RADIOMETER AFM2 Operating Instructions Manual

AFM2 MODULATION METER

,

1

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MODULATION

I

RADIOMETER

COPENHAGEN

n

:

BDE

0

U

I

This

instruction manual for the type in mind:

1)

On

page

AM distortion:

Carrier frequencies within

the range

Carrier frequencies within

the range 300

2) Signal-to-noise ratio for each stereo channel measured with a psophometer: Typically 66 dB at f40 kHz frequency deviation and RF

only when the level of the RF signal

AFM2S6 when the following specification changes and additions are borne

05

read

5

-

300 MHz:

-

1002 MHz:

is

valid for the Modulation Meter, type AFM2, but applies also

for

AFM2S6

0.3% distortion at 30% AM frequencies, within 20 Hz

1.5% distortion at 90% AM and at modulation

10

frequencies within

1.5% distortion at 30% AM and at modulation

frequencies within 10 Hz

<

200 MHz. These data apply

is

in the 30 - 100 mV range.

Hz - 50 kHz.

cmd

-

1~'kHz.

-.50 kHz.

'

at modulation

Furthermore, it applies to the Modulation Meter, type

06,

07,

D6,

E2,

corrections are made on pages

1

)

AF Output

2) AF Output Terminals

Nominally when meter reads 3/4 of ful I-scale deflection, e.g., at *75 kHz deviation in the deviation range.

3-pol e standard, type

and E4:

AFM2S4S5, when the following

0

dh (0.775

V

rms into 600R)

ZNA

333874/1

f

100

kHz

Table

of

Contents

SECTION A SECTION SECTION C SECTION D

1,

Description

2. Controls, Meters, and Terminals

SECTION 1, Connecting the Instrument

2, Measuring Ampl itude Modulation Percentage

3. Measuring Frequency Deviation

4,

Using a Crystal Oscillator

SECTION F - TECHNICAL DESCRIPTION F 1

-

INTRODUCTION

B - SPECIFICATIONS

-

ACCESSORIES

-

GENERAL DESCRIPTION

E

-

OPERATI NG l NSTRUCTIONS

Plurin

Unit, code 900-252

E

E E

E3 E4

1 1

1

1,

RF Input Circuit

2, Tuner

3.

IF Filter IF Preamplifier and IF Attenuator

4,

5, IF Amplifier

P

6, 7,

8.

9,

10, Limiter Stages 11, FM Detector 12, AF Amplifier 13, AF Amplifier Ill 14, AF Detector

1

hase-compensator and Ehnd-pass Filter

Buffer Amplifier

AM Detector

IF Output Amplifier

I

and

I1

-

V

5, Power- Suppl y

SECTION SECTION H

G

-

MA1 NTENANCE

PARTS LIST

Modulation Meter

Type AFM2

Section

Fig

.A1

.

The I'tAodulation i'Aeter,

type

AFM2.

The Modulation Meter, type a solid-state, line- or battery-operated precision measuring instrument for ac-

curate measurement of the modu depth of ation of quency range from Modulation Meter cepting telemetric signals with a modulation frequency up to 200 kHz, and

stereo signals for which it features an

L/R-separation of

The

flection for

and

kti~

srnall amount of residual modulation generated in the

er, it and

F"M

measurer( enfs on distol-ted signuls are

AM

signals and the peak devi-

FM

signals in the carrier fre-

5

to 1002 MHz. The

is

designed for ac-

46

dB.

indicating metel- has fuI I -scale de-

3,

76,

30,

53,

*1C,

t

hl\,

is

possible to measure residual

AM

in

signals, and vice versa. Accilrate

k3C1

peak value. Due to the vely

oscillators, sp~~rious

If;GC,

idiodulation Meter plop-

and

AFM2,

lation

1

0C9h

and

AM

is

AM,

zt2C.C

FM

on

A.

Introduction

rendered easy by a

the positive ue to be measured separately. creased resolution nal indicator, such as a voltmeter,

he

ranges downwards.

The input signal level necessury for

occbracy

cy range

range

the range

mcim operating input

Besidzs a manual level control, the Modulation Meter features

level control with a regulating range of

To increase the versatility of the Modulation Meter for row-band equipment, it two kHz, just as three standal-d deen~phasis networks of non-standard of four low-pass filters with frequencies of

3,

pass filter with

15

tions for a wide

A

900-252,

swit2l.l that enables

and the negative peak val-

is

desired, an exter-

e--plo)/ed to extend

is

3

mV in the carrier frequen-

5

to

200

2CC

to

60C

SCO

to 1003 MHz. The maxi-

ihe

MHz,

Mtlz, and

20 mV in the

voltage

40

dB.

nreasvren;ants on nar-

is

IF

bandwidths of *20 and k400

50,

75,

and 750

6

dB/octave (ref. 1 kHz),

15,

75, and 200

kHz,

ensure optimal measuring condi-

Crystal Oscillator Unit, code

is

available. See

kHz,

3

dB points at 50 Hz and

range of applicatio~s.

and ore band-

If in-

con

measuring

full

30

mV in

is

10

V.

an

automatic

provided with

s,

one

SECTION

C,

Section

FREQUENCY RANGE OF INPUT SIGNAL 5

FREQUENCY RANGE OF

VARIABLE Fundamental ranges: 7-12, 12-21, 21 -37, 37-65, 65-1 10, and

OSCl LLATOR

B.

Specifications

-

1002 MHz

7

-

1000 MHz

11 0-200 MHz

Harmonic ranges: CALIBRATION ACCURACY 3% CRYSTAL OPERATION

INPUT LEVEL

Carrier frequency ranges: Attenuation 0 dB Attenuation 10 dB: Attenuation 20 dB:

+

:

200-330, 330-600, and 600-1 000 MHz

An optional Crystal Osci that accepts up to four switch-selected crystals, ensures low residual FM.

Specification changes due to crystal operation: See

SECTION C

One input socket in connection with a 3-step input attenuator (1 0 input levels from

5-200 MHz 200-600 MHz 600-

l lator Unit, code 900-252,

-

ACCESSORIES.

+

10 + 20 dB) ada,pts the AFM2 to

3

mV to 10 V.

1

000 MHz

Attenuation 30

Attenuation 40 dB:

Max.

