RAOC-TR-72-151 Final Technical Report March 1972

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By ROIM Air 0*v«lep«i«nt C«it«r Air Fere* Syftwit Cemmond

Griffit« Air Fere« BOM, N*W York 13440

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RF BEACON GROUND STATIONS DISPERSIVE-PNASE/DIFFERENTIAL OOPPLER

MEASUREMENT SYSTEM

Electrac, Inc. Anaheim, California

Sponaorcd by OafMW« Advanced Rasaarch Projacta Agancy

ARPA Order No. 1057, Aaand. 15

Approved for public raleaae; dlatrlbution unlimited

P 0 c 1

C u

The viawa and eonduaiona contained in thia docuaant are thoae of the authora and ahould not be interpreted aa neceaaarily rapraaanting the official polidea, either expreaaed or inpliad, of the Dafenae Advanced leaaareh Projecta Agancy or the U. S. Cove t.

NATIONAL TECHNICAL INFORMATION SERVICE

U 5 D-.poflmnnl of ConmGrce Springt: ,IH /A ?7MI

DISCLAIMER NOTICE

THIS DOCUMENT IS THE BEST

QUALITY AVAILABLE.

COPY FURNISHED CONTAINED

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Electrac, inc. 1614 Orangethorpe Way Anaheim/ ealifotrnia 92801

3. HEPORf DTLB ""'

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Unclassified SI». GMOU*-

RF Beacon Ground Stations Dispersivo-Phaso/Differential Doppler Measurement Syr.Lern i*«*'*'*«.*

*. DL.5C.,in,vi- NOTES m-po o/ fepwt end (ncfu,/ve dnteV/" Final Technical Report

». AU rHOKisi fF<f»f n«/««, mVde«. Mllaini»! nam'eT

Raymond W. Honey

e. HFCOI-, T DA Ti:

March 1972 ••. CONTRACT OR O^AK KO

F30602--71-C-C022 b.

ARPA Order No. 1057, Amend. 15

I t0. OISTRIBUTIOKI STATI.I.nTlf"

/•l. TOI Al. NO. Of- PAG1.S

23 ■'!•. NO. DC Kl I b

0 JH. OM(i\Ui.TOH,S IU.PORT NUMBSRt«)

E.I. 77 3 8

...

RADC-TR-72-151

Approved for public reJoaso; distribution unlimited. 11 lUPfLtiMFNTARV NOTES ' ""

Monitored by: Richard Carman, RADC, (OCSi;), GAFB, N.Y. , 13440

I ^ Al ;. 1 K A c

tl.t T AN y A C t I VI T

Advanced Research ProjccL.s Agcnc Washington, D.c. 20301

In support of the SECEDE II barium release RF Beacon Test Serie«. Electrac, inc., designed, fabricated, installed and operated on site ^r?«^^1^11"'^1"0"^141 Do^lvi- Measurement Systems. The' experiment » primary purpose was to further the diagnostic oblective of obtaining descriptive information abOU the barium ions produced in the test series. The cloud parameter to be measured was the integrated ! electron density along a line-Of-sight as a function ot the line's ^iftilSl!: Lilien, Of prime interest were integrated density

TniSrr;?,*t d^cribos lhc measurement system, including dosion criteria ?S2J 2?\SnJi^rati;n 0f UK: £OUr •,yStC,1'iS as in^aUecl in the field rhree of the four systems were configured to receive the four rocket- borne beacon emissions at 145.7, 291.5, 437.3 and 874 MH*. The fourth system installed with the U.S. Army Bellistic ^search Lab syUm was configured to also receive at 36 MHS. A tape recorder was utilised Sd record both real time data (solitude and phase) 2S r^J S.U. ^iS LOOk system status was provided by simultaneous recoiding of the ampli- tude and phase data on strip ohari recorders. Additional provision were included for control, display and field calibration of each sy^trr,.

Typici.l data is presented bo show real time system performance under Cloud OCCttltation conditions. All systems wore opera I inn.. I and „rol vided the neu Uiits data during each oi th.e s.Mu.d .] ,i .v nt s P i

f> - M.. ,1473 4A. üncla§Rif^ed.

