HP 8616a schematic

TM 11-6625-2820-14&P

TECHNICAL MANUAL

OPERATOR'S, ORGANIZATIONAL, DIRECT SUPPORT, AND

GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

FOR

SIGNAL GENERATOR SG-735 / URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6625-00-254-6671)

HEADQUARTERS, DEPARTMENT OF THE ARMY

JULY 1977

d-

●

*

TM 11-6625-2820-14&P

C2

CHANGE

HEADQUARTERS

DEPARTMENT OF THE ARMY

No. 2

Washington, DC, 1 January 1988

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT

AND GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

(INCLUDING DEPOT MAINTENANCE REPAIR PARTS AND SPECIAL TOOLS)

FOR

SIGNAL GENERATOR SG-735/URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6625-00-254-6671)

TM 11-6625-2820-14&P, 22 July 1977, is changed as follows:

Remove old pages and insert new pages as indicated below. New or changed material is indicated by a vertical bar

1.
in the margin of the page. Added or revised illustrations are indicated by a vertical bar adjacent to the identification
number.

Remove pages

Insert pages

iii and l-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..iii and l-O

5-17 and 5-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-17 and 5-18

2. File this change sheet in the front of the publication for reference purposes.

Distribution authorized to the Department and DOD
for official use or for administration or operational purposes. This determination
was made on 1 October 1967. Other requests for this document will be referred
to Commander, US Army Communications-Electronics Command and Fort
Monmouth, ATTN: AMSE1-ME-P, Fort Monmouth, NJ 07703-5000.

contractors only

DESTRUCTION NOTICE – Destroy by any method that will prevent disclosure of
contents or reconstruction of the document.

By Order of the Secretary of the Army:

Official:

R.L. DILWORTH

Brigadier General, United States Army

The Adjutant General

DISTRIBUTION:

To

be distributed in accordance with DA Form 12-36 literature

requirements for SG-735/URM-165.

CARL E. VUONO

General, United States Army

Chief of Staff

TM 1 1-6425-2820-14&P

Cl

CHANGE

No. 1

HEADQUARTERS

DEPARTMENT OF THE ARMY

WASHINGTON, DC, 11 October 1978

Operator's, Organizational, Direct Support, and

General Support Maintenance Manual

Including Repair Parts and Special Tools Lists

(Including Depot Maintenance Repair Parts and Special Tools)

For

SIGNAL GENERATOR SG-735/URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6626-00-254-6671)

This Changes is current as of 16 June 1978.

TM 11-6625-2820-14&P, 22 July 1977, is changed as follows:

1. The title is changed to read as shown above.

2. Remove old pages and insert new pages as indicated below.

3. New or changed material is indicated by a vertical bar in the margin of the page.

Remove Pages

i. ii, and iii
6-9 through 6-12
111-3 and III-4
IV-1 and IV-2 (unnumbered)

4.

File this change sheet in front of the publication for reference purposes.

Insert Pages

i through iv
6-9

111-3 and III-4
IV-1 through IV-31

TM 11-6625-2820-14&P

By Order of the Secretary of the Army:

Official:

J.C. PENNINGTON

Brigadier General, United States Army

The Adjutant General

Distribution:

Active Army:

TSG (1)
USAARENBD (1)

USAINSCOM (2)
TRADOC (2)
DARCOM {2)
TECOM (2)
OS MAJ COMD (2)
USACC (2)
HISA (Ft Monmouth) (26)
Armies (1)
USASIGS (10)
Svc Colleges(1)
Ft Carson (5)
Ft Gillem (10)
Ft Huachuca (5)
Ft Richardson (CERCOM Ofc) (1)

WSMR(l]
USAERDAA (l)
USAERDAW (1)
Army Dep (1) except

LBAD (10)
SAAD (30)
SHAD (3)

(14)

TOAD
USA Dep (1)
Sig Sec USA Dep (1)
Units Org Under Fol TOE:

29-134

29-136

(1 cy each unit)

29-207

29-610

(2

copies each

unit)

BERNARD W. ROGERS

General, United States Army

Chief of Staff

ARNG:

None

USAR:

None

For explanation of abbreviations used, see AR 310-50.

U.S. GOVERNMENT PRINTING OFFICE: 1979-603-028/596

This manual contains copyright material reproduced by permission of the Hewlett-Packard Company.

TM 11-6625-2820-14&P

ECHNICAL MANUAL

T

No. 11-6625-2820-14&P

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, AND

GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

(INCLUDING DEPOT MAINTENANCE REPAIR

SIGNAL GENERATOR SG-735/URM-165

HEADQUARTERS

DEPARTMENT OF THE ARMY

WASHINGTON, DC, 22 July 1977

PARTS AND SPECIAL TOOLS)

FOR

(HEWLETT-PACKARD MODEL 8616A)

( NSN 6625-00-254-6671 )

REPORTING OF ERRORS

You can improve this manual by recommending improvements using DA
Form 2028-2 located in the back of the manual. Simply tear out the self ad­dressed form, fill it out as shown on the sample, fold it where shown, and drop
it in the mail.

If there are no blank DA Forms 2028-2 in the back of your manual, use the
standard DA Form 2028 (Recommended Changes to Publications and Blank
Forms) and forward to the Commander, US Army Communications and Elec­tronics Materiel Readiness Command, ATTN: DRSEL-ME-MQ, Fort Mon­mouth, NJ 07703.

In either case a reply will be furnished direct to you.

This manual is an authentication of the manufacturer’s commercial literature which, through usage, has been
found to cover the data required to operate and maintain this equipment. Since the manual was not prepared
in accordance with military specifications, the format has not been structured to consider levels of main­tenance.

Change 1 i

TM 11-6625-2820-14&P

SECTION

0 INTRODUCTION . . . . . . . . . . . . . . . . .

I GENERAL INFORMATION . . . . . . . .