Input level for residual

I

safe input level: 10 V

Min. input level

dB:

+

Basic sensitivity range,

4-t

Values in parentheses are derived from

BSR

of

FM

and AM measurements:

(

RF attenuation inserted (dB)

and from lower

BSR

limit

of overlapping ranges.

I

minimum

level

l

NPUT IMPEDANCE

50

R

nominal

LEVEL Manual level setting:

Automatic level setting:

FR

MODULATION Deviation ranges:

Accuracy:

*75

SETTING

EQ

LI

E

NCY

kHz deviation:

Continuous within a range of min.

The AGC system keeps the level setting within

0.5%

fied input level ranges, inclusive of the overlapping ranges.

Fine adjustment of the automatic level setting possible

*3,

deviation).

Positive and negative deviation peaks can be mea-

sured separate ly.

2% of reading quencies within

for input level variations within the speci-

.

*lo,

k30, lt100,

+

1

%

of full scale at modulation fre-

20

Hz - 53 kHz

and

*300

40

dB.

kHz f.s.d.

is

(peak

$300

kHz

deviation:

4%

of reading

quencies within 2% of reading

quencies within

7%

of reading

quencies within

15% of reading

quencies within 125 kHz

Notes:

1.

To obtain specified accuracy, the upper frequency limit of the built-in low-pass filter should be switched as follows:

Deviation range upper frequency limit

k3

kHz

k10

kHz

*30

kHz 15 kHz

&I00 A300

kHz 75 kHz kHz

+

1%

of full scale at modulation fre-

10

Hz - 75 kHz.

-t-

1%

of full scale at modulation fre-

20

Hz - 15 kHz.

+

1

%

of full scale at modulation fre-

10

Hz - 125 kHz.

+

1% of full scale at modulation fre-

-

200

kHz.

3

kHz

15

kHz

200

kHz

~andwidths)

(see

2.

The specified accuracies are valid only with the

METER

lower frequency limit

switch set to SLOW.

is

In position FAST, the

160

Hz.

Distortion

k75

kHz deviation:

0.1 10

%

distortion at modulation frequencies within

Hz

-,

15

kHz.

k300

LR-separation of

AF

kHz deviation:

FM

output and meter response

0.2% 20

0.3% 10

0.5% 20

1 10

3%

10

5%

125

stereo signals: For an ideal FM stereo signal (FCC and EBU-stan-

dard), the LR-separation at modulation frequencies within

distortion at modulation frequencies within

Hz

-

53

kHz.

distortion at modulation frequencies within

Hz

-

75

kHz.

distortion at modulation frequencies within

Hz

-

15

kHz.

.5%

distortion at modulation frequencies within

Hz

-

50

kHz.

distortion at modulation frequencies within

HZ

-

125

kHz.

distortion at modulation frequencies-within

kHz

-

200

kHz.

40

Hz

-

15

kHz

is

greater than

46

dB.

(FM):

AF

output:

Meter response:

Residual

FM:

40

Hz

-

15

Within than

46

dB (see above). This corresponds to a departure from a linear phase response of less than and a frequency response within

(40

HZ

-

53

kHz).

Note:

be used.

Within

of the meter

Notes:

1.

used.

2.

METER

the lower frequency limit

On condition of a quiet test room (noise level

<

Less than

range

'The built-in

40

Hz

is

The built-in

The specified response

switch set to SLOW.

60

dB rel.

5-250

2 x 10-4

25

Hz

MHz; typically

kHz, the LR-separation

+0.25%

200

kHz low-pass filter

-

53

kHz, the frequency response

within

200

FM

+0.25%

kHz low-pass filter

pbar.):

(r.m.s.) within the frequency

and

is

valid only with the

In position FAST,

is

160

Hz.

15

Hz (r.m.s.).

-1.5%.

and

is

to be

greater

0.5'

-1.5%

to

Less than typically

100

50

Hz

FM

(r.m.s.) up to

FM

(r.m.s.).

1002

MHz,

Notes:

1

.

0.1 % of ful l deviation range

2.

Minimum

3.

the built-in band-pass filter (50 Hz - 15 kHz) or one of the deemphases (50 used.

RF

input level: See input Level.

is

to be added.

ps or 75

t~s) is

to be

FM

due

to

AM:

Deemphases: Standard deemphases: Deemphasis:

Additional residual

less than 50 pass filter (50 Hz

50,

75,

6dB/oct. (ref. 1 kHz). For frequency response of filter, see Fig.

The deemphasis can be switched off.

Hz

and 750

FM

error due to

(r. m.s.) at 50%

-

15 kHz)

ps,

switchable.

€31

.

is

AM,

used.

AM

is

typically

when the band-

AMPLITUDE

Modulation depth range:

Accuracy: Manual level setting:

MODLILATION

.

Fig.

€31

.

Frequency response of

6

the

3, 10, 30, and 100%

Positive and negative modulation ~eaks can be mea-

sured separately.

2% of reading frequencies within 20 Hz

5% of reading

frequencies within 10 Hz

Notes:

1.

To obtain specified accuracy, the upper frequency

limit of the built-in low-pass filter should be switched

as follows:

+

1%

1

%

dB/oct. filter.

AM

f.s.d.

of full scale at modulation

-

15

kHz.

of full scale at modulation

-

50

kHz.

modulation range upper frequency range

+

3% 3 kHz

10%

30% 75 kHz

1

00% 200 kHz

+

By a 10

upper frequency limit can be extended to 15 kHz.

2. The above accuracies are valid for modulation depths up to 90% AM within the carrier frequency range 15-300 MHz, and up to 30% AM within the carrier frequency range 300-1 002 MHz.

dB

increase in minimum input level, the

15 kHz

Automatic level setting:

AM

distortion:

Carrier frequencies within the range

5

-

300 MHz:

The following typical values are to be added to the above accuracies:

At a modulation frequency of 20 Hz: At a modulation frequency of 50 Hz: At modulation frequencies above 100 Hz, the addi-

tional error

Note:

ic level settings) are valid only with the

set to SLOW. In position FAST, the lower frequency

limit

0.2% distortion at 30% AM and at modulation

quencies within 20 Hz - 15 kHz.

1%

cies within

The specified accuracies (manual and automat-

is

distortion at 90% AM and at modulation frequen-

is

160 Hz.

10

negligible.

Hz - 50 kHz.

6%

of reading.

1

%

bf

reading.