UnclasK.rf i cd Si curil ,• ClaHBification

».it >•.>■ i<(ii

RADIO BEACON RECEIVER

DISPERSIVE PHASE MEASUREMENT

DIFFERENTIAL DOPPLER MEASUREMENT

ELECTRON DENSITY MEASUREMENT

DOPPLER TRACKING

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Mil". A

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RF BEACON GROUND STATIONS OISPERSIVE-PHASE/DIFFERENTIAL DOPPLER

MEASUREMENT SYSTEM

Raymond U. Honey

Contractor: Elcctrac, Inc. Contract Number: F3O602-71-C-Ü022 Effective Date of Contract: 19 August 1970 Contract Uxpiratlon Date: 15 January 1972 Amount of Contract: $367,885.00 Program Code No. 0E20

Program Mnnaver: Project Engineer:

Piione:

Project Engineer: Phone:

Contract Engineer: Phone:

Irwin J. Weber Raymond W, Honey 71« 879-6021

Vincent J. Coyne 315 330-3107

Richard Carmen 315 330-2478

Approved for public release: distribution unlimited.

This research was «unnortcd by the Defense Advunced Kerearch Projicts Apenry of the Denarir.ent of Pefense and was monitored by hich.rd (amrn KADC (OCSE), CATS, NY 13U0 uncer contract F3^ Ctt-Vl-C-ara, /unend- mcr.t Ko. 15*

^M

PUBLICATION REVIEW

This technical report has been reviewed and is approved.

iJ^

UcJuUpj^/Gt^ ut*S RADC Proje^ngineer/ RADC Contract Engineer

ABSTRACT

In support of the RECEDE II- barium release RF Boacon test series,

Elcctrnc, Inc. designed« fabricated and fielded four Disporsive-

Phase/Differcntial Dopplor Measurement Systems« The experiment's

primary purpose was to further the diagnostic objective of obtain-

ing deseriptive information about the barium ions produced in the

test series. The cloud parameter to be measurcid wa« the integrated

electron density along a line of sight as a function of the lines

cloud-penetration position. Of prime intoroct were integrated

density atriations.

This report describn«; the measurement system including design cri-

teria aid final co.'ifiquratJ on of the Conr systems as installed in

the field. Thrcr of the four systems were configured to receive

the four rocket borne-beacen emissions at 14 5.7, 201.5, 4 37.3 and

B74 Mil:-. The fourth system installed with the U. S. Amy Ba.llir.ic

Research I.ab system was configured to also receive at 3f. Mil:'.. A

tap'.- recorder wa«; utili: ed lo record both real time data (amplitude

and phase) and row data. "Oxiick-IooV system sLatus was provided

by simult^nooun recording of the Mplitttdo ami phase data on strip

chart recorders. Additional provision!; wore included for control,

display ar.d field calibration of each system.

Typical data ia presenled to chow roa' tine synlen performance

under cloud occultniion conditions. All ■yotOM were operational

and proviHtd Liu» ngulbltc data dining each ol the scheduled event i .

77in iii

TABLE OF CONTENTS

1.

2.

3.

4.

5.

6.

Abstract

INTRODUCTION

INSTRUMENTATION

SYSTEM ASSEMBLY CALIBRATION AND CHECKOUT

FIELD INSTALLATION AMD OPERATION

SECEDE II OPERATIONS

CONCLUSION AND RBCOMMBNDATIOHS

Appendix A — Antenna Patterns

PAGE

iii

1-1

2-1

3-1

4-1

5-1

6-1

Figure 2-1

Figure 2-la

Figure 2-2

Figure 2-3

Figure 2-4

Figure 2-5

Figure 5-1

Figure» 5-2

friciflilMU

ILLUSTRATIONS

Di sperr ivu-Pli.-Uf/r'ifforontial Dapplev Moasurejucnt System

Bleak Diayram, Sacooc II Koccivor System

Rocommondod Geomolry and Resulting Values of Dispornion

Values of Interest in Secede CccmeLry

Map of Tost Area

Strip Chart Data

Beacon (Dinpersivi:"Phnce) Hocordc fran Site 3, Olive Early-Time Beacon

Beicon (Difspercivr-Phafio) Pccords from Si tc 1, Kvent Spruce

IM

2-2

2-2a

2-3

2-4

2-5

2-6

5-2

5-1

77 in

1 — INTRODUCTION

1.1 BACKGROUND

Extensive measurements of high altitude barium roleases

in the presence of sunlight have given considerable information on

the Ehdpes of the neutral and ionized barium clouds as well as their

motion in the atmosphere. In early times, both the neutral and

ionized clouds have simple .-.hapes and can be explained in terms of

diffusion a\my from the initial core. Sunlight ionizes the neutral

barium in a multistep process. Calculation of the rate of ioniza-

tion of the barium has proved difficult because large barium clouds

arc optically thick (in the important absorbing lines) to the solar

radiation. Thus one cannot calculale the ionization distribution

oven for the simple shape during the quiescent early times.