1-1.

Introduction . . . . . . . . . . . . . . . .

1-6.

Supplementary Instruments . .

Instrument Options . . . . . . . . . .

1-9.

1-11. Instrument Identification. . . . .

1-13. Klystron Warranty Claim Sheet

II INSTALLATION . . . . . . . . . . . . . . . . . .

2-1. Incoming Inspection. . . . . . . . . .

Installation . . . . . . . . . . . . . . . . .

2-3.
2-6. Conversion to Rack Mount. . .
2-7.
2-9.

Air Filter Inspection . . . . . . . .

Power Requirement . . . . . . . . . .

2-11. Three Conductor Power Cable. .

2-14. Repackaging for Shipment . . . .

III OPERATION . . . . . . . . . . . . . . . . . . . . .

3-1. Introduction . . . . . . . . . . . . . . . .

3-3. Controls and Indicators . . . . . . .

3-5. Operating Procedures. . . . . . . . .

3-7.

Stabilized Source . . . . . . . . . . . . .

IV PRINCIPLES OF OPERATION . . . . .

4-1. Introduction . . . . . . . . . . . . . . . .

4-3. RF Oscillator . . . . . . . . . . . . . . . .

4-6. Pin Diode Modulator . . . . . . . . .

4-16. Modulation Circuits. . . . . . . . . .

4-18.
4-20.
4-22.
4-25.

ExternalPulse . . . . . . . . . . . .

Internal Square Wave. . . . . . .

Extemal AM . . . . . . . . . . . . . .

Internal Meter and Automatic

Level Control (ALC) . . . . . . . .

4-36. External Leveling . . . . . . . . . .

4-37. Regulated Power Supply. . . . . .

V MAINTENANCE . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . .

5-1.

Test Instruments Required. . . .

5-3.

Periodic Maintenance. . . . . . . . .

5-5.
5-6.

Cleaning the Air Filter . . . . . .

5-8. General Maintenance . . . . . . .

5-10.

Cover Removal . . . . . . . . . . . .

6-12. Troubleshooting. . . . . . . . . . . . .

5-14. Repair . . . . . . . . . . . . . . . . . . . . .

6-16. Klystron Removal and

Replacement . . . . . . . . . . . . . .

6-17.
6-18.
6-19.

Tube Removal . . . . . .. o.....

Tube Replacement . . . . . . . . .

RF Probe Removal and

Replacement . . . . . . . . . . . . .

6-20.
6-21.
6-22.

Probe Assembly Removal . . .

Probe Replacement. . . . . . . . .

Pin Modulator Removal and

Replacement . . . . . . . . . . . . . . . .

5-23.

5-25.
6-26
5-27.

Modulator Removal . . . . . . . .

Modulator Replacement. . . . .

Calibration . . . . . . . . . . . . . . . . .

Regulated Power-Supply

Adjustment . . . . . . . . . . . . . . .

6-28.

Frequency Tracking,

preliminary. . . . . . . . . . . . . . .

6-29.

Power Adjustment . . . . . . . . .

Page

0-1

1-1
1-1
1-1

1-1

1-1

1-1
2-1

2-1
2-1
2-1
2-1
2-1
2-1
2-1

3-1
3-1
3-1
3-1
3-1

4-1
4-1
4-1
4-1
4-3
4-3
4-3
4-4

4-5
4-6
4-6

5-1
6-1
5-1
5-1
6-1

6-1
5-1
6-1
5-6

5-6
6-6
6-6

5-6
5-6
6-7

5-9
5-9
5-9
6-9

6-9

5-10
5-10

Illus

Figure

S

ECTION

6-30.

RF Power Output

Adjustment . . . . . . . . . . . . . . .

5-31. Meter Amplifier . . . . . . . . . . .

5-32. Frequency Tracking, Final . . . .

6-33.
5-34.
5-35.

ALC Amplifier . . . . . . . . . . . . .

Pulse Modulation Adjust. . . .

Square-Wave Adjust . . . . . . .

5-35A. AM Adjust . . . . . . . . . . . . . . . . .

6-36. Performance Checks. . . . . . . . . .

5-38. Frequency Range and

Accuracy . . . . . . . . . . . . . . . . .

5-39. AFControl Check . . . . . . . . . .

5-40.
5-41.
6-42.
6-43.

Power Output Check. ., . . . . .

Leveled Output Check . . . . . .

Pin Diode On-Off Ratio. . . . . .

Internal Square-Wave

Check . . . . . . . . . . . . . . . . . . . .

5-44.

5-45.

External Pulse Check . . . . . . .

External AM Check . . . . . . . .

5-46. Measurement of Residual and

Incidental FM . . . . . . . . . . . . .

6-47. Cam Cable Replacement . . . . . . .

5-48.
5-49.

Tools Required . . . . . . . . . . . .

Procedure . . . . . . . . . . . . . . . .

5-51. Low Pass Filter Replacement . .
5-52.

Tools Required . . . . . . . . . . . .

5-63. Procedure . . . . . . . . . . . . . . . .

5-65. Cavity Wiper Replacement . . . .

5-57.
5-59.

Parts Required . . . . . . . . . . . .

Replacement Procedure . . . . .

5-60. Frequency Drive Gear

Replacement . . . . . . . . . . . .

VI REPLACEABLE PARTS . . . . . . . . . . .

6-1.

Introduction . . . . . . . . . . . . . . . .

6-3.

Abbreviations . . . . . . . . . . . . . . .

6-5.

Replaceable Parts List. . . . . . . .

6-7.

APP

ENDIX

Ordering Instructions . . . . . . . .

0 REFERENCES . . . . . . . . . . . . . . ..D

I MANUAL CHANGES . . . . . . . . . . . . . .

SECTION

I-1.

Introduction . . . . . . . . . . . . . . . .

I-3.