METER

1

switch

fre-

Carrier frequencies within the range 300 - 1002 MHz:

Residual

AM

at CW:

1

%

distortion at 30% AM and at modulation frequen-

cies within

Less than 0.03%

up to 200 MHz.

Less than 0.1

up to 500 MHz.

Less than 0.3% AM (r. m.

up to 1002 MHz.

Notes:

1.

0.1% of full AM range to be added.

2. Minimum

3. The built-in band-pass

is

to be used.

10

Hz - 50 kHz

AM

(r.m.s.) at carrier frequencies

%

AM

(r. m.s.) at carrier frequencies

s.)

at carrier frequencies

RF

input level: See Input Level.

filter (50 Hz - 15 kHz)

AM due to

FM:

Additional error at 550 kHz deviation.

is

less than 0.6% AM (r. m.s.)

AF output Manual level settings:

Automatic level setting:

l

NTERMEDIATE FREQUENCY CHANNEL

Frequency: 2 MHz Bandwidths:

IF

check:

IF

outputi

(AM)

'the frequency response range 20 Hz

The following typical error contributions are to be added to the above frequency response:

At a modulation frequency of 20 Hz: At a modulation frequency of 50 Hz: At modulation frequencies above 100 Hz, the error

contribution

approx. selected.

The meter has a separate scale to facilitate correct

tuning

2

MHz correct frequency tuning and full scale deflection on meter.

is

within 50.5% in the

-

15 kHz.

6%

1

%

is

negligible.

*400 kHz/3 dB and 525 kHz/3 dB, switch-

(IF

=

2 MHz).

IF

signal of 0.2

V

EMF

from 50 Q source at

AUDIO

Bandwidths:

3

kHz filter:

15 kHz filter:

75 kHz filter:

200 kHz filter:

50 Hz - 15 kHz filter:

AF output:

FREQUENCY

CHANNEL

four switchable low-pass filters, 3 kHz, 15 kHz,

75 kHz, and 200 kHz, to be used when measuring

FM

deviation and AM modulation.

for mod. freq. up to for mod. freq. up to 15 kHz. for mod. freq. up to 75 kHz and for measurements of

FM

stereo deviation.

for mod. freq. up to 200 kHz and for measurements

of stereo

(bandwidth: 10 Hz (0.1 dB) Band-pass filter, 50 Hz (3 dB)

to be used when measuring residual

AF signal of deflection.

Bandwidth as specified above. ac- or dc-coupl ing.

L/R

1

separation.

V

3

kHz

-

350 kHz (3 dB)

-

15 kHz (3 dB),

FM

EMF

(peak value) at full scale

A

switch provides for

)

and AM.

ac-coupl ing: Output impedance: 600

pF.

10

dc-coupl ing: Output impedance; 600

Q

in series with

Q.

dc OLITPUTS

IF

level:

1

V

EMF

dc-voltage of

deflection to set level mark.

from 600 R source at meter

IF

frequency:

Modulation:

POWER Power line:

VoI tages:

Frequencies: Consumption:

External dc

dc sources:

Current drain:

TERM1

SUPPLY

NALS

supply:

dc-voltage of deflection to

dc-voltage of scale deflection.

110

V

and 220

48 - 65

about 25 The power cord

plug of the Schuko type.

0

to

approx.

HZ.

+(I8

400

1

V EMF from 600 R source at meter

IF

CHECK mark (50

1

V

EMF

V,

~10%.

VA.

is

fixed and provided with a mains

to 25

Lq

and 0 to -(I8 to 25

mA from each source.

from 500

mV/100

5:

source at full

kHz).

V)

.

RF

input and AF output: dc output

External - dc supply:

Operating ambient temperature range:

DIMENSIONS AND

Height:

Width:

Depth:

Weight:

MOUNTING

ACCESSORIES

(AF):

AND

IF

output:

FINISH

SUPPLl

WEIGHT

ED

B

NC UHF Banana jacks Bel

l

ing Lee

197

mm

485 mm

245 mm

13

kg (28.6 Ibs)

Steel cabinet finished in grey enamel lacquer.

1

coaxial cable

UG-88/U BNC plugs.

type

(7

3/4

(19

(9

5/8 in.)

1.1

1/8

436;'s

in.)

(50

O),

code 017-004, with

ACCESSORIES

AVAl LABLE

1

battery plug, Belling

Crystal Oscillator, code 900-252.

1

set of dust covers (top plate and bottom plate)

for rack mounting, code 884-002

&

Lee,

L1436/P,

code 805-429.

Section

C.

Accessories

PLUG-IN CODE 900-252

General The Plug-in Crystal Oscillator Unit,

code 900-252,

in the frequency range 80 to achieve low residual plied without crystals.

The Crystal Oscillator Unit contains crystal-controlled oscillator followed by

a

doubler stage, and to four switch-selected crystals. The crystals are mounted inside the unit and can easily

ment

CRYSTAL

is

be

exchanged. Initial adjust-

is

made by means

OSCILLATOR UNIT,

preferably used with-

-

1000

MHz

FM.

It

is

sup-

a

it

has room for up

of

individual

Fig.

C1.

The Crystal Oscillator Unit,

code

900-252.

screw-driver adjustments on the front

.

panel The trimmers directly cover a tuning

range of 360

80

-

120

fixed capacitor must be added in parallel

with the trimmer.

MHz

-

1000

and

MHz.

250

In the ranges

-

360

MHz,

a

Specifications

Number of crystals:

sockets for up to

4

crystals.

Frequency of crystals:

lni tial conditions:

In order to achieve the highest possible sensitivity of the modulation meter, the frequency of the crystals must be as high as possible. Overtone crystals

-

100

having frequencies within the range 40 are recommended. The crystal frequency f termined by

f -2

f=

cr 2n

where f indicates the carrier frequency and n the odd harmonic of the crystal overtone-frequency.

The sensitivity specifications, item are based on the following combinations of carrier frequency, order of harmonic, and range of crystal

frequencies.

