Rdf products Dfa-1325b2 User manual

RDF PRODUCTS

17706 NE 72nd Street

Vancouver, Washington, USA 98682

Tel: +1-360-253-2181 Fax: +1-360-635-4615

E-Mail: [email protected]

Web Site: www.rdfproducts.com

OPERATOR'S MANUAL

DFA-1325B2 60-1,000 MHz FIXED-SITE

DIPOLE ADCOCK DF ANTENNA

Rev A03/07-15/dfa1325b2_opm_01

Original Writing: October 2013

WARNING

Please comply with the following basic rules of safety and common sense to ensure safe installation

and operation as well as long product service life:

1. LIGHTNING PROTECTION - Lightning strikes can cause death or serious injury to operating

personnel and destruction of equipment if appropriate precautions are not taken. It is essential

that the DFA-1325B2 be installed with the lightning protection precautions discussed in Section

V-G and Appendix C.

2. ELECTRICAL POWER LINES - Never install the DFA-1325B2 in the immediate vicinity of

electrical power lines. If the antenna comes in contact with power lines, death or serious injury

to operating personnel is likely to result. See Section V-H.

3. INSTALLATION ISSUES - The user must provide a mast mount for the DFA-1325B2 as

discussed in Section V. In addition, the user must securely guy the unit for maximum safety.

Please study Section V carefully and take all necessary steps to ensure that the DFA-1325B2

is safely mounted. If there is any doubt regarding the safety of the installation, obtain

professional help as required as per Section V-A.

4. ELECTROSTATIC DISCHARGE (ESD) ISSUES -AlthoughallRDF Products DFantennas and

DFprocessors are designed tominimizevulnerability toelectrostatic discharge (ESD) induced

damage, fixed-site DF systems are especially prone to this hazard. Do not connect the DFA-

1325B2 to the DF receiver/processor before studying and complying with the necessary system

grounding and procedural precautions discussed in Section V-I.

5. EXTERIOR WEATHER-SEALING - Sealants have been applied to the DFA-1325B2 exterior to

enhance weather-sealing and prevent water intrusion. For longest product service life, do not

break the integrity of these exterior weather-seals.

Check the RDF Products website at www.rdfproducts.com for updates and bulletins.

Can we improve this manual? Contact us at [email protected] to offer suggestions.

TABLE OF CONTENTS

SECTION I - GENERAL DESCRIPTION .................................................................. 1

SECTION II - SPECIFICATIONS .............................................................................. 3

SECTION III - PRE-ASSEMBLY INFORMATION .................................................... 5

A. UNPACKING AND INSPECTION ...................................................................... 5

B. EQUIPMENT SUPPLIED ................................................................................... 5

C. EQUIPMENT REQUIRED BUT NOT SUPPLIED .............................................. 6

SECTION IV - ASSEMBLY ....................................................................................... 7

A. INTRODUCTION ................................................................................................ 7

B. STEP-BY-STEP ASSEMBLY INSTRUCTIONS ................................................. 8

SECTION V - INSTALLATION ................................................................................. 13

A. GENERAL .......................................................................................................... 13

B. SELECTING A DF SITE ..................................................................................... 13

C. MOUNTING THE MAST SUPPORT PIPE ......................................................... 14

D. INSTALLING THE DFA-1325B2 ON THE MAST SUPPORT PIPE ................... 14

E. ORIENTATION ISSUES ..................................................................................... 16

F. SITE CALIBRATION .......................................................................................... 17

G. LIGHTNING PROTECTION ............................................................................... 19

H. ELECTRICAL POWER LINES ........................................................................... 19

I. ELECTROSTATIC DISCHARGE (ESD) ISSUES .............................................. 19

SECTION VI - MAINTENANCE ................................................................................ 21

SECTION VII - SIMPLIFIED THEORY OF OPERATION .......................................... 23

APPENDIX A - INTERFACE CABLE MATING CONNECTOR PIN-OUT ................. 25

APPENDIX B - INTERFACE CABLE EXTENSIONS ................................................ 26

APPENDIX C - MORE ON LIGHTNING PROTECTION ........................................... 28

iii

LIST OF ILLUSTRATIONS

Figure 1 - DFA-1325B2 60-1,000 MHz H/Sleeve-Dipole Adcock DF Antenna .. 1

Figure 2 - DFA-1325B2 Major Components ...................................................... 6