Manual Changes . . . . . . . . . . . . .

I-6

Manual Changes Instructions . .

PPENDIX

A

II Illustrated Parts Identification . . . .

III MAINTENANCE ALLOCATION ... .

IV. ORGANIZATIONAL. DIRECT SUP-

PORT, AND GENERAL SUPPORT
MAINTENANCE REPAIR
PARTS AND SPECIAL

TOOLS LIST
(INCLUDING DEPOT
MAINTENANCE REPAIR
PARTS AND SPECIAL
TOOLS)

SECTION

I Introduction . . . . . . . . . . . . . . . . . . . . . .

II Repair Parts List . . . . . . . . . . . . . . . . . . .

Group

00 Signal Generator

SC 735/URM-165 . . . . . . . . . . . . . . . . .

Page Figure

Illus

6-10
5-12
5-12
5-13
5-14

5-14

5-14
5-14

5-14
5-14
5-15
5-15
5-15

5-15
5-17
5-17

5-18
5-18
5-18
5-18
5-21
5-21
5-21
6-21
5-21
5-21

5-24

6-1
6-1
6-1
6-1

6-1

0-1

i-1

i-1
i-1
i-3

ii- 1

III-1

IV-1
IV-6

IV-5

1

ii

Change 1

TM 11-6625-2820-14&P

SECTION

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . .

HighVoltagePower Supply . . . . . . . . . .

Control Panel . . . . . . . . . . . . . . . . . . . . . .

Leveler Assembly . . . . . . . . . . . . . . . . . .

Low Pass FilterAssembly . . . . . . . . . . .

01 Circuit Card Assembly,

HighVoltagePower

Supply A100 . . . . . . . . . . . . . . . . . . . . .

02 Circuit Card Assembly,

Low Voltage and

Figure
1-1,
2-1.
3-1.

3-2.

3-3.

3-4.
3-5.
3-6.
3-7.
3-8.
4-1.
4-2.

4-3.
4-4.
4-5.
4-6.
4-7.
4-8.
4-9.
5-1.

5-2.
5-3.

5-4.
5-5.
5-6.
5-7.
5-8.
6-9.
5-10.

Table

1-1.
5-1.
5-2.
5-3.
5-4.
5-5.
5-6.

Mode 18616A SignalGenerator . . . . . . . . . . .

Conversion to RackMount . . . . . . . . . . . . . . .

Front and Rear Panel Controls

and Indicators . . . . . . . . . . . . . . . . . . . . . . .

Unleveled RF Power Output . . . . . . . . . . . . . .

Internally-Leveled RFOutput . . . . . . . . . . . .

Externally-Leveled RF Output . . . . . . . . . . . .

Internal Square-Wave Modulation . . . . . . . . .

External Pulse Modulation . . . . . . . . . . . . . . .

External FM Modulation...... . . . . . . . . . .

External AM Modulation...... . . . . . . . . . .

Circuit Block Diagram . . . . . . . . . . . . . . . . . .

Simplified Block Diagram of PIN

Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RF Attenuator Unit . . . . . . . . . . . . . . . . . . . .

ALC Attenuator Unit . . . . . . . . . . . . . . . . . . .

Pulse ModulationCircuit . . . . . . . . . . . . . . . .

SquareWaveModulation Circuit . . . . . . . . . .

External AM Circuit . . . . . . . . . . . . . . . . . .

ALC and Meter Circuit . . . . . . . . . . . . . . . . . .

Series-RegulatedPower Supply . . . . . . . . . . .

Model 8616ABlock Diagram.. . . . . . . . . . . .

Cut-Away View of Klystron Cavity

and Klystron Assembly . . . . . . . . . . . . . . . .

RF Probe Assembly . . . . . . . . . . . . . . . . . . . .

PIN Modulator (Extemal View) . . . . . . . . . . .

Frequency Tracking Setup . . . . . . . . . . . . . . .

Frequency Tracking . . . . . . . . . . . . . . . . . . . .

Frequency and Power Measurement. . . . . . .

Internal Square Wave Check . . . . . . . . . . . . .

External Pulse Check........ . . . . . . . . . . .

External AM Check . . . . . . . . . . . . . . . . . . . . .

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .

Test Equipment Required . . . . . . . . . . . . . . . .

Trouble Location . . . . . . . . . . . . . . . . . . . . . . .

Power SupplyAdjust . . . . . . . . . . . . . . . . . . .

Klystron Repeller Voltages . . . . . . . . . . . . . . .

Klystron Probe Adjust . . . . . . . . . . . . . . . . . .

ALC AmplifierAdjust . . . . . . . . . . . . . . . . . .

Illus
Page
IV-7
IV-9

IV-11
IV-15
IV-17

IV-19

Figure

7

ILLUSTRATIONS

Page

1-0

2-0
3-2

3-3
3-4
3-5
3-6
3-7
3-8
3-9
4-1

4-1
4-2
4-3

4-4
4-4
4-4
4-5
4-6
5-4

5-7

5-8

5-10
5-11
5-13
5-14
5-16
5-16
5-17

TABLES

Page

1-0

5-2
5-5
5-5

5-10
5-12
5-12

2
3
4
5
6

SECTION

ALC A500 . . . . . . . . . . . . . . . . . . . . . . . IV-23

03 Cavity Assembly . . . . . . . . . . . . . . . . . . . IV-27

04 Probe Assembly (No parts authorized)

SECTION

III Special Tools List

(Nonapplicable)

IV National Stock Number

and Part Number Index. . . . . . . . . . .

Figure
5-11.

5-12.
5-13.

5-14.

5-15.
5-16.
5-17.
5-18.
5-19.
5-20.
5-21.
A-1.
A-2.

B-1.

B-2.
B-3.
B-4.
B-5.

B-6.
B-7.
B-8.

Table

6-1.
6-2.
6-3.
A-1.
A-2.
A-3.