Carrier frequency

s

f

s

Order of harmonic

MHz

n

l

NPUT

Range of crystal

frequencies

MHz

is

cr

LEVEL,

f

cr

de-

Characteristics of the crystals:

Type:

Frequency: Frequency tolerance: Frequency tolerance over

operating temperature range:

Condition of resonance: Mode of operation: Max. drive level: Max. equivalent series

resistance:

250 - 600 MHz 600 - 1000 MHz

HC-25/U See above. 10 x

10

x

Series

5.

overtone

2

mW

at reference temperature 25

within 0-50'~

3

5

4060

-

0

C

l00MHz

I00

MHz

CHANGE

CAUSED BY THE CRYSTAL OSCILLATOR

lnput level: Frequency ranges: 250

Attenuation 0 dB

IN

SPECIFICATIONS OF AFM2

+

:

-

20 - 100 mV 30 - 100

600 MHz 600 - 1000 MHz

mV Attenuation 10 dB: Attenuation 20 dB Attenuation 30 dB: Attenuation 40 dB:

Max. safe

lnput level for FM and AM

measurements: 250

-

in~ut level: 10

600 MHz:

(60)* (200) (0.6) (2)

+

Basic sensitivity range, BSR

u

level of

ranges.

I

-

100 - 300 mV 100 - 300 mV

-

300 - 1000 mV 300 - 1000 mV

- 1 -

- 3 -

Values

V

Min. input level 1 RF attenuation inserted (dB)

3 V 1 -3V

1OV

in

parentheses are derived from minimum

BSR

and from lower

3-10V

limit

of*overlapping

I

600

-

1000 MHz:

Residual FM:

1

Min. input level

Less than 20 Hz FM (r.m.s.) at carrier - frequencies

to

up

1 . 0.1 % of fu

2. Minimum RF input level: See lnput Level.

3. The built-in band-pass filter (50 Hz or one of the deemphases (50

1002 MHz; typically 15 Hz (r.m.s.).

11

1

RF

attenuation inserted (dB)

deviation range

ps

is

to be added.

-

15 kHz)

or

75 ps)

is

to be used.

(

Residudl AM at

CWo

Less than 0.15% (r.

to 1000

Notes:

1

.

MHz.

0.1 % of full

AM

m.

s.) at carrier frequencies up

range must be added.

2.

Minimum

3.

The built-in band-pass filter (50

is

to be used.

RF

input level:

See Input Level.

Hz

-

15

kHz)

Section

D.

General Description

DESCRIPTION As can be seen on the

diagram shown in signals to the 50 are fed to a diode mixer via an input attenuator providing for 10, 20, 30, and 40 dB attenuation and thus accom-

RF

modating r.m.s. The mixer, which

highly linear, so that distortion of

and

amplitude-modulated signals

is

coupled to the local tuning oscillator.

RF

For

5 to 200 MHz, mixing

the fundnmental frequency of the local oscilla:or, whilst it takes place with the third and fifth harmonics in the range from 200 to 1002 MHz. sults in an mixer can also be coupled to an option-

al Crystal Oscillator Unit,

252, which can accommodate four crystals, thereby enabling measurements at four predetermined, fixed frequencies.

the signal from the mixer through an IF filter, which

linear band-pass filter with of

1400 kHz, a high degree of phase-

linearity being necessary in order to pass a multiplex stereo signal with min-

imum distortion. From the

to an buffer. At the same time, the

IF

signals from 3 mV to 10 V

input signals in the range from

IF

signal of 2 MHz. The

IF

filter, the

preamplifier which acts as a

simplified block-

Fig.

Dl

,

the

Cl

coaxial connector

is

balanced

is

realized with

code

is is

a

bandwidth

IF

signal

RF

input

avoided,

This

re-

900-

passed a phase-

is

fed

IF

pre-

amplifier provides for the

IF signal. gether with ideal coupling to the filter, keeps the noise level down to a minimum at all input levels.

The

IF

preamplifier diode attenuator whose biasing current can be controlled

LEVEL, accessible on the front panel of the Modulation Meter. Level control can be performed within a range of 40 dB. Alternatively, the driven by a voltage proportional to the

IF

level amplified in an AGC amplifier.

This

provides for automatic level control within 40 dB. Fine adjustment theless also possible by means of the

potentiometer

The

IF

signal from the then fed to an sists of two wideband amplifier stages. The

IF

amplifier brings the

the level required by the

The

amplified either through through a phase-compensator, according to the position of the

.

The band-pass filter has a band-

trol

width of

just as the use when measuring on weak signals from narrow-band equipment. The phase compensator leaves the initial bandwidth unchanged.

A25

This

LEVEL.

IF

1F

a

kHz and

IF

filter. It

ahplification of

amplification, to-

is

followed

by

the potentiometer

IF

attenuator can be

IF

attenuator

amplifier which can-

AM

signal

band-pass filter or

is

then passed

IF

BANDWIDTH con-

is

phase-linear

is

intended for

is

IF

signal to

detector.

by

never-

IF

a

is

A buffer amplifier separates filters, AM

detector and sists of a unity-gain amplifier with low output impedance and serves to suppress any influence from the is

available for external monitoring from

a coaxial connector on the front panel.

IF

The

is

fed both to the AM detector and to

the

IF

output amplifier. The AM detec-

tor

is

an amplifier with a mean-value

detector in the feedback loop which

also provides for the large amount of linearity required. The AM detector has

a

dc and an ac output. The first of these strument via the FUNCTION selector.

In the corresponding position of the FUNCTION selector, the meter indicates the value of the AM detector's

dc current

el. The second output of the AM detector below) via the selector FUNCTION.

As stated above, the buffer amplifier

output amplifier which provides for amplification so that the level required for driving a following limiter

The limiter transforms the a square wave, the zero crossing of

which

peak-to-peak value being compared with

variations in the mean value. Subsequent

limiting action takes place in the following limiter section. The resulting signal

is

detector section which consists of a

monostable multivi

amplifier. The signal from the last limiter section

is

vibrator which provides for pulses of constant width. The tivibrator are amplified in an output amplifier. The output

with a regulating loop consisting of a

peak detector and an amplifier. regulating loop keeps the value of the peak-to-peak voltage of the output am-

is

coupled to the AF section (described

is

fed via a buffer amplifier to the

used to trigger a monostable multi-

IF

output amplifier. It con-

IF

output which

signal from the buffer amplifier

coupled to the meter of the in-

-

in other words: the IF lev-

IF

signal from the

is

also fed to the

is

obtained.

IF

signal into

controlled by variations in the

IF

FM

brator and an output

pulses from the mul-

amp1 ifier

is

provided

This

pl ifier constant. Hence, as the amplitude and the width of the pulses are constant, the mean value of the signal will vary according to the number of pulses per second. The mean value

when the

sition IF CHECK for reading the value of the intermediate frequency. To ensure a

high degree of accuracy and an extreme-

ly low hum level, both the multivibrator

and the output amplifier are furnished

with their own regulated power supply.