Figure 3 - DFA-1325B2 Hardware Close-Up ..................................................... 6

Figure 4 - Inserting the Cable into the Mast ...................................................... 8

Figure 5 - Installing the Mast Flange onto the Main Chassis ............................ 8

Figure 6 - UHF Sleeve-Dipole Array Installation ................................................ 9

Figure 7 - Turnbuckle Fastener Detail ............................................................... 9

Figure 8 - Kevlar Guy Tie-Down Detail .............................................................. 9

Figure 9 - Watson-Watt DF System Simplified Functional Block Diagram ........ 23

Figure 10 - Adcock DF Antenna Azimuthal Gain Patterns ................................... 24

Figure 11 - Interface Cable Mating Connector Pin-Outs ...................................... 25

iv

SECTION I - GENERAL DESCRIPTION

The RDF Products Model DFA-1325B2 is a dual-array VHF/UHF

H/sleeve-dipole Adcock single-channel radio direction finding

antenna covering 60-1,000 MHz in two bands. This rugged,

weather-sealed unit is specifically designed for permanent or

transportable fixed-site DF applications and is readily mast- or

tower-mounted.

BeingofatrueAdcockdesign,theDFA-1325B2avoidstheerratic

performance associated with inferior loop DF antennas and

provides sensitivity and listen-thru capability superior to that of

comparablepseudo-DopplerDF antennas. The DFA-1325B2 has

also been designed for high signal-handling capability for reliable

performance in dense signal environments. It is a particularly

goodchoicefortacticalmilitary,signalintelligence,andfrequency

managementapplicationswhereultra-widefrequencycoverageis

required.

The DFA-1325B2 has been specially designed so that its

performanceisindependent of itssupportingmastortower. (This

isaccomplished with the supplied isolation mast.) This is in sharp

contrast to competing mast-mounted DF antenna designs where

performance is adversely and unpredictably affected not only by

the presence of the mast, but also by changes in mast height.

The DFA-1325B2 directly interfaces with all RDF Products DF

receivers and bearing processors via a single 8-meter interface cable set (routed through the

isolation mast). Custom interface cables with user specified lengths are also available. The

aerialsareremovabletofacilitate storage, transport, and user testing. The isolation mast can

likewise be removed.

The DFA-1325B2 includes a digital “personality module” that reports model number and

frequency coverage information for this DF antenna. When connected to any of the RDF

Products“B”-seriesDFprocessors/receivers(e.g.,theDFP-1000B,DFP-1010B,DFR-1000B,

or DFR-1200B), the DFA-1325B2 automatically reports its model number and frequency

coverageinformation. Thisinformationisthendisplayedsothattheusercaneasilyavoidout-

of-band operation.

Figure 1 - DFA-1325B2 60-

1,000 MHz H/Sleeve-Dipole

Adcock DF Antenna

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NOTES

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SECTION II - SPECIFICATIONS

DF Technique: Single-channel 2-phase Adcock (mixed sense).

Frequency Coverage: 60-200/200-1,000 MHz continuous (two bands).

Bearing Accuracy: 3.0/5.0ERMS maximum; 2.5/4.0ERMS typical (V/UHF; ideal

siting conditions).

Polarization: Vertical.

Output Impedance: 50 ohms nominal.

2nd Order Intercept: +40/+28 dBm typical (V/UHF; referred to sense input).

3rd Order Intercept: +25/+13 dBm typical (V/UHF; referred to sense input).