Top View, Cover Removed . . . . . . . . . . . . . . .

Residualand IncidentalFMChwk . . . . . . . .

ExplodedView-CamAsmmbly . . . . . . . . . . .

Low Pass FilterAsaembly Drawing . . . . . . . .

FormingtheCenter Conductor Fingers . . . . .

Modulation and Klystron Circuits . . . . . . . . .

ALCBoard (A500) . . . . . . . . . . . . . . . . . . . . . .

ALCCircuit . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regulated +20Voltand Filament Supplies .

HighVoltageBoard(A100). . . . . . . . . . . . . . .

HighVoltagePower Supply . . . . . . . . . . . . . .

High VoltageBoard (A100). . . . . . . . . . . . . . .

Partial Schematic of Figure 5-17

ALC Circuit (Part of Change D) .......

HP Mode1 8616A, Signal Generator,

Generator Arrangement . . . . . . . . . . . . . . .

HP Model 8616A, Signal Generator,

Control Panel . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Cavity Assembly . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Probe Assembly . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

High Voltage Power Supply

Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Leveler Chassis . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Cabinet Assembly . . . . . . . . . . . . . . . . . . .

Reference Designations and Abbreviations .

Replaceable Parts . . . . . . . . . . . . . . . . . . . . . .

Manufacturers Code List . . . . . . . . . . . . . . . .

Manual Changes by Serial Number . . . . . . . .

Manual Changes by Assembly . . . . . . . . . . . .

8616A Recommended Changes . . . . . . . . . . .

Page

IV-28

Illus
Figure

8
9

Page

5-19
5-20
5-20
5-22
5-24
5-27
5-29
5-29
5-31
5-33

5-33

i-4
i-6

ii- 3
ii-5
ii- 7
ii-9

ii-11

ii-13
ii-15

ii-17

Page

6-2
6-4
6-9

i-2
i-2
i-7

Change 1 iii

TM 11-6625-2820-14&P

Figure 1-1. Model 8616A Signal Generator

Table 1-1. Specifications

Frequency Range:

4500 MHz.

Vernier:

MHz for fine tuning.

Frequency Calibration Accuracy:
Frequency Stability:

ambient temperature, less than 2500 Hz peak residual

FM, in a 10 kHz bandwidth, negligible incidental FM
in pulse and AM operation for attenuator settings be­low —10 dB. 0.003% change for line voltage variation
of ±10%.

RF output power:

3000 to 4500 MHz into a 50 load. Output attenua­tion dial directly calibrated in dBm from 0 to –127

dBm. A second uncalibrated output (approximately

0.5 mW) is provided on the front panel.

RF Output Power Accuracy (with respect to attenuation

dial:
Attenuator Accuracy:

–10 to –127 dBm: ±2 dB ±.06 dB/10 dB.

Leveled Output:

attenuation setting below 0 dB; ±l.0 dB.

Internal Impedance:

Modulation:

pulse.

Internal Square Wave:

cies available on special order.

External Pulse:

to +100V peak input.

F control has a range of approximately 1.5

±1.0 dB + attenuator accuracy (0 to –127 dBm).

direct reading within 2 MHz 1800 to

±10 MHz.

Approx. 0.005%/°C change in

+10 dBm (10 mW) +3 dBm from

for attenuation dial settings of

over entire frequency range at any

500; SWR less than 2.0.

On-off ratio at least 20 dB for square wave,

950 to 1050 Hz. Other frequen-

50 Hz to 50 kHz; 2 µsec rise time max +20

External AM:
External FM:

a. Front panel connector capacity-coupled to repeller

of klystron.

b. Four terminal rear panel connector (CinchJones

type S304AB) is DC-coupled to repeller of klystron.

Mode width between 3 dB points varies as follows: from

minimum of about 4 MHz to 5.5 MHz between 1800
and 3000 MHz to a maximum of about 8.5 MHz be­tween 3000 and 4500 MHz; klystron sensitivities are

about 100, 50, 200 and 100 kHz/V, respectively.

Power Source:

imately 125W.

Dimensions:

Weight:

DC to 1 MHz.

115 or 230V ±l0%, 50 to 60 Hz, approx-

net 48 lb. (22 kg).

1-0

Change 2

SECTION I

GENERAL INFORMATION

TM 11-6625-2820-l4&P

1-1. INTRODUCTION

1-2. The Model 8616A Signal Generator provides

RF power in the 1800- to 4500-MHz range. The
instrument produces an RF power output of at
least 2 mW. Output frequency and attenuation are
read directly on digital dials, and fine frequent y
changes can be made by means of the front-panel
A F control. Complete specifications are given in
Table 1-1. The 8616A is shown in Figure 1-1.

1-3. The instrument has two power output con-

nectors which supply RF power simultaneous y.
One output provides at least 10 mW (2 mW from

3000 to 4500 MHz) of power and may be leveled.

When in the leveled output mode of operation and
the output is 0 dBm or less, the RF output is held
quite constant across the band without resetting
the attenuator or power monitor. The other output
connector provides an uncalibrated output of at
least 0.5 mW. A wave-guide-beyond-cutoff attenua­tor, which is referenced to the RF output, accu­rately attenuates the calibrated RF power output
from O to –127 dBm.

1-4. RF power output can be internally square­wave modulated. In addition, the RF power can be
externally AM, FM, or pulse modulated. An exter­nal ALC (automatic level control) input which can
be used for remote leveling loop control and an

external DC-coupled FM input which can be used
for external AFC is also provided.

1-5. PIN diode attenuators are used for leveling,
square wave, pulse, and amplitude modulation. The
PIN attenuator is an absorption device that can be

electrically controlled to attenuate RF power. A
sampling loop which includes a PIN diode attenua­tor compensates for changes in RF power output
to hold the RF power output nearly constant.