From the AM or

is

fed to a low-pass filter via a relay controlled by the FUNCTION selector. The low-pass filter features the

gree of ing stereo information without any disturbing influence on

The low-pass filter two-section, uator which determines the metering ranges. providing for amplification signal to the level required by the next stages.

The AF amplifier phasis networks providing for the stan-

dard deemphases of 50, 75, and 750

and the non-standard deemphasis of dB/oct. The amplified AF signal can also be passed through one of four pass filters with frequencies of

75 and 200 kHz, or through a

pass filter with 3 dB points at 50 Hz and 15 applications.

These networks and filters are followed by an AF amplifier. from this amplifier front panel via the AF OUTPUT connector for distortion measurements or external monitoring. OUTPUT does not interfere with the me-

ter indication. The output voltage from the first AF amplifier other AF amplifier providing for the voltage necessary for the AF detector. The signal from the AF OUTPUT can either be dc-coupled or ac-coupled to

FUNCTION selector

FM

detector, the signal

phase-l inearity required for pass-

L/R

is

4

x 10 dB precision atten-

It

is

followed by an amplifier

is

followed

kHz,

ensuring a wide range of

is

utilized

is

in po-

high de-

separation.

followed

of

by

the

deem-

a

AF

pi,

6

low-

3,

15,

band-

The output signal

available on the

Loading of the AF

is

also fed to an-

q-

-

R

F

Input

XI1

R

F Local

Att.

t

Mixer

-

ROMAN FIGURES REFER TO

DIAGRAM NUMBER

*.N AUTO

TUYlYC

\

osc.

..,,,""""G

/

111

\

I

Em

/

"!t!!%!!!H

,,9.".

u

..O~.".

I

v

I

-

11

IF Frequency

"~*.!tEE

4s

I

1

I F

111

IF

Output

1

L

\r

VI

7,

VII

10

2"

\

Att.

XI1

-

Low Pass

Filter

\\

Vlll

\

'

-

\

_FM+

IF Check

/

"-

/

I..,~.

-8

VIIL

/

Fig.

Filters

Deem-

phases

/

I

$.YE!.!

Kl°C

m

Dl

. Block-diagram of

-

IF

Level

I

x

olF Check

I

the

\

1.

\

,,"El

.SZ.<G.

SLOW

lbl,

WG- ,C".,U

I

l__(.l.l,l.l,e*.

Em

Modulation

Meter,

\

I.

C*ICI

type

\

Y%"

zi::

AFM2.

IF

CHICI

Level

the AF OUTPUT connector by sliding

the switch.

tions according to the position of the switch MAN.-AUTO.

The AF detector gives the true peak value of any AF signal. Depending on the position of the FUNCTION selector, the positive or the negative modulation peak can be measured. The AF detector has

two time constants, thereby furnishing

two meter responses. The AF detector

pedance-matching network providing for

low output impedance to the meter.

CONTROLS, General

As can be seen in Fig. D2 and Modulation Meter, type

provided with the following controls,

meter, and terminals: Controls, Meter, and Front Plate Termin-

als (see Fig. D2)

Power Lamp and

The power switch monitored

RANGE Selector and Drum Scale (2) The selector RANGE

tion rotary switch. In the first six po-

sitions, the RANGE selector provides

for selection of the frequency ranges according to the table printed on the front plate of the instrument. (Note that the ranges frequency bands.) The next position a rest position. In the last position, the plug-in Crystal Oscillator Unit (if any)

is

monitored

ately above. TUNING Knob (3)

The knob TUNING provides for adjust-

ment of the local oscillator frequency

at

2

is

monitored by a cursor on the drum scale.

LEVEL Potentiometer (4) and MAN.

AUTO. Switch

by

is

connected. The selector

MHz from the signal frequency. It

is

followed

METER,

the lamp POWER.

E

by

AND

ON

switch (1)

OIV

is

and F .each cover two

the drum scale immedi-

by

TERMI

D4, the

AFM2,

a toggle switch

an eight-posi-

(5)

an im-

NALS

is

RANGE

-

When the switch MAN. -AUTO. position ter

instrument manually within a range of

min. 40 dB. When the switch MAN.-AUTO.

,position AUTO., the LEVEL potentiome-

ter automatical

i

nstrument. FUNCTION Selector The selector FUNCTION

position rotary switch. The position

LEVEL

nal

IF

level. When measuring, the positions

IF

ment to the exact carrier frequency. (See under "Meter" below) The percentage of amplitude modulation of AM signals can be measured by placing the

selector in position AM cording to the sign of the modulation peak to be measured. The frequency deviation of sured

FM

the modulation peak to be measured.

METER

'the selector position rotary switch. Each position corresponds to the fu

the meter, viz: AM

loo%,

METER

The switch

In position SLOW

meter response should not be used when measuring on signals with modulating frequencies higher than 160 Hz.

mod

fast.

IF

MAN.,

is

used to vary the sensitivity of the

is

used for fine-adjustment of the

ly adjusted sensitivity of the

the LEVEL potentiome-

(6)

is

a

is

used when searcfiing the sig-

(i.e., tuning) and monitoring the

CHECK are used to tune the instru-

+

or AM - ac-

FM

signals can be rhea-

by

placing the selector in position

+

or FM - according to the sign of

RANGE

FM3

Switch

>I60 Hz, the meter response

BANDWIDTH

Selector

METER

-

10

-30

(8)

METER

is

(9)

(7)

RANGE

l

I-scale range of

3

-

10 - 30

-

100

-

is

a sliding switch.

fmod >10 Hz, the

slow. This position

In

position FAST

is

seven-

is

a five-

300kHz.

in

-

is

The potentiometer LEVEL has two func-

The switch IF BAbIDWIDTH

is

a sliding

Fig.D2. Front plate of the Modulation Meter, type AFM2.

switch. It provides for switching from the band-pass filter to the phase-comparator and vice versa, width of k25 kHz to one of k400kHz.

