IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. EMC-25, NO. 3, AUGUST 1983 133

EMC Twenty-Five Years AgoLEONARD W. THOMAS, SR, LIFE FELLOW, IEEE

(ADAPTED FROM THE KEYNOTE ADDRESS FOR THE 1978 IEEE INTERNATIONAL SYMPOSIUM ONELECTROMAGNETIC COMPATIBILITY) 1

I. INTRODUCTION At a luncheon on February 27, 1957, during the Third

IN THIS TALK, I draw upon some interesting and perhaps ARF Conference on RFI, Fred Nichols was scheduled tolittle-known facts and incidents from the period both before deliver an after-luncheon speech about the Radio Interference

and during the era of 1958. I have organized my talk on three Technical Committee in the Los Angeles area, of which

general areas: 1) organizations, 2) specifications and standards, Committee Fred was Vice President. In the early morningand 3) measuring instruments. hours of February 27th, before Fred gave his speech, six

First, a few general remarks. Our chosen field of endeavor men-A. Zimbalatti, J. Lucyk, A. Ruzgis, S. Nellis, M. Kant,has been too frequently misunderstood and often ignored by and H- Schwenk-discussed the idea of forming an organiza-many people. As an example, I will cite one instance of tion for eople interested in RFI. They asked Fred to give a

misunderstanding. plug for such a group in the New York City area, which he

Stan Bennett, an EMI/EMC engineer with the Navy's did. This was followed up a few weeks later by a letter to a

Bureau of Yards and Docks, was directing a group of con- number of people in the New York City area, inviting them totractor engineers who were making field-strength measure- attend an organizational meeting. It was well attended, andments at a Navy installation on the West Coast. There were it was voted to start such an organization and to petition theseveral Naval officers observing the tests. One of them ap- IRE for the establishment of a professional group on RFI.proached Stan Bennett and asked him what those men were This group was approved by the IRE on October 10th, 1957.doing with all of those instruments. Stan replied that "they The first chairman of the group was Harold Schwenk.were making field-strength measurements," to which the Navy During the first meeting on November 20th, 1957, in Asburycaptain, after stamping his feet on the ground several times, Park, NJ, an administrative committee was formed and futurereplied "this field appears strong enough to me." activities were planned, including holding an RFI symposium,

While we are not as much misunderstood at the present sponsoring RFI sessions at the annual IRE conventions, startingtime as we were many years ago, there still exists the need in March, 1958, and the publication of RFI TRANSACTIONS.for education and enlightenment of the general public- The first officers of the PGRFI were: Harold Schwenk, Chair-and some engineers who should know better-on just what man; Leonard Milton, Vice Chairman; Albert R. Kall, Secre-EMC is and what our goals are. tary; and James McNaul, Treasurer.

Members of the first PGRFI adminstrative committeeII. ORGANIZATIONS were the following:

Where was our EMC organization twenty-five years ago One-Year Term Two-Year Term Three-Year Termwhen it was known as the Professional Group on Radio Fre-quency Interference (PGRFI), one of the several Professional R. Fairweather S. Burruano W. CrichlowGroups of the Institute of Radio Engineers (IRE)? L. Milton J. McNaul Z. Grobowski

Initial efforts toward organizing a group on radio-frequency B. Schenker A. Kall M. Kantinterference (RFI) took place in 1956 during the Second H. Schwenk W. Pakala R. ShowersARF2 Conference on RFI in Chicago, IL. There was a sug-

, 'T~~~r* The PG-RFI sponsored an RFI session and participated in agestion made that people interested in RFI form an organiza- j rr r. ~.,~., . 11~.. n ~..joint session on interference to communications during thetion. This idea was printed in publication called "Quasies and M 2-2, , t i i iMarch 24-27, 1958, at the IRE National Convention in NewPeaks," the Editor of which was Rexford Daniels of the k C