Required X & Y Axis 1.0 volts p-p (+/-5%), sinusoidal (100-2000 Hz)

Encoding Tone Voltages:

Personality Module: Reports antenna model and frequency coverage information as

300N81 RS-232 data string “DFA-1325B-2, 60-200, 200-1000

<CR><LF>”.

Power Requirements: 11-16 VDC @ 300 mA (negative ground).

Operating Temperature: -40 to +60 degrees C.

Storage Temperature: -40 to +70 degrees C.

Humidity: 0-100%.

Maximum Wind Velocity: 80 mph.

Dimensions: 118.75"x20.75"x20.75"(HxWxD,including5'isolationmast,and

2' stainless-steel mast support pipe).

Weight: 63.5 lbs. (structural weight including main chassis, aerials,

isolation mast, and 8-meter interface cable; excluding 14 lbs.

stainless-steel mast support pipe and external guy lines).

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NOTES

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SECTION III - PRE-ASSEMBLY INFORMATION

A. UNPACKING AND INSPECTION

Carefully examine the shipping carton for damage before it is opened. If damage is evident,

have the carrier’s agent present, if possible, when the equipment is unpacked. If the carrier’s

agent cannot be present, retain the cartons and packing material for the carrier’s inspection

if the equipment is subsequently found to be damaged after unpacking.

Do not use knives or other sharp instruments to remove packing material from individual

items. To facilitate easy unpacking, the packing material protecting these individual items is

secured with easy-to-remove tape where possible.

To ensure that the shipment has been received complete, inventory all items against the

detailed shipping list. If a discrepancy is found, notify us immediately.

Theequipmentwasthoroughlyinspectedandfactoryadjustedforoptimumperformanceprior

to shipment and is ready for immediate use. If evidence of damage during shipment is found,

notify us immediately.

B. EQUIPMENT SUPPLIED

The following equipment is supplied:

1. Main chassis (P/N B325-6002; 1 ea., includes attached ferrite-loaded interface cable).

2. 200-1,000 MHz UHF sleeve-dipole array assembly (P/N S061-6103; 1 ea.).

3. Kevlar guy assemblies (P/N S061-6104; 4 ea., attached to P/N S061-6103 above).

4. DAB-053B aerials (P/N S024-0053; UHF, 5 ea.).

5. DAD-154B aerials (P/N S022-0154; VHF, 8 ea.).

6. 5' isolation mast (P/N S092-6005; 1 ea.).

7. 1.0" long 3/8" dia. 16 tpi stainless-steel anti-rotation bolts (P/N 605-009; 3 ea.).

8. 1.5" long 3/8" dia. 16 tpi stainless-steel bolts (P/N 605-022; 4 ea.).

9. DFA-1325B2 spare hardware kit (P/N B325-3002; 1 pack).

10. 2' long 3" inside-diameter schedule 40 unthreaded stainless-steel mast support pipe

(P/N S092-0002; 1 ea.).

11. Silicone sealant (P/N 701-012; 1 tube, partial).

12. DFA-1325B2 Operator’s Manual (P/N B325-9002; 1 ea.).

Note: Thetubeofsiliconesealantisnolonger. Incurrent-productionunits,allsealing is done

at the factory.

All of the above components are illustrated in Figures 2 and 3 below. Refer to these photos

asrequiredtoidentifythesecomponentsduringtheassemblyprocedurepresentedinSection

IV.

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Figure 2 - DFA-1325B2 Major Components

*Note: The 3 anti-rotation bolts (P/N 605-009) are pre-installed in the mast base*

C. EQUIPMENT REQUIRED BUT NOT SUPPLIED

The DFA-1325B2 must be used with an appropriate

RDF Products DF receiver/bearing processor. In

addition,asuitableuser-suppliedmastmountfittingmay

alsoberequiredtomounttheDFA-1325B2asdiscussed

inSectionV. The user must also supply non-conductive

guy lines and associated hardware. Finally, an

extension interface cable may be required if the

standard 8-meter interface cable is insufficiently long to

reach the DF receiver/bearing processor.