AF

FlLTER/DEEMPHASIS Selector (1 0)

The selector AF a nine-position rotary switch. In the scales. first position

a

band-pass filter

used when measuring residual AM and

FM.

kHz

REO),

pass filters are switched in. They are used when measuring

AM

filters are used for modulation frequencies up to 3 kHz and 15 kHz, respective-

In the next four positions - 200

(L/R

STEREO), 75 kHz

15 kHz, and 3 kHz - four low-

modulation. The 3 kHz and 15 kHz

FI

-

50 Hz- 15 kHz (3 dB)

i

.

e

.,

from a band-

LTER/DEEMPHASIS

is

switched in. It

(A

f,

FM

deviation or

is

-

is

STE-

IY.

is

The 75 kHz filter tion frequencies up to 75 kHz and for measurements of The last filter - 200 kHz modulation frequencies up to 200 kHz and for measurements of stereo L/R separation (bandwidth: 10 Hz (0.1 dB)

-

350 kHz (3 dB)

The last four positions of the AF FILTER/ DEEMPHAS

emphases of 50

IS

selector introduce four de-

p,

used for modula-

FM

stereo deviation.

-

is

).

75p

(European and

used for

American standard for stereo work), 750

ps (narrow-band equipment) and a 6 dB/

oct (non-standard)

Meter

The meter of the Modulation Meter, type sion type. It

The upper scale

ing in the AM ranges from

0 to

or from viation, according to the positions of the FUNCTION selector and the RANGE selector. It with a LEVEL mark to permit setting of

IF

the

The middle scale (12) provides for read-

ing in the AM ranges from 0 to 3% or

0

to 30%, and in the 0 to 3 kHz, Oto30kHz, or 0 to 300 kHz deviation, according to the position

of the FUNCTION and

I

ec tors.

se

The lower scale (13) checking the frequency of the converted

signal. viation around the 2 MHz intermediate

frequency. An for exact tuning to the intermediate fre-

quency

AFM2,

loo%,

0

to

level.

It

.

is

of the taut-band suspen-

is

provided with three

(1

1)

provides for read-

0

to 10%

and in the

10

kHz or 0 to

is

graduated for k300 kHz de-

IF

CHECK mark provides

FM

ranges

100

kHz de-

also provided

FM

ranges from

METER

is

utilized when

RANGE

METER

lOdB lOdB 20dB

Fig. D3. Attenuation and sensitivity ranges.

FREQUENCY RANGE

15

-

200

MHz

ATTENUATION

0 dB 3-100mV 20-100mV 30-100mV

200 - 600

MHz

600 - 1000

MHz

AF

OUTPUT

Connector The AF

switch used for selection of the mode of coupling of the AF signal. With the switch in the left-hand position, the AF signal with

10

right-hand position, the AF

coupled (600 R). The AF signal of

EMF

(peak value) at full-scale deflec-

tion

is

delivered via a UHF connector.

RF

INPUT

The BNC connector

for connection of the measured on.

Input Attenuator The input attenuator

tenuator to adapt the Modulation Meter, type AFM2, to input levels from 3 mV to

10

V.

As

degree of attenuation to be selected depends on the input voltage range, and

the sensitivity of the instrument on the frequency range.

IF

OUTPUT

The UHF connector for connection of the 2 MHz

to, for example, external monitors. It delivers a 2 MHz

EMF

from a 50 ohms source at correct frequency tuning and full deflection on the meter.

Plug-in Unit Receptacle

The Modulation Meter, type

is

so designed that two optional

Switch and AF OUTPUT

(1

4)

OUTPLIT switch

is

ac-coupled (600 R in series

$).

With the switch in the

Connector

RF

(1

6)

is

(10

+

10 + 20 dB). It

can be seen in Fig. D3, the

is

a sliding

signal

is

(15)

INPUT provides

RF

signal to be

a three-step at-

is

(17)

IF

OUTPUT provides

IF

signal

IF

signal of 0.2 V

(1

8)

AFM2, dc supply be means of a Belling & Lee

lug-in

dc-

1

V

used

units, code 900-252, and External-Oscillator Amplifier, code 900-253, can be easily plugged in. CESSORIES.)

Rear Terminals (see Fig. D4)

IF

The terminal banana jacks (600 output voltage of flection to

IF

The terminal banana output voltage of

deflection to MOD. The terminal MOD.

of two banana a dc output voltage (meter current) of V

Line Voltage Indicator (4) The line voltage indicator shows the

line voltage to which the instrument switched: either to 65

(6) are loosened, the voltage indicator can be turned to the appropriate position. (For further details see SECTION

E

Battery The terminals BATTERY are of the Belling

&

nection of the instrument to an external

L1436P Plug supplied with the instrument.

i.e., Crystal Oscillator Unit,

(See SECTION C

LEVEL (DC)

FREQ. (DC)

iacks (600

LEVEL

(1)

IF

LEVEL

R) and delivers a dc

1

SET

LEVEL

(2)

IF

FREQ.

IF

CHECK mark.

(DC) (3)

consists of two

V

EMF

mark.

consists of two

R)

and delivers a dc

1

V

EMF

LEVEL

iacks (600 R) and delivers

EMF

at full-scale deflection.

11

0

V

or 220 V - 48

Hz.

When the two screws (5) and

-

OPERATING INSTRUCTIONS.)

-

AC-

at meter de-

at meter

(DC) consists

(7)

Lee L1436/5 type and provide for con-

is

1

Fig.D4. Rear terminals of the Modulation Meter, type

AFM2.

Section

Before connecting the instrument to the power line, make sure that the supply transformer and the line voltage indicator are set to the voltage of the power

l

ine.

To prepare the instrument for

220

V

line voltage operation, refer to

diagram XI and proceed as follows:

1)

If the instrument must be used at a

line voltage of

3

and 5 and lugs 4 and 6 on the sup-

ply transformer.

2)

If the

line voltage of

4

and 5 on the supply transformer.

Then loosen the screws on the voltage indicator and set the indicator to the

desired voltage.

MEASLIRI

instrument must be used at a

NG

11

0

V,

interconnect lugs

220

V,

interconnect lugs

AMPLITUDE MODULA-

110

E.

V

or

Operating Instructions

3)

Set the switch BANDWIDTH to

kHz when measuring on broad-band equipment, or to suring on narrow-band equipment.

4)

Set the switch

the modulation frequency of the signal

is

less than

160

FAST.

5) Set the switch

MA

N

.

6)

Set the drum scale to the desired frequency range selector.

7)

Set the selector FUNCTION to LEV-

EL.