Interference Testing and Research Laboratories in Boston, MA. r ty.On October 1 and 2, 1958, the PG-RFI cooperated with theInterested readers were requested to contact Milton Kant of and, ,Armour Research Foundation and the U.S. Army SignalSperry. Only three replies were received, and nothing hap-Sperry.Only three replies were receiv, ad notg Research and Development Laboratory in conducting thepened. Fourth Conference on RFI in Chicago, IL. Col. Harold Brown,Commanding Officer of the Laboratory at Fort Monmouth,

Manuscript received April 28, 1983. delivered the introductory address. Even though it was de-The author is at 1604 Buchanan St. NE, Washington, DC 20017. livered twenty-five years ago, it still carries the same message1 Guest editorial by L. W. Thomas, Sr., "EMC twenty years ago,"

IEEE Trans. Electromagn. Compat., vol. EMC-20, pp. 473-482, Nov. to us. May I read a portion of his address?1978.

2 Editor's Note: Armour Research Foundation, now IIT Research Unfortunately, there has been a tendency on the part ofInstitute. many of us in electronics to treat the problem of inter-

0018-9375/83/0800-0133$01.00 © 1983 IEEE

134 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. EMC-25, NO. 3, AUGUST 1983

RF Interference WorkTermed Urgent Need

NEW YORK.-R di Itl advnes in radio frequency In-terference control, _ well u bet.er in.tmen-tend.tandardfor interference measurement, ere decribed as urgent needaat aseminr hereer at week.

nreuing eff.ortyae being m Ade by the militry to on-centrateon elmintin Intter er-enee p oblems In ti ri y designsages of ne nhardware deapi thetact that not enoUgh bele In-

TheAIr Researeh A DIvelopmentCommndDOverp eine ern.ms nd

Irying to develop tTei for deLgn Y. 1tengin Ltiehiers. inn tb« n Vol FI-1, No. ot MAY 9M

eWeadt b th ornlre u. e Attor adio 24advanineIteaes o!ettiar,r semionsuotnedd wee kbt1H IIREPrtoional Group onlnds O hither-overa eeRdiiCrbeltitrnwith 1cYoot. StandingelemiitaLiE Ot CONTENTS

thb ~ ~ ~ ~ ~ ~Wileu tb yt t LijaelY' .RiM, SnaiRUnivioof eonoer A ennioee

CEquipmentmOtIrt ptsletalonl ihn Ct Rlc~NoteqL nomt -i of ThenoughnCheoi end CnrdChrmn dlertie LopePertSnhont adetheierere etewlo

Aett lateeriMton,whsch oonemgew, ao lM. .te Meo

de~a~n.I. I.,

Eo inquipmentr uiV.. II-,N.ei.leild MAe" M

Electronic Neiwvs dcmillaediSt m Wdt AtttooA mearomhntn toposerly

ErKveni ohtwe wn-,.N. hyjt Ftth1n1 tffMleipie-Ci edthu Cpito- i

WWhta iCndutn nest utt Ded Jungen a fQhoP oDfet ecr uingt Iindum nstnt Y.

o prmthentoo rv wrieemnebeyn amonsyIne lea enotst tariis op

toest.tblls Un bort od t" oL De p dou b. Biogrnphieofr ultslh.oweerWi ionf he rs t Itdlcd. adlel etaeuiennrle ginwlun

Gre .t NkM. T4, IIIn tpot ith fuquency

loathir n tdedwt he down roherowefequencyppraSA.

e t rsen ted ei ah r eaoloaAncMta a el n needdiffr gon

unidi ifItwm pn ed urs tt. IfUt the et it rm_unit

lan· inttote rletm t hit rulyl m rCl

eludled. M.r O i. .n.l help". Mr.

Eutelectron i cNewmetst nid. fRIm nly to. met to d i ..irDaarr tpeol

enl Cip anny Ircod dcete or It nsprodcumtdt

June 22, 1959 entinr ' d eet. betR.