Figure 3 - DFA-1325B2 Hardware

Close-up

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SECTION IV - ASSEMBLY

A. INTRODUCTION

As mentioned, the DFA-1325B2 is shipped in disassembled form so that it can be stored and

transportedinacompactcontainer. Itisthereforenecessaryfortheusertoassemble the unit

prior to use. Although assembly is not difficult, it must be done carefully and in proper

sequence to avoid damaging the unit.

* CAUTION *

1. Two-Man Assembly - At least two people are required to properly

assemble and install the antenna.

2. Aerial Bending - Although the aerial rods are constructed of rugged

stainless steel, they can be bent by improper handling. Exercise

particular care during assembly not to place stress on these rods. Never

laydownthe antenna in suchafashionthat its weightissupportedbythe

aerials. Bentaerialswillreduceantennabearingaccuracy. Donotinstall

these aerials until the DFA-1325B2 is ready to be mounted atop its

supporting structure.

3. Ferrite-Loaded Cable - The cable attached to the main housing (see

Figure 2) is loaded with large ferrite cylinders. Since these ferrites are

somewhat brittle and can shatter, exercise caution when handling this

cable so as to prevent impact against hard surfaces or objects. Also, do

not attempt to bend this cable too tightly.

4. Main Chassis Integrity - The main chassis is a pre-assembled weather-

sealed unit. This housing contains no user-serviceable parts and should

never be opened. Disassembling the main housing without written

factory authorization voids the warranty.

5. Exterior Weather-Sealing - Sealants have been applied to the DFA-

1325B2exteriortoenhanceweather-sealingandpreventwaterintrusion.

For longest product service life, do not break the integrity of these

exterior weather-seals.

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B. STEP-BY-STEP ASSEMBLY INSTRUCTIONS

1. Locatethemain chassis (B325-6002)withits attachedferrite-loaded interface cable and

place it on a long table. ** WARNING **

All the DFA-1325B2 main chassis screws and bolts have been sealed

with RTV (silicone sealant) to prevent water intrusion. Do not attempt to

tighten, loosen, remove, or replace any of this hardware. Attempting to

do so will likely break the weather-seal and cause internal corrosion.

2. Orient the mast (S092-6005)

so that its upper flange (at the

top of the mast is facing the

main chassis (B325-6002)

underside as per Figure 4.

3. Push the ferrites along the

cable in the direction of the

main chassis so that these

ferrites are located along the

cable as far away as possible

from the two cable

connectors.

4. Insert the cable end (i.e., the

cable connectors) into the

hole in the mast flange (see

Figure 4) and then push the

cable (including the ferrites)

into the mast until the connectors exit from

the opposite mast end. If the cable binds

duringthisprocess,rollthe mast asrequired

tofree the cable. Ifthe cable connectorswill

not push through the opposite mast end,

finger-pull them through.

5. Attach the upper mast flange onto the main

chassis using four 1.5" long x 3/8" dia.

stainless-steel bolts (605-022). See Figure

5. Be sure to first wipe away any debris on

thechassis/flangematingsurfaces. Also,be

sure to push the ferrites as close to the main

chassis as possible so that the flange can

reach the chassis.Confirm that these bolts

are fully tightened and that the mast flange

is completely flush with the main chassis.

Figure 4 - Inserting the Cable into the Mast

Figure 5 - Installing the Mast Flange

onto the Main Chassis

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6. Do not install the four VHF aerials (S022-0154) at this time. Thesewill be installed when

the DFA-1325B2 is ready to be mounted atop is supporting structure.

7. Locate the UHF sleeve-dipole array assembly (S061-6103). In the following steps, this

assembly will be mounted on its mating connectors on the main chassis. These

connectors will then be tightened in sequence.