1-6. SUPPLEMENTARY INSTRUMENTS

1-7. Two instruments capable of extending the
operating parameters
8403A and the Model 2650A. The Model 8403A
Modulator produces output pulses with 30 to 40

of the generator are the

nanosecond rise and decay time characteristics.
Pulse outputs are accurately variable in frequency,
width, and delay. Amplitude modulation is avail­able with frequency responses to 10 MHz for sine
waves. Square-wave frequency capability is accu­rately available. The modulator also provides sync
and delayed-sync outputs.

1-8. The Model 2650A Oscillator Synchronizer
may be used directly to stabilize all internal cavity
reflex klystron signal generators. Short-term sta­bility is one part in 108/sec, and long-term stability
is one part in 106/week over 0 to 50 degrees
centigrade.

1-9. INSTRUMENT OPTIONS

1-10. In addition to the standard instrument, the
option 01 is available. The option 01 instrument
has its input connectors located on both the front
and rear panel and its output connectors located
on, the rear panel; in all other respects it is the same
as the regular signal generator.

1-11. INSTRUMENT IDENTIFICATION

1-12, Hewlett-Packard uses a ten digit serial num­ber (on instrument rear panel) to identify instru­ments. The first four numbers and letter are the
serial prefix number and the last five digits are

unique to a specific instrument. If the serial prefix
on your instrument does not appear on the title
page of this manual, there are differences between
the manual and your instrument which are de­scribed in a Manual Change sheet included with the

manual. If the change sheet is missing, it may be

obtained, on request, from your nearest Hewlett-

Packard office.

1-13. KLYSTRON WARRANTY CLAIM SHEET

1-14. The klystron

klystrons purchased
guaranteed as set forth in the CONDITIONS OF
WARRANTY FOR KLYSTRON TUBES which is

found on the next to last page of this manual.

supplied and replacement

from Hewlett-Packard are

1-1

TM 11-6625-2820-14&P

2-0

Figure 2-1. Conversion to Rack Mount

SECTION II

INSTALLATION

TM 11-6625-2820-14&P

2-1.

INCOMING INSPECTION

2-2.

This instrument was inspected both mechani-

cally

and electrically before shipment. To confirm

this,

the instrument should be inspected for physi-

cal damage in transit.
accessories, and test the electrical performance of
the instrument, using the procedure outlined in
Paragraph 5-36. If there is damage or deficiency,
see the warranty on the inside rear cover of this
manual.

2-3. INSTALLATION

2-4. The Model 8616A is delivered as a cabinet
mount instrument. A kit is supplied with the

instrument for conversion from cabinet to rack
mount.

2-5. Whether the instrument is cabinet- or rack-

mounted, provision should be made for adequate
circulation of air around the instrument. The in­strument cooling fan is located at the rear of the
instrument and louvers are located on instrument
side panels. Proper air circulation is most impor-

tant at the sides and rear of the instrument.

IF FAN IS NOT OPERATING, THE
INSTRUMENT SHOULD NOT BE
OPERATED.

2-6. Conversion to Rack Mount

a.

Remove trim strip on sides of instrument

(refer to Figure 2-1).

Also check for supplied

2-7. Air Filter Inspection

2-8. The Model 8616A uses forced-air cooling to
maintain tolerable temperature within the instru­ment. Incoming air is filtered through a special

filter at the rear of the instrument. The air filter
should be checked periodically and if dirty,
cleaned. Refer to Paragraph 5-6 for air filter main­tenance.

2-9. POWER REQUIREMENT

2-10. The Model 8616A can be operated from a
115 or 230V, 50 to 60 Hz source. A two-position
slide switch (LINE VOLTAGE ) at the rear of the
instrument selects AC operation mode. The line

voltage at which the instrument is set to operate
appears on the slider of the switch. A 2 ampere
standard fuse is used for 115V operation; a 1
ampere standard fuse is used for 230V operation.

2-11. THREE-CONDUCTOR POWER CABLE

2-12. To protect operating personnel, the National
Electrical Manufacturer’s Association (NEMA)

recommends that the instrument panel and cabinet

be grounded. This instrument is equipped with a
three-conductor power cable which, when plugged
into an appropriate receptacle, grounds the instru­ment. The offset pin on the power cable three­prong connector is the ground wire.

2-13. The protection provided by grounding the
instrument cabinet may be lost if any power cable
other than the three-pronged type is used to couple
the ac line voltage to the instrument.

b. Remove tilt stand by pressing two sides of
stand toward center of instrument and lifting it
out.

c. Remove five feet at bottom of instru­ment. Press button in center of each foot, slide
them toward center of instrument, and lift out.

d. Place rack mounting flanges (two) where

trim strips were and secure with screws provided.

e.

Add filler strip to bottom of instrument.

f.

Rack mounting under
conditions must be supplemented with additional
support at rear.

severe vibration

2-14. REPACKAGING FOR SHIPMENT

2-15. The following list is a general guide for
repackaging an instrument for shipment. However,
if you have any questions, contact your local HP
field office.

If possible, use the original container de-

a.

signed for the instrument. If a carton and packing

materials are desired, they can be ordered from
your local HP field office.

b. The instrument is supported by four poly-

ethylene supports fitted to the instrument height:

one support located at each corner.

2-1

TM 11-6625-2820-14&P

NOTE

If the instrument is to reshipped to the
Hewlett-Packard Company for service or
repair, attach to the instrument a tag
identifying the instrument by owner,

model, and full serial number, and indi­cating the service or repair to be accom­plished. In any correspondence, refer to
the instrument by model number and
complete serial number.