Nnrdum p onofw_ theNWoea-. ehfrtFtonn..ChMter eret n. W ork i. MaK.Loa Thomas, end atH.tbFen_

Fig.i. News onte it heIRE RFI symposium

wsheFig. 2. Cover on the first IRE PGRFI Transactionster.ference either as a necessary evil or one which would goaway if we ignored it. We have poured huge human and authors aned contained 25 pages. The chairman of the publi-financial resources into the development of truly mar- cations committee was . P. Schreiber assisted by Williamvelous electronic equipments and systems, only t have Jarva and Rexford Daniels.them rendered, in many instances, completely ineffec- A newsletter committee was appointed consisting of: Rex-

~tu~dealbeause we have failed to apply what would have f ad.ford Damels as chaaeerman and assosted by MdltonKant,Anthonyetbeenaridiculously small portion of theoverall effot toedil

the problem of interference reduction. Today, the folly Zimbalattr,Al Kal, Leonard Thomas, and Harold Schwenk.igof this oversight is clearly evident. On September 15,e1958, thte IRE PGRFI had 192 members.

1959, at the Park Sheraton Hotel in New York City. An article Sectional Committee C63 of the American Standards

Gsreatopm SCenter. Da s.Yd i . . `P.tomrat hesp freqen y

n te June 22,1959 issue of Electronic News cies thehea- Association ( , now thew Amerian National Standrds

line "RF Interference Work Termed Urgent Need"(Fig. 1). A Institute, had completed new drafts of tewo proposed Ameri-

photoaccompanies th artic eshowing the participants in can tandard C peciicationo In enoiseie .

the symposium.Pictured were: C. B. Plummer, FCC, Wash- and field strength meters, 0.015-30 MHz, and C63.4-(1957)

ington,DC; RM. Showers, University of Pennsylvania, methods of measurement of radio influence voltage andradio

Philadelphia; D. C. Ports, Jansky and Bailey, Washington, influence fields(radionoise),0.015-25MHz.

DC;Andrew P. Massey, Bur.eau of Ships, Washington, DC; The U.S. National Committee of the International Electro-

200engineers attended this first PG-RFI symposium. sideration by, the CISPR at their next meeting on NovemberThefirstissue of the IRE PGRFI TRANSACTIONS (Fig. 2) 18-21, 1958, in The itHague, e Netherlands. At this same

bears the date Mancy taa five time, work continued in Committee C63 on developing a

away if we ignored it. We have poured huge human and authors and contained 25 pages. The chairman of the publi-financial r esourcesinto thedevelopmentof truly mar-cth.velous electronicequipmentsandsystems,only to havepop-

them earendteredtteS Shapent mAinews,letiee wa inefe ted consisting of: Rex-tualbecuseweavefaiedtoapplywhatwou e ford Daniels as chairman and assisted by Milton Kant, Anthony

b eena ridiculously small portion of the overall effort to

O nS eptember15, 1958, the IRE PGRFI had 192 members.

The first IRE RFI symposium was held on June 15 and 16, were they donined1958 p

1959,a tthePark Sheraton Hotel in New York City. An article Sectional Committee C63 of the American Standardsi n the June 22, 1959 issue of Electronic News carries the head- Association (ASA), now the American National Standards

line"RF Interen ceW orkTermed Urgent Need" (Fig. 1). A Institute, had complete d new drafts of two proposed Ameri-photoaccompaniesthis article s howing theparticiptnoldhv fr Dansdards:C63.2-(1957) specifications f orradio noisethesymposium. Pictured were: Ctio.ToaPlummey C,F Wash- and field strength meters, 0.015-30 MHz, and C63.4-(1957)ington,DC; R. M. Showers, University of Pennsylvania, methods of measurement of radio influence voltage and radio

Philadelphia; D.RC. Portsi was hed onJuey 1 andt16, Winfluencefields (radio noise), 0.015-25 MHz.DC; Andrew P. Massey, Bureau of Ships, Washington, DC; The U.S. National Committee of the International Electro-A. L. Fullerto2,195pisu of EletonIc,MA; H. R. Schwenk, technical C ommission, anotherAmericnsNation t ASA,NationalChairman, IRE PGRFI; J. J. Egli, U.S. Army Signal forwarded 400 copies of each of these documents to the