8. Inspect this assembly to see if one of the sleeve-dipoles is marked. If one of the dipoles

is marked, the assembly should be oriented so that so that the marked dipole is installed

on the “North” N-connector on the main chassis topside in the steps that follow. (The

“North” N-connector is the one corresponding to the position of the arrow label on the

main chassis topside.)

9. Thefollowingstepsandillustrationsarebasedonaverticalmastorientationforassembly

purposes. With this orientation, be sure that the bottom end of the mast does not crush

theexitingcables(i.e.,elevatethemastbottomoffthefloorslightlysothatthecablescan

exit freely).

10. Position the UHF sleeve-dipole assembly so that its five N-connectors are directly atop

the mating N-connectors on the main chassis topside. (Since the UHF sleeve-dipole

array assembly is heavy and awkward to handle, this and the following related steps are

Figure 6 - UHF Sleeve-Dipole

Array Installation Figure 7 - Turnbuckle

Fastener Detail

Figure 8 - Kevlar Guy

Tie-Down Detail

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best accomplished with two people.) See Figure 1. Exercise caution in this and the

following related steps so as not to damage the N-connector threads.

11. Rotate all 5 sleeve-dipole connectors counter-clockwise to verify that they are fully

loosenedanddisengagedfromthechassisconnectors. Alsoverifythatthesleeve-dipole

array is completely vertical with respect to the horizontal chassis surface.

12. Slightly finger-tighten any two opposing connectors until the threads just “catch” (once

the threads catch, do not tighten any further for the time being). Repeat this procedure

forthe othertwo opposing connectors. Once these threads catch, repeat this procedure

for the center connector.

13. Continue to progressively finger-tighten these connectors in the above sequence, being

sure to tighten each connector no more than 1/4 turn at a time (so as to prevent thread

binding) until all connectors are fully finger-tightened. If binding occurs, grasp the UHF

sleeve-dipole assembly near the top with one and gently pressure it back and forth

horizontallywhileattemptingtofinger-tightentheoffendingconnectorwiththeotherhand

(this will help relieve the binding).

14. To verify that all the connectors have been fully finger-tightened, again grasp the UHF

sleeve-dipole assembly near the top with one hand and gently pressure it back and forth

horizontally while attempting to continue to tighten the connectors with the other hand.

(Thiswillhelprelieveanythreadgallingorbindingthatmightpreventtheconnectorsfrom

fully finger-tightening.)

15. Whennofurtherfinger-tighteningispossible,carefullyinspecttheassemblytoverifythat

the sleeve-dipole stalks are perfectly vertical with respect to the chassis. If any tilt is

visible, loosen all five connectors slightly and repeat the above steps. Do not proceed

to the next step until no tilt is visible. It is imperative that the all five connectors be fully

seated and that there is no thread galling or binding. As a final check confirm that the

distances between the 5 sleeve-dipole connector lower rims and the chassis connector

flanges are all visibly the same.

16. With the connectors fully finger-tightened and the sleeve-dipole assembly confirmed to

have no tilt with respect to the chassis, continue progressively tightening the connectors

in succession using pliers. To prevent binding, tighten each connector only 1/8 turn at

a time. Repeat this successive tightening process as many times as required until all 5

connectorsaretight. Useonlymoderateforce. Also, donotinstalltheDAB-053Baerials

at this time. These will be installed during the installation phase. Premature installation

of these aerials will increase the likelihood of them being bent.

** WARNING **

Do not attempt to use pliers to tightenany connectors wherebinding ispresent.

Doing so will likely cause damage to the connector threads. If there is binding

that cannot be relieved by the procedures enumerated above, loosen all 5

connectors and repeat the procedure.

17. Note that the 4 Kevlar guy lines pre-attached to the sleeve-dipole array are terminated

with hooked stainless-steel turnbuckle fasteners. Insert these hooks into the

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corresponding guy bracket support holes on the main chassis sidewalls as illustrated in

Figures 6 and 7 (use the upper holes) and then tighten the turnbuckles. Be sure to

tighten these turnbuckles in pairs (opposing sides) by simultaneously tightening

the opposing fasteners so that the sleeve-dipole array is not pulled to either side.