2-2

SECTION Ill

OPERATION

TM 11-6625-2820-14&P

3-1. INTRODUCTION

3-2. The Model 8616A can provide 1.0 mW of
leveled power across its frequency range (RF out­puts leveled to within ±1.0 dB can be obtained
across the band for attenuator setting of 0 dB or
less). Output power can be attenuated to –127 dB.
When operating unleveled, attenuation reference is

the klystron power output; when operating leveled,
attenuation reference is output reference setting.
Internal square-wave modulation is available from
950 to 1050 Hz. External FM, AM, and pulse
modulation voltages also can be used. Two or three
modulation modes of operation can be applied to
the instrument simultaneously; push-button con­trols select the mode of operation. External modu­lation signal inputs are located directly below the
modulation to which they apply.

RF power in excess of approximately

125 mW should never be applied to RF
power output
damage could result.

3-3. CONTROLS AND INDICATORS

3-4. Front and rear panel controls and connectors
are shown in Figure 3-1. Each control and connec­tor is identified with a numbered call-out, and an
explanation of the function, given in the accom­panying text, is keyed to the call-out number.

connectors as internal

3-5. OPERATING PROCEDURES

3-6. The operating procedures Figures 3-2 through
3-8) give step-by-step procedures for the various
modes of operation.
obtaining the following leveled and unleveled out­puts: CW, square-wave modulated (modulating
voltage supplied internally, and FM, AM, and
pulse-modulated (modulating voltage supplied
externally ). Steps of each procedure are numbered
according to the sequence in which they are to be
performed, and any control or connector used is
identified with the number of the step in which it
is used.

3-7. STABILIZED SOURCE

3-8. To use an 2650A Oscillator Synchronizer
with the Signal Generator, proceed as follows:

The rear panel connector EXT FM (J201)

a.
is a Cinch-Jones type S304AB. Connection be­tween this jack and J5 of the 2650A must be made
as follows:

Pin 3, J201, to Pin E, J5, 2650A
Pin 4, J201, to Pin F, J5, 2650A
Pin 1, J201, to Pin G, J5, 2650A
Pin 2, J201, no connection

Connect RF output from UNCAL

b.
OUTPUT connector on Model 8616A to OSCIL­LATOR INPUT connector on Model 2650A. De­press EXTERNAL FM button on Model 8616A
and proceed as explained in the instruction manual
for the Model 2650.

Instructions are given for

3-1

TM 11-6625-2820-14&P

1.

LINE. Connects primary power to instrument;

lamp glows.

RF. Applies power to RF POWER OUTPUTS.

2.

ATTENUATION (dB). Sets RF power level at

3.
CAL RF POWER OUTPUT.

4.

UNCAL RF POWER OUTPUT.

mately 0.5 mW unleveled and unattenuated RF

power.

FREQUENCY (MHz). Sets

5.

F. Permits small deviations from FREQUENCY

6.
setting (±1.5 MHz).

ZERO SET. Adjust for zero indication on dBM

7.

meter (with RF turned off).
ALC. Levels calibrated RF output; used to set a

8.
reference on dBm meter.

INTERNAL SQ WAVE.

9.
PUT. SQ WAVE control adjusts modulation fre­quency.

Modulates CAL RF OUT-

Provides approxi-

RF frequency.

EXTERNAL PULSE.

10.
pulse input will provide modulation voltages re-

quired to pulse modulate CAL RF OUTPUT.
Positive pulses turn RF “ON

11.

EXTERNAL FM. AC

FM input will provide frequency modulation of
both CAL and UNCAL outputs.

12.

EXTERNAL AM.

input will provide modulation voltages required to
AM modulate CAL RF OUTPUT.

13.

INPUT REMOTE LEVELING. Input jack for

external leveling loop voltage applied to level
generator CAL RF POWER OUTPUT.

14.

LINE. Male receptacle which connects to the

power cord.

LINE VOLTAGE. Arranges input power trans-

15.
former to accept either 115 or 230 volt, 50 to 60
Hz primary power input.

16.

OPTION 01.

on rear panel (input connectors also located on
front panel).

17.

EXT FM:

lystron for stabilization of output frequency.

Input and output connectors located

Four terminal connector DC-coupled to

Positive pulses to external

voltages applied to external

Signals applied to external AM

3-2

Figure 3-1. Front and Rear Panel Controls and Indicators

TM 11-6625-2820-14&P

Depress LINE; lamp glows,

1.
Note meter pointer on dBm meter.

2.
Depress RF; there should be some deflection of dBm meter pointer.

3.

When RF button is depressed, meter pointer will fluctuate from
approximately +1 dBm at low frequency to +4 dBm or more at high
frequency.

4.

Set FREQUENCY (MHz) to desired frequency.
The ATTENUATION (dB) knob will attenuate RF power at CAL RF POWER OUTPUT.

5.
Take unleveled but attenuable RF power at CAL RF POWER OUTPUT.

6.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

7.

8.

Use A F control when a small deviation from FREQUENCY (MHz) setting is desired.

F control should be centered when not in use.

indicating heater and high voltage are applied.

NOTE

NOTE

Figure 3-2. Unleveled RF Power Output

3-3

TM 11-6625-2820-14&P

1.

Depress LINE.
Check that meter pointer on dBm meter is on ZERO SET mark; if not, adjust accordingly.

2.

Depress RF and INTERNAL ALC; there should be some deflection of dBm meter pointer.

3.

4.

Set FREQUENCY (MHz) low frequency.

Adjust ALC CAL OUTPUT control for desired dBm reference on dBm meter. The ALC system

5.

holds RF output power across the band to within ±1.0 dB for levels of 0 dBm or less. The
most common reference used is —10 dBm because the attenuated RF output power can be read
directly from attenuator readout. Leveled RF output power can be obtained across the band;
however, ATTENUATION (dB) will not accurately calibrate above –10 dBm.

NOTE

Power may be leveled above 0 dBm over that portion of the band where
the desired power is available.

6.

Set ATTENUATION (dB) to desired attenuation. The RF power level at CAL RF POWER
OUTPUT is the algebraic sum of the dBm meter setting and of the ATTENUATION (dB)
setting.