R es e archand Development Laboratories, Ft. Monmouth; International SpecialC ommittee on Radio InterferenceandS. J. Burman o ,FiltronCompany, New York, NY. Over (CISPR) Secretariat as U.S. contributions to, and for con-200 engineers attended this first PG-RFI symposium. sideration by, the CISPR at their next meeting on November

The first issue of the IRE PGRFI TRANSACTIONS (Fig. 2) 18-21, 1958, in The Hague, The Netherlands. At this samebears the date May 1959. It carried three papers by five time, work continued in Committee C63 on developing a

THOMAS: EMC TWENTY-FIVE YEARS AGO 135

draft of another document: C63.3-( ) specifications for JAN-I-225radio noise and field strength meters, 25-1000 MHz. 14 JUNE 1945

At their Hague meeting, the CISPR adopted new member-ship and procedures rules and organized working groups to JOINT ARMY-NAVY SPECIFICATIONcarry on the work of the CISPR. Also adopted were 16 re- INTERFERENCE MEASUREMENT, RADIO, METH-

6 recommendations, and 23 stuy q . Sx d -ODS OF, 150 KILOCYCLES TO 20 MEGACYCLES

ports, 6 recommendations, and 23 study questions. Six dele-(FOR COMPONENTS AND COMPLETE ASSEM-gates from the U.S. attended these meetings. The influence BLIES)of U.S. participation in the work of the CISPR can be readily Army Number Navy Numberseen from the examination of CISPR publications. 71-3233 16-1-14EMC effort in the military twenty years ago was far from This specifcation was approved by the War Department andthe Navy Department for use of procurement services of the Army

inactive. The series of annual Armour Research Foundationandth Navy.A. APPLICABLE SPECIFICATIONS

Conferences on RFI, which were initiated in 1954 by the A-1. The following specifications, of the issue in effect on date of~,~ -i1 7. AInvitation for bids, form a part of this specification:Signal Corps Engineering Laboratories, the Wright Air Devel-

ARMY-NAVY AERONAUTICAL SPECIFICATIONopment Center, and the Navy Bureau of Aeronautics, were

AN-W-14--Wiring Installation of Aircraft.continued, providing the means for exchange of information ARMY AIR FORCE TENTATIVE SPlCIFICATIONARMY AIR FORCE TENTATIVE SPECIFICATIONconcerning RFI. Efforts were underway in the military depart-32412apacitors Fixed (Paper or Mica Dielectrlc).ments to improve and expand the scope of specifications and a. CLASSES

B-i. Electrical equipment tested under this specification shall bestandards pertaining to interference. The development of th.whlcts sitedb the applicable equipment specification or

measuring instruments to cover both higher and lower fre- the contract or order.C. MATERIAL AND WORKMANSEIP,

quencies was also underway. C-1. Material and workmanship of the testing apparatus required intests under this specification shall be suitable for the purpose intended,

The Federal Communications Commission (FCC), which and in accordance with current appropriate Army, Navy and com-mercial testing practices.

is cognizant of the nongovernment use of the radio-frequency D. GENERAL REQUIREMENTSspectrum in the U.S. has, from its establishment, been aware D-I. This specification covers the methods used in measuring radiospectrum in the U.S. has, from its establishment, been aware sinterference produced by electrical equipment in the frequency band

of the harmfuleffects of RFI. In the late 1957 the FCC from 150 kilocycles to 20 megacycles. For the purpose of this specifica-of the harmful effects of RFI.In the late 1957, the FCCtion, radio interference is defined as undesired conducted or radiatedelectrical disturbances, within the range of frequencies covered byissued revisions of Part 15 (Incidental and Restricted Radia- the specification, which may interfere with the operationof electrical

tion Devices) and Part 18 (Industrial, Scientific, and Medical communication equipment or other electronic equipmentE- DETAIL REQUIREMENTS

Service) of the Rules and Regulations to measure and control -l. Noise meter.-E-la. Standard meter.-The Ferris noise meter type 32B, or equiv-interference more adequately. In 1958, the FCC modified alent, shall be the standard instrument used for making radio inter-

Part 19 (Citizens Radio Service) of the Rules and Regulations.6842-4 (no.142)

Fig. 3. First U.S. joint military standard on RFI measurement methods.