(Rotate the turnbuckle fasteners clockwise to tighten.) To avoid damage to

internal components, exercise caution not to allow the chassis topside to bend or

bow while tightening these turnbuckles. Tighten to the point where moderate

finger pressure on the center of the line results in approximately 1 cm of play.

18. Apply a small amount of the supplied sealant compound (701-012) to the turnbuckle

threads (8 places as per Figure 7 to prevent the turnbuckles from loosening over time.

19. Inspect all installed hardware to verify that it is fully tightened-down. If any hardware is

loose, tighten-down with a wrench or pliers as appropriate using moderate force.

20. Inspect the junction between the mast flange and the main chassis underside to verify

that there is no space in between (i.e., the flange top should be fully flush with the

chassis underside). If the surfaces are not flush, remove the four bolts, verify there is no

debris on the mating surfaces, and reinstall (being careful to ensure there is no cross-

threading).

21. If it becomes necessary to remove the UHF sleeve-dipole array, loosen the connectors

in a successive and progressive manner similar to the procedure above by which they

were tightened.

22. This completes preliminary assembly of the DFA-1325B2. Do not attach the DAB-053B

and DAD-154B aerials to the aerial connectors at this time in order to reduce the risk of

bending during handling. These aerials will be installed during final installation as

discussed in the following Section.

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NOTES

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SECTION V - INSTALLATION

A. GENERAL

Once the DFA-1325B2 has been assembled as per Section IV, the remaining steps are to

select a DF site, fabricate a suitable mast mount, install the DAB-053B/DAD-154B aerials,

secure the unit to the mount, and then properly orient the DF antenna. These steps are

discussed in the paragraphs that follow.

*** DANGER ***

Installingoutdoorantennascanbedangerous. Anunsafeinstallationcanresult

in property damage, injury, or even death. With this in mind, the DFA-1325B2

installation should be done only by qualified personnel experienced in this field.

Since most users are not likely to have these qualifications and experience, we

strongly recommend that users have the installation done professionally by a

reputable contractor proficient in this line of work with a full knowledge of all

applicable rules, regulations, ordinances, and codes governing such

installations.

B. SELECTING A DF SITE

The importance of a good DF site cannot be overstated. Although the DFA-1325B2 yields an

instrumentaccuracyasperitsspecifications,systemaccuracycanbemanytimesworsethan

this if the DF antenna is installed at a poor site. Unlike mobile DF systems where poor

bearing accuracy can often be forgiven due to the tracking and homing nature of typical

mobile DF missions, mast-mounted fixed-site DF systems generally require a much higher

degree of bearing accuracy. This is especially true where the fixed-site DF system is a

component of a larger DF network used for triangulation.

The fundamental requirement for good DF antenna siting is that the DF antenna be mounted

so that it is free of obstructions. (Obstructions tend to cause re-radiation that leads to multi-

path reception at the DF antenna that in turn results in bearing errors.)

Although it is not strictly necessary that the DF antenna be mounted high off the ground, a

high installation is more likely to raise the antenna above the various obstructions that are

likely to be encountered (e.g., trees, buildings, utility poles, water towers, and even the DF

operatingconsole). A highinstallation is also advantageous inthat bearing errorsinduced by

non-uniform ground conductivity are likely to be reduced.

It is therefore important that a best effort be made to select a DF site that is as “clean” as

possible. Although site calibration is often a useful procedure for improving the instrument

accuracyofaDFsystem,itcannotcompensateforbearingerrorscausedbypoorsiting. (For

a fuller discussion of this topic, see paragraph V-F below).