Take leveled and attenuable RF power available at CAL RF POWER OUTPUT.

7.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

8.

9.

Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

3-4

Figure 3-3. Internally-Leveled RF Output

TM 11-6625-2820-14&P

Depress LINE.

1.
Check that meter pointer on dBm meter is on ZERO SET mark.

2.
Depress RF and INTERNAL ALC.

3.
Set FREQUENCY for 1800 MHz.

4.
With a directional coupler connected between CAL output and the load, and as close to the

5.
load as possible, sample and detect incident power and apply the detected signal to INPUT
REMOTE LEVELING phone jack connection (rear panel). Approximately 40 mV but not
more than 240 mV is necessary.

Adjust ALC CAL OUTPUT for desired reference on dBm meter. This reference point may vary

6.
from that used with internal leveling due to different detector sensitivities.

Adjust ATTENUATION (dB) for desired attenuation.

7.
unless a 0 dBm reference has been set while monitoring with a power meter.

Take leveled and attenuable RF power available at CAL RF POWER OUTPUT.

8.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

9.
Use F control when a small deviation horn FREQUENCY (MHz) setting is desired.

10.

The attenuator is not direct reading

Figure 3-4. Externally-Leveled RF Power

3-5

TM 11-6625-2820-14&P

1. Depress LINE.

NOTE

When unleveled power is to be modulated, omit steps 2, 5 and 6.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter.

7. Set ATTENUATION dB.

8. Depress SQ. WAVE.

9. Adjust SQ WAVE for desired modulation frequency.

10. Take leveled and attenuable RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY MHz setting is desired.

NOTE

F control should be centered when not in use.

3-6

Figure 3-5. Internal Square- Wave Modulation

TM 11-6625-2820-14&P

1. Depress LINE.

NOTE

If external pulse modulation of unleveled power is desired, omit steps 2,
5and6.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter.

7. Set ATTENUATION (dB) as desired.

8. Depress EXTERNAL PULSE.

9. Apply +20 to +100V 50 Hz to 50 kHz positive pulse modulating signal to EXTERNAL PULSE
INPUT.

10. Take leveled and attenuable pulse modulated RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

Figure 3-6. External Pulse Modulation

3-7

TM 11-6625-2820-14&P

Depress LINE.

1.

If external FM modulation of unleveled power is desired, omit steps 2, 5, and 6.

NOTE

Check that meter pointer on dBm meter is on ZERO SET mark.

2.
Depress RF.

3.
Set FREQUENCY (MHz).

4.
Depress INTERNAL (ALC).

5.
Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter. The ALC system holds

6.
the RF output power across the band to within limits at frequencies up to 1 kHz provided the
FM voltages are small enough to maintain operation in the center of the mode. The most

common reference used is —10 dBm because the attenuator RF output power can be read
directly from attenuator readout.

NOTE

Power may be leveled above 0 dBm over that portion of the band where the desired power is available.

Set ATTENUATION (dB).

7.
Depress EXTERNAL FM.

8.
Apply modulating signal to EXTERNAL FM INPUT (front or rear panel).

9.
Take leveled and attenuable frequency modulated RF power output at CAL RF POWER

10.
OUTPUT.

Take unleveled FM-modulated RF power at UNCAL RF POWER OUTPUT.

11.
F control should be centered so that the klystron will operate in the center of the mode.

12.

3-8

Figure 3-7. External FM Modulation

TM 11-6625-2$20-14&P

1. Depress LINE.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

NOTE

If AM modulation of unleveled power is desired, omit steps 5 and 6 and
proceed to step 7. Also, unleveled power can be AM-modulated with a

dc coupled audio signal.

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT control for at least 3 dB of attenuation. Due to leveIing at the
frequency desired, the ALC system holds the RF output power across the band to within limits
except for variations due to an AM signal. The most common reference used is —3 dBm because
this allows AM signal to modulate the RF above (3 dB) this level.

7. Set ATTENUATION (dB).

8. Depress EXTERNAL AM.

9. Apply AM modulating signal to EXTERNAL AM INPUT (6 volts peak-to-peak).

10. Take AM-modulated and attenuable RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

NOTE

F control should be centered when not in use.

Figure 3-8. External AM Modulation

3-9/3-10

SECTION IV

PRINCIPLES OF OPERATION

TM 11-6625-2820-14&P

4-1. INTRODUCTION

4-2. Basically the intrument includes a RF
Oscillator, PIN Diode Modulator, Automatic Level­ing Circuit, Modulation Circuits, and Power Supply
as shown in Figure 4-1. The RF Oscillator is a

reflex klystron which always operates CW. The PIN

diode modulator is a current-controlled device that
attenuates RF power up to 20 dB or more. The
control circuits provide the modulation currents

required by the PIN modulator. The power supply

provides the regulated dc voltages required to
operate the circuits in the instrument.

4-3. RF OSCILLATOR

4-4. The RF Oscillator, which generates the RF
power, consists of a velocity-modulated tube
operating in an external resonant cavity. The tube
is a reflex klystron operating in the 1-3/4 and 2-3/4
modes.

4-5. The RF power output from the oscillator,
which may be CW or CW with FM, is obtained
from the resonant cavity by means of pickup
probes located in

which open into the resonant cavity. One of these

probes delivers RF power directly to the UNCALI­BRATED RF OUTPUT connector, the other two

deliver RF power to the PIN modulator.

small sections of waveguide

4-6. PIN DIODE MODULATOR

4-7. The PIN modulator, which is two nearly
identical units in one, is a high-speed, current­controlled absorption-type attenuator. One unit,
the RF attenuator unit, is shown in Figure 4-3. The
second unit, the ALC attenuator unit, is shown in
Figure 4-4. It is a comparison unit. A simplified
illustration of the modulator is shown in Figure
4-2. Each PIN diode unit includes a transmission
line, PIN diodes, low-pass filter, and high-pass
filters.