8)

Set the tuning knob so that the cur-

sor on the drum scale indicates the signal frequency so as to obtain maximum meter deflection.

*2

rt400

*25

kHz when mea-

METER

Hz; otherwise set it to

MAN.

by

using the RANGE

MHz, and then tune

to SLOW if

-AUTO. to

Modulation Percentage of AM Signals

1)

Feed the signal to be measured to

RF

the that the max. applicable signal r.m.s., and that the input impedance

is

2)

ing to the instructions printed on the

front panel, or refer to Fig.

TION

INPUT connector. Bear in mind

50

R.

Use the RF input attenuator accord-

D

-

GENERAL DESCRIPTION.

D3

is

10

V

in SEC-

9)

Turn the selector FUNCTION to

CHECK.

10)

Make a fine adjustment with the

TUNING knob so that the meter reads

IF

CHECK.

11)

Set FUNCTION to LEVEL. When using MAN.-AUTO. in position MAN. readjust to the sary by means of the LEVEL potentiometer. When using MAN. -AUTO. in position AUTO., fine level-adjustment can

LEVEL mark, if neces-

IF

be accomplished by means of LEVEL.

It

is

recommended to use the AUTO. switch in position AUTO. when performing evitable level variations of the signal then are equalized.

12) In order to obtain

select the low-pass filter corresponding

to the modulation frequency of the

Modulation Frequency

50 kHz

15 kHz

AM

measurements, as the in-

the

MAN.

best accuracy,

-

sig-

El,

nal under test. See Fig.

SECTION

to der

"AM

13)

Turn FUNCTION to

depending on which peak of modulation

is

to be measured.

14)

Rotate the selector

until a proper deflection

15)

Read the modulation percentage. Check if the reading both peaks of modulation: a difference indicates distortion of the modulation envelope. See Fig. SECTION

"AM MODULATION Distortion".

Residual AM on

B

-

SPECIFICA'I'IONS un-

MODULATION Accuracy".

AM

METER

is

E2, and refer to

B

-

SPECIFICATIONS under

FM

Signals

and refer

+

or AM

RANGE

is

obtained.

the same for

-

,

20 Hz

c

-

10 Hz

5 MHz

Fig. percentage measurements.

Modulation Frequency

50 kHz

15 kHz

20 Hz

10 Hz

5 MHz

Fig.

percentage measurements.

-5%of reading + 1% of f.s.d.-

El

.

Accuracy of modulation

E2.

Distortion for modulation

-

-+

Carrier

300MHz 1002 MHz

300 MHz 1002 MHz

Frequency

Carrier Frequency

Proceed as described above. If resolu tion somewhat higher than that corresponding to the 3% AM range external meter, e. g., an electronic voltmeter, may be connected to the AF OUT-

PUT connector. The external meter will read

1

volt for full deflection of the in-

ternal meter, RANGE selector set to

tion percentage read on the voltmeter

is

0.003% per mV.

The minimum residual AM reading for a given deviation caused by the instrument itself can be estimated as follows:

1)

Apply

to LEVEL.

2)

Rotate the TUNING knob back and

forth so that the intermediate frequency

is

changed over the range 2 MHz - A f to 2 MHz viation of the frequency-modu lated sig-

nal whose residual AM (Check the frequency change with the

IF

CHECK scale.)

3) Read the

change in the LEVEL reading. The minimum residual AM

this percentage change.

i.e., with the

a

CW

signal and set FUNCTION

+

Af, where Af

peak-t~-~eak value of the

is

wanted, an

METER

3,

the modula-

is

the de-

is

to be measured.

approx. half of

-

MEASURING FREQUENCY DEVIATION

(FM

kHz)

FM

Frequency Deviation of

1)

Feed the signal to be measured to

RF

the that the and

2)

ing to the instructions printed on the front panel, or refer to Fig. D3 in SEC-

TION

3)

k400

equipment, or to suring on narrow-band equipment.

4)

the modulation frequency of the is to

5) Set the switch MAN.-AUTO. to

MA

INPUT

hax. applicable signal

thatthe input impedance

Use the

D

Set the switch

kHz

Set the switch

less than 160 Hz; otherwise set it

FAST.

1\1.

connector. Bear in mind

RF

input attenuator accord-

-

GENERAL

IF

when measuring on broadband

k25

METER

signals

is

10

is

50

R.

DESCRIPTION.

BANDWIDTH to

kHz

when mea-

to SLOW if

signal

V

E3,

signal under test. See Fig. to

SECTIOI\I

"FM MODULATION

der

13)

Turn

depending on which peak of modulation

is

to be measured.

14) Rotate the selector

until a proper deflection

15) Read the modulation deviation. Check if the reading

Modulation Frequency

200

kHz

125

kHz

75

kHz

53

kHz

15

kHz

----

---2%

B

-

SPECIFICATIONS un-

FUNCTION

15% of readinq + 1% of f.s.d.

7%of reading + l%of f.s.dr 4%of readinq + 1%of f.s.d.

---

---------

of

reading

+1%

to

FM

METER

is

of

t

and refer

-

Accuracy".

+

or

FM

RANGE

is

obtained.

the same for

I

-,

6)

Set the drum scale to the desired frequency range by using the RANGE selector.

7)

Set the selector

FU

NCTlON to LEV-

EL.

8)

Set the cursor on the drum scale indicates the signal frequency tune so as to obtain maximum meter deflection.

9)

Turn the selector FUNCTION to IF

CHECK.

10)

Make a fine adjustment with the

TUNING

52

knob so that the

MHz, and then

TUNING knob so that the meter reads

IF CHECK.

11)

Set the selector FUNCTION to

EL. When using

tion

MAN.,

When using MAN.-AUTO. in position AUTO., fine level-adjustment can be accomplished by means of LEVEL.

12)

in order to obtain the best accura-

cy, select the low-pass filter corresponding to the modulation frequency of the

MAN.-AUTO.

readjust to the LEVEL mark.

LEV-

in posi-

20

Hz

10

Hz

')

Fig.

deviation measurements.

Modulation Frequency

200

kHz

125

kHz

75

kHz

53

kHz

Fig. deviation measurements.

4%of reading + l%of f.s.d.

7%of reading + 1%of f.s.d. +75

E3.

Accuracy of frequency

E4.