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C. MOUNTING THE MAST SUPPORT PIPE

The bottom of the DFA-1325B2 isolation mast is designed so that it can be directly inserted

onto the supplied 2' long 3" inside-diameter schedule 40 stainless-steel mast support pipe

(S092-0002). Thismastsupportpipeinturnmust be safely mounted toauser-suppliedtower

or other suitable support structure. Since the details of the mounting technique can vary

widely depending upon user preferences and requirements, it is the user’s responsibility to

employ whatever construction techniques are necessary to safely secure the mast support

pipe to the support structure. In this regard, it is also necessary that the user obtain or

fabricate any custom fittings or adaptors that may be required to successfully complete the

installation.

*** DANGER ***

The support structure must be sufficiently strong to support the DFA-1325B2

under all conditions. If the user is inexperienced in large antenna mounting or

if there is any doubt regarding the ability of the support structure to support its

ownweightplusthatoftheDFA-1325B2underconditionsofmaximumwindand

ice loading, professional help should be obtained to guarantee a safe

installation. It is solely the user’s responsibility to ensure a safe installation.

There are a number of different mounting techniques available to the user. A common

method is to weld or bolt the mast support pipe to a steel tower. Regardless of the method

chosen to secure the mast support, it should be installed very carefully to ensure that it is

nearly perfectly vertical with no measurable tilt.

** WARNING **

Do not attempt to directly side-mount the DFA-1325B2 isolation mast against

a pipe, tower, chimney, or any other structure. Doing so will defeat its purpose

and prevent the DFA-1325B2 from being isolated from its supporting structure,

resulting in diminished performance. Also, the fiberglass isolation mast is not

designedforthestressesinherentinsuchamountingschemeandmaybecome

damaged as a result. (This mounting scheme is unsafe as well.) Always

construct a suitable mast mount as discussed above.

Regardless of the mounting technique selected, be sure to leave a sufficient length of the

upper portion of the mast support pipe unobstructed so that the DFA-1325B2 mast mounting

base can be slid onto the pipe and fully seated.

D. INSTALLING THE DFA-1325B2 ON THE MAST SUPPORT PIPE

Once the mast support pipe has been successfully installed, the DFA-1325B2 must be fitted

with its DAB-053B/DAD-154B aerials, mounted, oriented, and secured. To accomplish this,

proceed as follows:

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1. LocatetheDAB-054B(S024-0053)andDAD-154B(S022-0154)aerialsandinspecttheir

TNC male connectors to verify that they are clean and free of dirt and debris.

2. Similarly,inspectthecorrespondingTNCfemalematingconnectorstoverifythattheyare

likewise clean and free of dirt and debris.

3. Install the five DAB-053B UHF aerials on the mating TNC connectors atop the UHF

sleeve-dipoles. Firmly hand-tighten only - do not use a wrench.

** WARNING **

Once the aerials have been installed, handle the DFA-1325B2 very carefully so

as not to bend the aerial rods. Do not mishandle the assembled antenna, and

especially do not lay it down in such a fashion that force is applied to the rods.

4. CarefullyinspecttheDAB-053Btop-aerialstoensurethattheyareallinproperalignment

with respect to each other. This is most conveniently done by sighting the aerials along

each horizontal axis in succession and verifying that the 3 visible aerial safety tips line

up straight. If they are misaligned, bend the aerials slightly as required (grasping them

by the tips). Since there will likely be interaction between the two axes, repeat this

process as many times as necessary until both axes are properly aligned and all five

aerials are straight. Do not install the eight DAD-154B VHF aerials at this time.

5. Insert the free end of the interface cable into the top hole of the mast support pipe.

6. Retrieve this cable end by bringing it out through the lower end of the mast support pipe,

pulling it all the way through.