Figure 4-2. Simplified Block Diagram

of PIN Modulator

Figure 4-1. Circuit Block Diagram

4-8. The PIN diode is a slice of nearly Pure silicon
wafer in which the P and N traces are nearly equal.
P-type impurities are diffused from one side into
the wafer, and N-type impurities are diffused from
the other side, leaving a layer of intrinsic semi­conductor (silicon) through the middle. Thus the
name, PIN diode. At frequencies below 100 MHz
the PIN diode rectifies the same as any other good

junction diode. However, at frequencies above 100

MHz, rectification efficiency drops rapidly because
of carrier storage in the intrinsic (I) layer.

4-9. When forward-bias current flows through the
PIN diode, holes and electrons are stored in the I
layer. The more the bias current, the larger the
amount of stored charge-carriers. When reverse bias
is applied, reverse current flows until the stored
carriers are depleted. During this period, the diode
impedance remains 10 w. Currents above several
hundred megacycles do not flow in the reverse
direction for a long enough time to remove those
charge carriers.

So, microwave currents

do not

4-1

TM 11-6625-2820-14&P

Figure 4-3. RF Attenuator Unit

significantly change the instantaneous amount of
charge carriers stored, and there is negligible recti­fication.

4-10. There is, however, a resistance to microwave
current flow. This resistance is inversely

proportional to the number of charge carriers
stored in the I layer, and the number of charge
carriers, in turn, is proportional to the forward bias
current. By varying the bias on a diode from back
bias (no stored charge) to about 1/2 mA forward
bias, the resistance to microwave currents varies
from approximately 5000 ohms to 30 ohms.

4-11. Pin Diodes Mounted in a Transmission

Line.

works, consider a PIN diode mounted across a

transmission line that has a characteristic impe­dance of 50 ohms. When the diode is back-biased
to about 5000 ohms, the microwave signal on the

transmission line is unattenuated because 5000

ohms compared to 50-ohm line impedance has

little effect. However, when the diode is

To understand how a PIN modulator

4-2

forward-biased to about 30 ohms, most of the

microwave current will flow through the 30-ohm
diode instead of propagating down the 50-ohm
transmission line. This current through the 30-ohm
diode represents microwave energy dissipated as
heat. Consequently the diode actually absorbs

microwave energy.

4-12. Figures 4-3A and 4-4A show the schematic

of the PIN diode modulator used in the Model

8616A. The PIN modulator contains seven PIN
diodes which are placed at approximately 1/4

wavelength along each strip transmission line. The

1/4 wavelength at midband spacing results in the
lowest average SWR because reflection from one
diode will tend to be absorbed and cancelled by

the adjacent diode. The resistance in series with the

diodes reduces voltage to the diodes and thereby

protects the circuit.

4-13. Modulation input in the form of diode bias

is used to change attenuation of the PIN diodes.

TM 11-6625-2820-14&P

Figure 4-4. ALC Attenuator Unit

Changes in diode bias produce changes in RF
output level.

4-14. Modulation circuits external to the PIN
modulator are protected by a low-pass filter (Fig-

ures 4-3 and 4-4 ) which prevents RF leakage.

Leakage, if present, could cause erratic action in
the circuits driving the PIN modulator and also
cause RF interference.

4-15. The high-pass filters (Figures 4-3 and 4-4)
permit RF energy to enter and leave the diode strip
line, while keeping the low frequency modulating
signals from entering the RF circuits preceding or
following the PIN modulator.

4-16. MODULATION CIRCUITS

4-17. The arrangement of the modulation circuits
depends on the mode of operation. Mode of
operation switching is accomplished by depressing
the appropriate front-panel button.

4-18. External Pulse

4-19. A simplified diagram of the circuits used in
the external pulse mode of operation is shown in
Figure 4-5. When the pulse button is depressed,
V401A is cut off, and V401B is conducting. The
conduction of V401 B draws current through the
PIN diodes in the REF attenuator unit; hence,
conduction of V401B forward biases the PIN
diodes causing the RF output to decrease by more
than 20 dB. A positive pulse applied to the exter-

nal pulse input turns V401A on, turns V401B off,
and allows RF power to pass through the PIN
diode attenuator with the RF output level clamped
to set level by CR403.

4-20. Internal Square Wave

4-21. A simplified diagram of the circuits used in
the internal square wave mode of operation is
shown in Figure 4-6. When V401B is conducting,
capacitor C402, is

discharging toward

4-3

TM 11-6625-2820-14&P

Figure 4-5. Pulse Modulation Circuit

approximately
cut off. When C402 discharges sufficiently, V401 A
begins to conduct and biases V401 B off through
the common cathode resistor R408. This results in
C402 charging toward approximately –225 volts as
long as V401A conducts. When C402 charges
sufficiently however, the current in V401A be­comes limited and V401B again conducts causing
V401A to cut off. The RC time constant of C402
is varied by R413, allowing frequency to be
changed from 950 to 1050 Hz. When V401B is
conducting the RF output is cut off by the PIN
diodes. The symmetry of the sqaure wave is ad-

justed by R410. R410 varies the voltage difference

across C402; by varying R410, the time for C402
to charge or discharge to a given potential is
controlled.

4-22. External AM

4-23. A simplified diagram

the external AM mode of

Figure 4-7. With the square

of operation off, V401B is cut off, causing con­duction of CR403 which isolates the square wave
and pulse circuit from the AM input and the PIN
diodes. Diode CR403 does this by clamping the

–200 volts while holding V401A

of the circuits used in

operation is shown in

wave and pulse modes

Figure 4-6. Square Wave Modulation Circuit

voltage at the junction of R414 and CR404 at
approximately +0.6 volt. This back biases CR404
providing the isolation.

Figure 4-7. External AM Circuit

4-4