Distortion for frequency

*75

kHz

Frequency Deviation

1300

Deviation

*300

kHz

Frequency

kHz

both peaks of modulation: a difference

indicates distortion of the modulating

envelope. See Fig.

SECTION

"FM

B

-

MODULATION - Distortion".

E4, and refer to

SPECIFICATIONS under

Residual

Proceed as described immediately above. Because of the very effective limiter

stages in the

FM

quite low, viz. 50 Hz (r.m.s.) at 50% AM when the band-pass filter (50 Hz

15 kHz)

carrier frequency within 15

is

less than 25 Hz

less than 100 Hz

1

002 MHz, when measurements are performed in a room with an acoustical noise level lower than 60 dB (rel. 2

10-4 pbar) and the band-pass filter (50 emphases (50 ps or (See SECTION

If a resolution somewhat higher than that corresponding to the 3 kHz deviation range

meter can be connected to the AF OUT-

PUT

read internal meter,

switch set to thi: electronic voltmeter will be 3 Hz per

US1

IN UNIT, CODE 900-252

FM

on CW and AM sianals

FM

detector, the residual

caused

Hz

terminals. The external meter will

1

mV.

NG

by

amplitude modulation

is

used. The residual

FM

(r.m.s.) up to

-

15 kHz) or one of the de-

75

B

-

SPECIFICATIONS.)

is

wanted, an electronic volt-

volt for full deflection of the

i.e., with the

3,

the deviation read on

A CRYSTAL OSClLiATOR PLUG-

FM

at a

-

250 MHz

(r. m. s.), and

:IS)

is

used.

METER

is

-

Fig.

ES.

The arrows show screws and plate to unit

Crystal Oscillator Unit (see Fig. E5).

2) Supply the Crystal Oscillator Unit with Crystals. Bear in mind that the crystals must have the frequency f defined below:

where fs indicates the carrier frequency

and n the odd harmonic of the crystal

overtone frequency. The sensitivity spec-

ifications (see item

SECTION C

are based on the combinations shown

below of carrier frequency, order of harmonic, and range of crystal fre-

quencies.

3) Position the Crystal Oscillator Unit in the Modulation Meter and fasten the

two screws.

be

removed when a pl!-i.2-in

is

to be used.

is

f -2

f=

c

r 2n

S

-ACCESSORiES or Fig. E6)

MHz

INPUT LEVEL in

to be placed

C

r

1) Remove the two screws and the plate

covering the receptacle in which the

Carrier frequency

Order of harmonic

4)

Switch the

tion

G

RANGE

-

"CRYSTAL OSCILLATOR".

Range of

selector to posi-

-rystal freqbencies

5)

Tune the Modulation Meter to the

desired carrier frequency.

6)

Switch the function selector to IF

CHECK.

7)

Switch to the desired channel by means of the four-position selector.

8)

Insert a screwdriver in the hole corresponding to the selected channel, and adjust the corresponding trimmer until the meter indicates

the

Crystal Oscillator Unit

IF

CHECK.

9)

If

necessary, repeat steps

until all four channels are trimmed.

10)

'the Crystal Oscillator Unit, code

900-252,

Proceed as described above for

FM

measurements, but keep in mind that certain specifications of the Modulation Meter proper cannot apply, and refer to SECTION C under "Change in Specifications of AFM2 Caused by the Crystal Oscillator Unit", and see Fig.

is

now ready for use.

FREQUENCY RANGE

6

AM

to 9

or

E3.

Fig.

E6.

Attenuation and sensitivity ranges when the Crystal Oscil lator Unit,

code 900-252,

is

in use.

AT'TENUATION

0

dB

10

dB

20

dB

30

dB

40

dB

250 - 600

20 - 100 rnV 100 - 300 rnV 300 - 1000 rnV

1

3-1OV

MHz

-3V

6.00

-

1000

MHz

30 - 100 rnV

100 - 300 rnV

300 - 1000 mV

1

-3V

3-1OV

Section

F.

Technical Description

RF

l

NPUT CIRCUIT

RF

The connector on the front plate of the instrument, then passed through a resistive attenuator

20

which of the mixer and to adapt the Modula-

tion Meter to 3

mV to 10 V r.m.s.

All

numbered between 1300 and 1399. TUNER (See diagram No.

The local oscillator consists of (2103 in a common-base Hart ley same circuit configuration ranges. Only the tank circuit and LA) and the emitter capacitor CA are exchanged to obtain the different fundamental ranges from

Up to 200 MHz, the mixing takes place

with the fundamental frequency of the

local oscillator. Mixing with input signals which have a frequency higher than 200 MHz

or 5th harmonics of the local oscillator. The intermediate frequency

be used; however, only the lower sideband can be used at 5 MHz because the lower frequency limit of the local oscillator

input signal

dB, 30 dB or

is

inserted to avoid overloading

RF

components of the

is

accomplished with the 3rd

2

MHz, and both sidebands can be

is

fed to the BNC

(~rovidin~ for 10 dB,

40

dB attenuation)

signals in the range

RF

attenuator are

1)

coupl ing . The

is

used in all

(CC, CB,

7

to 200 MHz.

is

chosen to

RF

input signal

is

7

MHz.

With the selector

CRYSTAL OSCILLATOR, the local os-

cillator

lator providing for operation at a fixed

frequency, such as the Crystal Oscil-

lator Unit, code

The signal from the that from the local oscillator or the

Crystal Oscillator Unit are fed to the diodes balanced mixer and provide for good insulation between the input terminals and the local oscillator or the Crystal cillator Unit, and thereby reduce the

influence of stray radiation. The resulting 2 MHz signal via

The tuner lias its own current limiters, i.e.,

-12 Al l components of the tuner are num-

bered between 100 and 199.

IF

The output impedance of the mixer matched capacitively to that of the filter. In this fashion, variations of the output impedance of the mixer become uncritical. From frequency signal of a band-pass filter which mixing products.

type, and it has a bandwidth of

is

disconnected, and an oscil-

CRlOl to CR104 which form a

T102.

QlOl

for +12

v.

FILTER (See diaaram No. ll)

RANGE

900-252, may be used

RF

is

fed to the

V,

TI

02, the intermediate

2

It

is

in position

attenuator and

Os-

IF

filter

and Q102 for

is

IF

MHz passes through

reiects unwanted

of the phase-linear

*400

RADIOMETER AFM2 Operating Instructions Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Artek Media

www.artekmedia.com

Deviation