The SECEDE II release scries was conducted in the northern

Gulf Coast of Florida in January of 1971. Six barium releases were

made, at heights ranging from 150 through 2i>0 ];m. Barium mix lay-

loads arc 4H kg on five releases and 352 kg on one release. A rocket-

beacon war used to transmit through the barium ion plasma to ground

sites.

The beacons were aimed to pass behind the barium clouds

and nearly transverse to the gcomaqneLic field lines as soon from

the receiviiig Rites.

7718 1-1

The well known dispersivo-phase technique takes advantage

of the dispersive nature of UI1F-VHI' propogation in an ionized medium

to measure the phase-path deflect, or shortening of the phase-path

length between a transmitter and receiver. Under several assumptions,

the phase-path deflect is accurately proportional to the integrated

electron density or electron content, N., along the path.

1.2 OBJECTIVE

During the series experiments wore conducted to measure

integrated electron density along a line of sight as a function of

the linear cloud-penetration position, including integrated-density

variation in space due to Lhe presence of plasma density striations.

This line integral, sometimes referred to as "total electron content",

was measured by moans of ground observations of signals transmitted

from a radio beacon carrier behind the ion cloud on a sounding rocket.

The technique for measuring total electron content in-

volved observing the differential-Dopplcr shift (dispersive phase)

on two coherent CW signals that pass through the plasma. The choice

of frequencies depended upon the content anticipated. To cover a

wide range of electron densities, the Doppler shift of 146, 292 and

437 MHz was measured with respect to 87 5 MHz, Phase-path differences

and amplitude were measured. Four ground receiving stations were

included to increase the probability that the beacon rocket would

pass behind the barium cloud as viewed from at least one ground site.

7718 1-2

The di f iVriMil.iol pliaso meacuromont in roforrcd to the

lower of tho two f xeqmncic:;. Thus, if the rroquoncics are f

and nf, and tho phaM di^rcvonco, ^L, is consput^d (offactively)

at f, tlM error tolerances are spocilicd on tho rocovorod phase

shift nl f, 0^, whore

^f ' T8-? ^d n - \

Tho 074.59 MHz sional is tho upper frequency for all the ir.easure-

went pa:rs. Amplitude moasuremontn are made at all frequencies.

7718 1-3

2 — INf.TRUMKWrA'nON

2.1 Tbf EU-rtrac PliptniT» tfUM9 Dif f crcnl i il DoppKr Measure-

mont Systoin i :•. usi-d for the Moasurcmc-nt of signal amplitudon and clif-

forontial phase of four or five cohorc-nt froqvjcncios in \hr range of

36 to 874 MH... The- r.v: tew is configured as chown in Figvii.v- 2-1 and

2-la and conrir-ts of the .-quip.er I s Listed in paruqraph 2.2. The

eyster,. intri.accs with pagnotic tape waA/ot r.trin chart rc-i-orders for

display or recording o.r both ronl-timc ant raw oulput data.

In a tvpical installation scenario (r.ec figures 2-2, 2-3,

and 2-4), (ach system in placed approxirately 20 In apart parallel to

a rocket trajectory. Syytom design criteria ineludofl lino-of-sight

distance to the launch site eC at least ISO In and rocket apogees of

2,;»0 to 400 In. Ion cloudj (typically a Harium mi::) are placed sepa-

rately at I8S km on tlie down Log of the !. rajectory. The rocket pnth

profile is specified as falling P.5 km behind the cloud. The rocket

borne coherent frequency trans: itlors are tracked fm launch to im-

pact. Typical strip chait dala is illu~l rated in ri.jure 2-f). For

this presentation, th-.; chart has. been cvt into three segments.

