated with a frequency of 400 Hz at a deviation of ± 1.2 kHz shall
be applied to the receiver input connector via the second input of the combining network.

The amplitude of the unwanted test signal shall be adjusted until the SND/ND ratio,
psophometrically weighted, at the output of the receiver is reduced to 14 dB.
The measure of the adjacent channel selectivity is the ratio in dB of the level of
the unwanted test signal to the level of the wanted test signal at the receiver input
for which the specified reduction in SND/ND ratio occurs. This ratio shall be noted.

The measurement shall be repeated with an unwanted signal at the frequency of the
channel below that of the wanted signal.

INTERMODULATION RESPONSE REJECTION
For the definition and measurement method see clause 9.3. The intermodulation
response rejection ratio shall not be less than 54 dB. This requirement only
applies to equipment with an external antenna connector.


Method of measurement
Three input signals shall be connected to the receiver via a combining network.

The wanted test signal (A), at the nominal frequency of the receiver, with normal
test modulation, clause 7.4, at an e.m.f. of 6 dBµV, value of the limit for the maximum
usable sensitivity, shall be applied to the receiver input connector via one input of the
combining network.

The unwanted test signal (B), at the frequency 20 kHz above the nominal frequency of
the receiver, without modulation, shall be applied to the receiver input connector via the
second input of the combining network.

The unwanted test signal (C), at the frequency 40 kHz above the nominal frequency of
the receiver, modulated with a frequency of 400 Hz at a deviation of ±1.2 kHz shall be
applied to the receiver input connector via the third input of the combining network.

The amplitude of the unwanted test signals (B) and (C) shall be maintained equal
and adjusted until the SND/ND ratio, psophometrically weighted, at the output of
the receiver is reduced to 14 dB.

The measurement shall be repeated with the unwanted signal from signal
generator (B) at a frequency 40 kHz above the wanted signal and with the
unwanted signal from signal generator (C) at a frequency 80 kHz above the
wanted signal.

The two sets of measurements described above shall be repeated with the
unwanted signals below the nominal frequency of the receiver by the specified amounts.

SPURIOUS RADIATIONS
The power of any spurious radiation shall not exceed the values in Table 6 and Table 7.

Table 6: Conducted Emissions Limits
Frequency Range 9 kHz to 1 GHz above 1 GHz to 2 GHz
Limit 2 nanowatts (-57 dBm) 20 nanowatts (-47 dBm)

Table 7: Radiated Emissions Limits
Frequency Range 25 MHz to 1 GHz above 1 GHz to 2 GHz
Limit 2 nanowatts (-57 dBm) 20 nanowatts (-47 dBm)




====

TEST CONDITIONS, POWER SOURCES AND AMBIENT TEMPERATURES

NORMAL TEMPERATURE AND HUMIDITY
The normal temperature and humidity conditions for tests shall be any convenient
combination of temperature and humidity within the following ranges:
temperature +15°C to +35°C
relative humidity 20% to 75%

When it is impracticable to carry out the tests under the conditions stated above, a
note to this effect, stating the actual temperature and relative humidity during the
tests, shall be added to the test report.

NORMAL MAINS VOLTAGE AND FREQUENCY
The normal test voltage for equipment to be connected to the mains shall be the
nominal mains voltage. For the purpose of these specifications, the nominal
voltage shall be the declared voltage or any of the declared voltages for which
the equipment was designed.

The frequency of the test power source corresponding to the AC mains shall
be between 49 and 51 Hz.

NORMAL REGULATED LEAD-ACID BATTERY POWER SOURCES ON VEHICLES
When the radio equipment is intended for operation from the usual types of
regulated lead-acid battery power source of vehicles, the normal test voltage
shall be 1.1 times the nominal voltage of the battery (6 volts, 12 volts etc.).

NORMAL OTHER POWER SOURCES
For operation from other power sources or types of battery (primary or secondary),
the normal test voltage shall be that declared by the equipment manufacturer.

EXTREME TEMPERATURES
For tests at extreme temperatures, measurements shall be made in accordance
with the procedures specified in clause 6.5, at the upper and lower temperatures
of -10°C and +55°C respectively.

Type approval test reports shall state which range is used.


Test procedure
Before measurements are made the equipment shall have reached thermal balance in
the test chamber. The equipment shall be switched off during the temperature stabilising
period. If the thermal balance is not checked by measurements, a temperature stabilising
period of at least one hour, or such period as may be decided by the testing authority, shall
be allowed. The sequence of measurements shall be chosen, and the humidity content in
the test chamber shall be controlled so that excessive condensation does not occur.
Before tests at the upper temperature the equipment shall be placed in the test chamber
and left until thermal balance is attained. The equipment shall then be switched on for one
minute in the transmit condition, followed by four minutes in the receive condition, after
which the equipment shall meet the specified requirements. For tests at the lower
temperatures the equipment shall be left in the test chamber until thermal balance is
attained, then switched to the standby or receive condition for one minute after which
the equipment shall meet the specified requirements.

EXTREME MAINS VOLTAGE
The extreme test voltage for equipment to be connected to an AC mains source
shall be the nominal voltage ±10%.

EXTREME REGULATED LEAD-ACID BATTERY POWER SOURCES ON VEHICLES
When the equipment is intended for operation from the usual types of regulated
lead-acid battery power sources of vehicles the extreme test voltages shall be 1.3
and 0.9 times the nominal voltage of the battery (6 volts, 12 volts etc.).

EXTREME POWER SOURCES USING OTHER TYPES OF BATTERY
The lower extreme test voltages for equipment with power sources using the
following batteries shall be:

for the Leclancé or the lithium type of battery: 0.85 times the nominal voltage
of the battery;
for the mercury or nickel-cadmium type of battery: 0.9 times the nominal
voltage of the battery.

No upper extreme test voltages apply.

EXTREME OTHER POWER SOURCES
For equipment using other power sources, or capable of being operated from
a variety of power sources, the extreme test voltages shall be those agreed
between the equipment manufacturer and the testing authority and shall be
recorded in the test report.

==================


As should be obvious from the above selections of specifications and required
methods, the CB specification requires rather more test equipment than Amateur
Radio does.
It is extremely unlikely that a radio Amateur will have the necessary equipment
and the knowledge to use it correctly.

Having the equipment is not the end of it, it must be regularly calibrated to ensure
that it is still accurate. The usual period is yearly, although some equipment is
calibrated more often.
This calibration must be traceable to national standards, and is not cheap.
It is not good enough to throw together a box of bits and call it test equipment, or
to buy some peice of test equipment and start using it - calibration is required.
Even new equipment may not come with a calibration certificate, that may be an
optional extra.

The days of someone setting up a small business in a Hertforshire village,
manufacturing CBs and selling the "DIY" kit version have long since gone.
For a bonus point, anyone want to name the company I am referring to and
the name of their CB radio that you could buy as a kit? Actually, the full
design was available in a magazine - I may still have that magazine
somewhere.


Regards,
Peter.
http://www.citizensband.radiouk.com/

--
Phhhrrrt... Beep.