Equipment information:

Racal 409 Level Meter
Manufacturer:
Racal
Model: 409
Date:
Category: Measurement instruments
Group: Level Meter
Description: Modulation Meter
Information:
                                    
1.1	The Modulation Meter Type 409 is a wide range, highly
sensitive instrument designed to measure percentage
amplitude modulation (a.m.) of carriers from

3	- 1200MHz, and frequency deviation (f.m.) on carriers from
3 - 1500MHz. The meter scales are 0 - 10%, 0 - 30% and 0 -
100% a.m. and 0 - 3kHz, 0 - 10kHz,

0 - 30kHz, 0 - 100kHz, 0 - 300kHz and 0 - 600kHz deviation.
Outputs at the intermediate frequency (nominally 1MHz) and
at l.f. are available at front panel terminals and an
in-built, switched noise filter permits measurement of very
narrow f.m. deviations using a sensitive external l.f.
millivoltmeter.

1.2	Changes in mean carrier level when a.m. is applied can
be measured to better than 1% accuracy and effective i.f.
limiting permits measurement of

spurious f.m. on a.m.

1.3	An f.m. calibrator circuit, which can be checked
directly on an electronic counter, is provided within the
instrument to enable periodical calibration

to be carried out. Tuning the instrument at very high
frequencies has been simplified by the provision of a fine
tuning control and a SET I.F. position on the meter switch.

In this position the tuning control is simply adjusted until
the meter reads to the SET I.F. mark, thus eliminating
tedious peaking procedures.

1.4	The instrument is fully stabilised against changes in
mains supply voltage of ┬▒10% from the value set on the mains
voltage selector. The power

consumption is approximately 120 VA. The instrument is
supplied in a metal case with quickly detachable top, base
and sides. A rack mounting kit is available.

These manuals are available for the above equipment:

Racal -- 409 -- Service and User Manual
File name: Racal-7288-Manual-Page-1-Picture
Manual Type: Service and User Manual
Pages: 57
Size: 2.31 Mbytes (2422836 Bytes)
Language: english
Revision:
Manual-ID/Number:
Date:
Quality: Scanned document, all readable.
Upload date:
MD5: 659b355498dc0e7f9bea60d273e32c97
ed2kID: 89ed8f1d08eeba34bd447538f761736b
Downloads: 15 since 25 October 2015
Information:
PART 1	TECHNICAL SPECIFICATION

PART 2	DESCRIPTION OPERATION AND MAINTENANCE

SECTION 1 INTRODUCTION....................1

SECTION 2 INITIAL PREPARATION ................2

SECTION 3 OPERATION ....................3

3.1.	Tuning Procedure .. .. .. ..	3

3.2.	Measurement of Amplitude Modulation .. ..	4

3.3.	Measurement of Change of Mean Carrier Level ..	5

3.4.	Measurement of Frequency Modulation .. ..	5

3.5.	Monitoring Facilities .. .. .. ..	7

3.6.	FM Calibrator.. .. .. .. ..	7

3.7.	EXTERNAL OSCILLATOR Facility .. ..	8

3.8.	Anti-Microphonic Turret Mounting .. ..	8

3.9.	Measurement of a radiated signal .. ..	8

SECTION 4 CIRCUIT DESCRIPTION ................9

4.1.	General .. .. .. .. ..	9

4.2.	Input, Mixing and IF Amplifier .. ..	10

4.3.	AM Measurements .. .. .. ..	10

4.4.	FM Measurements .. .. .. ..	11
SECTION 5 MAINTENANCE	15

5.1.	General .. ..	..	..	..	15

5.2.	Fault Finding .. ..	..	..	..	15

5.3.	Preset Controls ..	..	..	..	15

5.4.	Adjustment of RV1 ..	..	..	..	15

5.5.	Adjustment of RV10 ..	..	..	..	15

5.6.	Adjustment of RV5 ..	..	..	..	15

5.7.	Alignment of the IF Amplîfier ..	..	..	16

5.8.	Adjustment of RV3, RV6,	RV8, RV13 and RV14 ..	17 5.9
Adjustment of RV15 ..	..	.
5.10.	Adjustment of RV12 .. .. .. ..	19

5.11.	Adjustment of the Preset Components of the FM
Calibrator .. .. .. .. ..	19

5.12.	RF Alignment .. .. .. ..	20 Table 1: Voltage
Measurements .. .. ..	22
PART 3	LIST OF COMPONENTS	29

PART 4	ILLUSTRATIO NS AND DIAGRAMS Fig. No.

1	Type 409 : Block Diagram

2	Type 409 : Circuit (Sheet 1)

3	Type 409 : Circuit : Power Supply

4	Type 409 : Service View (Upperside)

5	Type 409 : Service View (Underside)
Racal-7288-Manual-Page-1-Picture
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