7. PositiontheDFA-1325B2mastmountingbase(atthelowerendofthemast)directlyover

the mast support pipe and carefully lower the DFA-1325B2 onto it. To prevent

inadvertent pinching of (and possible damage to) the cable, have an assistant pull the

cable from below so as to always maintain sufficient cable tension to prevent it from

bending while the DFA-1325B2 is being lowered onto the pipe. If resistance is

encountered, do not use force - lift the DFA-1325B2 off the mast support pipe and

determine the source of the blockage before proceeding.

8. Install the eight DAD-154B VHF aerials on the mating TNC connectors on the UHF

sleeve-dipoles. Firmly hand-tighten only - do not use a wrench.

9. Carefully inspect the VHF aerials to assure that they are straight, vertical, and in proper

alignment with respect to each other. Correct any misalignment by bending the aerials

as required.

10. Rotate the DFA-1325B2 as required to establish the desired azimuthal orientation (the

arrow or other marking on the chassis underside indicates the zero degree reference).

Oncethecorrectorientationisachieved,installandhand-tightenthethree1.0"longanti-

rotation bolts (605-009) at the base of the isolation mast. Once done, recheck the

orientation and then firmly tighten the bolts with a wrench using moderate force. Again

recheck the orientation to confirm that it is still correct. If the DFA-1325B2 is

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inadvertently rotationally misaligned during tightening, loosen the bolts and repeat this

stepasrequired. SeeSectionV-Ebelowforadditionalinformationregardingorientation.

11. Secure the DFA-1325B2 with four non-conductive guy lines. Attach these guys to the

support brackets located on the main chassis sidewalls (use the lower holes). We

recommend that these guy lines be made of a stretch resistant material such as UV-

protected Kevlar. When installing these guy lines, be sure that the tension on each line

is the same and that they not cause the iso-mast to bend.

12. If the DFA-1325B2 is to be permanently installed, we recommend that all mast mount

openings(includingtheexitopeningfortheinterfacecable)besealedwithanappropriate

weather-resistant compound. To facilitate de-installation, however, we recommend that

this compound be of a soft-cure removable variety (e.g., silicone sealant) rather than a

hard-cure permanent type (e.g., epoxy).

13. To prevent electrostatic discharge (ESD) damage, do not connect the DFA-1325B2 to

the DF receiver/processor before studying and complying with the necessary system

grounding and procedural precautions discussed in Section V-I.

E. ORIENTATION ISSUES

A DF system provides bearings that are relativeto the orientation of the DF antenna. In order

for these bearings to be meaningful, it is necessary that the DF antenna be oriented in such

a fashion that these relative bearings correspond to absolute bearings of a selected format.

A car-top mounted mobile DF antenna, for example, is usually oriented so that a zero degree

bearing corresponds to the forward direction of the vehicle. Similarly, a mast-mounted

shipboard DF antenna is usually oriented so that a zero degree bearing corresponds to the

forward direction of the vessel. In contrast, a fixed-site mast-mounted DF antenna is usually

oriented so as to be compatible with a geographical coordinate system. In typical fixed-site

installations, the DF antenna is oriented so that a zero degree bearing corresponds to true,

magnetic, or grid north.

Forthe DFA-1325B2a zero degree bearing occurswhen its “north-south”aerial axisis in-line

withthe signal source, with the“north” aerial closest to the signal source. The “north”, or zero

degree reference aerial is indicated by an arrow or other marking on the chassis underside.

We strongly recommend that the desired orientation be established based on appropriate

mechanical rotational alignment of the DFA-1325B2. That is, if a zero degree bearing is to

indicate true north, for example, the antenna should be rotated so that the two diagonally-

opposed aerials on the 0-180 degree (or “north-south”) axis are physically aligned with the

true north-south axis based on careful visual siting.

This is preferable to attempting to establish orientation based on the actual bearing received

byatesttransmitterorothersignalsourceofknownlocation. Thislattertechnique introduces

potentialerrorsasaconsequenceofpossiblemulti-pathreceptionandisthereforeunreliable.

16 of 29 - RDF Products - Vancouver Washington USA

RDF Products DFA-1325B2 User manual

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