Differential phase measurements are made continuoasly

with the system by conparir.cf the lender received frequencies with

the received higher,t frequency as a reference. To resolve dif-

ferential phase advance or retardation in ■ dispersive environment.

77in 2-1

DXSPERSlVE-PHASE/DirrEBEHTIAL

DOPPLE* MEASUREMENT SYSTEM

Figure 2-1 2-2

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Ill

I-MODEL ♦IOZA (SBO 4I02B (BRL)

ANTENNA MAST EQUIPMENT

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(ima •)

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Figure 2-la

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both Lhc sin« and cos of differential channels ure available.

Simultaneously, amplitude measurements are made« on each of the

transmitted carriers. As shown in Firjure 2-5, the upper four

tracks represent the amplitudes of the received signals at approx-

imately L45»7| 20.1.5, 437.3 and «74.6 Mil?.. The lower four tracks

are indicative of the followinq differential phase measurements!

a) 145.7/874.6 sin

b) 145.7/871.6 cos

c) 291.5/874.6 sin

d) 437.3/874.6 sin

A notable achievement of this measurer.ent system is its

capability to track a spfnnir.e tarqet. This is shown as a 3 rps

rate of the boostcr/pavlead riior to tä^rtaqimi «md a subsequent

ppe.'d up to B rps after desLaying. The phase data is "self cali-

brating" in thnt the difference is presented as a trianqular pat-

tern with a peak-to-peak excursion correrpondinq to -90 and +90

degree phase c'.nnge.

Quite evident i»i i'uiuro 2-5 are the ionosphere differ-

ential pha-e counl up and tlu- resultant speedup due to oecultation

with highly dense ion cloud!, as well as the ditfractivc effects on

7710 2-7

the amplitude oC the lower frequency niynals. This data can thus

be utilized to detennine the "total electron content" of the ion

cloud.

2.2 EQUIPMENT CONFIGURATION

The Electrac developed system for one (1) ground station

is shown in Figure 2-1, and consists of the following:

Antenna Mounted Units

Electrac Model 4108B, Crossed Loy-Periodic Antenna

Electrac Modo] 4102A, 4 Channel RF Preamplifier and Multicoupler

Electrac Model 4102D, 5 Channel RF Preamplifier and Multicoupler

Rack Mounl-.od Units

Electrac Model 606A-1, 36 MHz/2 kHz Down Converter

Electrac Model G06A-2, 145 MHz/8 kHz Down Converter

Electrac Model. 6ÜGA-3, 291 Mllz/16 kHz Dowi Converter

Electrac Model G06A-4, 437 MHz/24 kHz Dovm Converter

Electrac Model G06A-5, B74 MIIz/48 kHz Down Converter

Electrac Model 605A, Frequency Synthesizer

Electrac Model G07A, VCO Multiplexer

Electrac Model 3713D, Pour Channel Tracking Filter or Model 375D-215, Five Channel Tracking Filter

7718 2-8

Tho tquipuicnt. WM r.uppli*^ to tho U. S. Air Torcti,

Rome Mr Dovclop.nont Conlcr in tlu« four-chanucl confiqurai.ion

and to Lho U. 51. Army taHlistia l^u-arch Lal>oral.oric:r. in the

fivc-chnnnol configuration.

The four-chamuH conficuuationR included a Bell and

Howell Macjnotic Tapn Rccordcr/Kep! (.cu.ccr. Hodc-l VK3360 as shown

in Figure 2-1. Al^o shov;n is a typical inslullation with a strip

chart recorder.

A set OH typical antenna patterns is inolttdod as App-ndix

A. Data includes cuts takM l» 1'oth orthoqcnal planer, as well as

circulari ty measurements.

7718 2"9

3 — SYSTEM ASSKMHLY CALIBRATION AND CIIICCKOUT

After the Electrac instruinontation pystem had been

initially mochani/.ed, it was found that the required system AGC

recovery time necessitated redistribution of the non-cohorent nnJ

coherent AGC control. It was also necessary to add band pass

filters between the first and second mixers to correct very high

order harmonic c-ross-talk. The harmonic relation between the

various channels made it necensary to modify the tracking filter

to minimize false lock-up on adjacent channel harmonics. Finally,

it becano necessary to change from "greatest of" AGC to independent

channel AGC, in order to eliminate channel to channel cross-talk

in amplitude moiisurcmonts.

As originally plannedi all channels were to operate at

the same gain in the 2 m* "identical" IF amplifier«. With matched

amplitude and plnse characteristics, the differential effect would

have been minimised. The largest signal channel controlled the

gains of all channels. This non-coherent AGC signal was added to

the individual coherent AGC voltage. If all channels, both coherent

and non-coherent, were sufficiently matched in slope, an increase

in the st-ongest. channel resulted in all other channels being

suppressed and their coherent AGC changing to cancel the change

in non-coherent AGC. In actual operation, it was not possible to

maintain sufficient slope matching and an increase in one channel

coupled in varying degrees to all channel AGC outputs.

iV „„itch VM« added to allow each channel to be operated

independently, eliminating the cross coupling. This, however.

resulted in r,o„,e sacritice in phase accuracy since each non-coherent

AGC operated at its own level depending on its signal strength and

the common modo canoe] Icttion was lost.

These changes were carried oul. concurrently with equipment

fabrication and assembly because of schedule pressure.

m its final configuration, the phase-lock tracking filter

drove phase detector that provided triangular-wave outputs of dis-

persive phase between each of the measurement frequencies and the

reference. Since there is a 180° ambiguity in the output of this

type of phase detector, a second detector at each measured frequency

provided an output shifted by 90° to resolve this ambiguity. These

outputs represented the prime data, and were recorded on magnetic

tape. in addition, the amplitude of the received signals was also

recorded, as well as timing signals and "raw" received signals. The

latter were low-frequency IF signals that drove the tracking filter

and this could be directly recorded.

Variations of the phase and amplitude outputs were also

put on strip chart records to act primarily as quick look data for

field evaluation of operations and results.

3-2 7718

Prior to beacon launch, and after the last beacon splash

down, calibration signals were recorded, prtaarily to establish the

AGC calibration. A stability recording preceded and followed the

beacon flights, the stability test signals si-.ply consisted of a

steady input to the receivers. Acquisition of the beacon signals

typically occurred within three to five seconds after launch.

7718 3-3

■

4 ~ FIELD INSTALLATION AND OPERATION

Throo syetoms were built in the four-channel configura-

tion and one system in the five-channel version. The following

equipment deliveries were made»

One Antenna to Ballistic Research Labs 30 Nov. 70

Three Antennas to Tyndall APB 14 Dec. 70

One Experimental Model, four-channel 14 Dec 70 version, to Tyndall Am

One Experimental Model, five-channel 24 Dec 70 version, to Tyndnll AFß

One Experimental Model, four-channel 31 Dec 70 version, to Tyndall AFB

One Experimental Model, four-channel 02 Jan 71 version, to Tyndall APB

In addition to the above items, operating spares were

shipped to Tyndnll APB on 08 January 1971; and to Stanford Research

Institute (SRI) on 19 February 1971 and 08 March 1971. Data chart

records for the Nutmeg, Plum and Redwood events were shipped to SRI

on 16 March 1971. Chart records from other events wore delivered

to SRI infonrally at the test site. Original data tapes were hand

carried to SRI by Dr. A. Burns.

The Acceptance Tost Procedure was delivered informally

to the test site with the equipment, together with test data taken

at the Kloctrac plant. The procedure was incorporated in preliminary

operating instructions prepared for Electrac field personnel.

7710 4«!

Electrac field personnel left Anaheim for Tyndall APB

12 December 1970 and arriv.cd at the test site 17 December 1970.

The installation and test work was completed 6 January 1971. First

flights were begun 7 January 1971 with a helicopter beacon checkout

flight. The operation and maintenance phase of the work continued

from that date until 2 February 1971. Three days were required to

clean up the various sites and pack the equipment for shipment.

Electrac personnel departed the test area 5 February 1971 and arrived

at Anaheim 10 February 1971.

7718 4-2

5 — SECEDE II OPERATIONS

The Electrac Dispersive-Phase Differential Doppler Measure-

ment Systems were all operational during the beacon experiment. Data

were collected on all of the Secede II releases except REDWOOD, where

both beacons failed to pass behind the cloud with respect to the re-

ceiving stations. During the NUTWOOD event, failures (due to beacon

antenna breakdown) of both the main reference frequency (874 MHz) a.d

the alternate reference (437 MHz) prevented obtaining dispersive

phase data, although there is some hope of making a phase comparison

between 145 MHz and 291 MHz with the "raw" recorded signals. On the

other releases, at least two of the dispers.;.vc-phase sites received

cloud-affected signals from at least one beacon. Considerable high

quality data, corresponding to spatially separated slices through

the clouds, were thus obtained, particularly for the arly-time

smooth (non-ctriated) clouds. The Spruce data are for the period

just after striations developed and represent all the striation data

obtained.

Figure 5-1 shows the chart record from a typical early-time,

smooth-cloud occultation, in this case for Beacon 1 and S-3 on Event

OLIVE. The top four channels chow the signal amplitudesr the rest

are dispersive-phase records, including the 145-MHz quadrature phase

output. Each full cycle in the latter set of records roprcsonts

360° of dispersive-phase change, with the phase reference in each case

being the 874-MHz signal.

7718 5"1

5 ? »:.: »^ «ft

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5-2

The triangular, phase-detector output waveforms at the

right and left ends of the record resulted from the ionospheric

contribution to N . The obvious increase in rate of dispersive-

phase change through the middle portion of the record is the con-

tribution of the early-time (about 150 seconds after release) OLIVE

ion cloud. Near the center of the record, N. reaches its maximum,

where the slope of dispersive-phase change is zero. Note that

refraction caused N. to reach its maximum value at different times

on different frequencies.

A different sort of occultation record appears in Figure 5-2,

obtained at S-l about 14 minutes after the SPRUCE release. The top

four records are of the four signal amplitudes and the bottom two are

of the 14 -MIIV874-MHZ and 437-MHr:/874-MHf. dispersive phases.

Although missing the main body of the ion cloud, the

beacon line-of-sight crossed the portion of the cloud that had begun

to show striations. Thus, most of the regular (triangular) phase

changes seen are duo to the ionosphere.

The 437-MIIz records afford the best description of the

occultation. At the beginning there is an abrupt change in the

dispersive-phase slope, followed by a relatively rapid increase in

N. to a maximum four seconds later. Following this maximum, con-

siderable small-scale structure is visible, much of it below 100 m

in size, a rough estimate based on the time duration of the small

features and an estimat -d rocket velocity ot about 500 m/sec.

77in 5-3

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UP m.VvOd 1AMVI III

6~ CONCLUSION AND RECOMMENDATIONS

Electrac, Inc. designed, fabricated, and fielded

four Dispersive-Phase/Differential Doppler Measurement Systems.

Experiments were conducted to provide data on integrated

electron density and wavefront distortion. All systems were

operational and provided a considerable amount of high-quality

data.

The systems were designed to provide data on amplitude

as well as phase. Since both the amplitude and phase

readouts are directly affected by non-linearity and/or phase

shift in the AGC attenuators, it is felt that although the

attenuators were sufficient for these experiments, improvements

could be made. In particular, the non-cohbrent attenuators

are in need of additional design effort to make the system

more accurate at strong signal levels (greater than -95 dBm

Wherein the non-coherent AG- begins to operate).

Since the phase comparators in the model 375D

involve several dividers with no provision for presetting,

each time the system is turned on and locked, even for

repeated runs on the same tape data, the phase outputs start

at any one of several random fixed offsets. Although this

can be taken out in data reduction as a constant offset, it

might be more convenient to consider providing reset signals

7710 6-1

or a means of advancing or retarding the signal count BO that

particular phase points could be chosen at the start of a

record.

The system as used had poorer noise figures than antic-

ipated particularly in the 437 MHz channel and future systems should

consider means of reducing the noise figure and as a consequence

improve the system threshold.

ACKNOWLEDGEMENT

To the mary people who contributed so greatly and

with much extra effort in order to enable us to get into the

field operationally and on time, our sincerest thanks. Key

Electrac personnel involved in the various phases of the program

included the following:

System Design

L. Katz

I. Weber

R. Honey

Hardware Design Field Operations

R. Honey

L. Wells

J. App

I. Weber

J. Gobel

R. Terrell

Final Report

R, Honey

Consultant: Dr. A. J. Mallinckrodt

7718 6-2

APPllKDIX A

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