III. SPECIFICATIONS AND STANDARDSfor commercial and government nonmilitary procurement

No person attempting to cover the history of EMC, when a measurementsand measurements.referring to the development of specifications and standards,should overlook the first attempt within the military to IV. MEASURING INSTRUMENTSachieve a joint standard on the measurement of interference.Such an effort was started in the early 1940's and resulted The forerunner of all interference measuring instrumentsin agreement on, and the publication of, a joint Army-Navy is shown in Fig. 4. Here it is, with its cover on, ready to go.standard JAN-I-225, dated June 14, 1945. That was before How many of you can identify it? It is the Ferris Model 32B,the creation of the U.S. Air Force (Fig. 3). This standard frequency range 150-350 kHz and 550 kHz-20 MHz. Here isserved for many years before it became obsolete and was a front view with the cover off (Fig. 5(a)), and another viewreplaced by individual departmental specifications, some (Fig. 5(b)). The operating instructions and calibration curvesof which were as follows: were in the removable cover (Fig. 6). If you wanted more

accurate calibration based on a sinewave rather than on aMIL-S-10379A-July 6, 1951-Vehicles;MIL-S-10379A-July 6 1951-Vehicles;' "shot-noise diode," you could use the Ferris Model 32XA5MIL-I-6051 A-Aircraft Systems; MIL-I-1external calibrator (Fig. 7(a)) which plugged into the top ofMIL-I-11683B (Sig C)-January 3, 1956-EngineGenerators; the Ferris 32B noise meter (Fig. 7(b)).MIL-I-17623(Navy)-July 2, 1957-Electric Office Machines; For measurements above 20 MHz, the MeasurementsMIL-I-16910A (Ships)-November 1, 1957-Electronic andMIL--16910A(Ships)-November 1, 1957-Electronic and Corporation Model 58 UHF radio noise and field-strengthElectrical Equipment;MElectrical Eq (Sig. C)-December 17,1pment957-Watermeter (Fig. 8) could be used. Its frequency range was 15-

ment;?...... ,<^oT^ i r ir r. Association subcommittee on television interference.

MIL-S-11748 (Sig C)-November 4, 1958-Electrocandft

150 MHz ( atthat time, UHF), and it was designe d in accord-

M'L-- 1748 (g Ce 4,1i measuring instruments in the 1940's, and by 1958 many newElectrical Equipment. instruments had been developed fulfilling both governmentalSome of these specifications were used in whole or in part and civilian requirements. A partial listing of these instru-

136 IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY, VOL. EMC-25, NO. 3, AUGUST 1983

_!. . ^ -.-. -r|r^-, .0 '"""'"'"-i l~S*alof ~dOPUNTIIO INSTRUCTICf8 -lF RS MD8L St no.

ThIsnetroet is lfive-bend radio rocetier with built in

i P..u fer4.stu ndurdisatiod so that the outpt ater willdirectly ldicato the voltage applied to the input terminals. TheOtpat t coversarac g of 1 to 1000 icrovoltl on a logarithmicscal. Ahmed of the first tube is en attenuator which provide anaddedraIg of 100 times, input, or 100 to 100,0 miorovolts.TO M REAI FOR USI8

1. INteud the uantena to the full 41l and insert..t .. - r. 8et the band witch ktob arkd D,C,B,A,X,' to the baud con-MICROVOLTS talning the desired frequency of easuresot.

S. Set the tuni dial to the desired frequency.4. Turn theb batterly witch to tho Qg position.

a S. For carrier eauren e to set the tole switch at the FIMi;!,;EmsTIAIIT position; for sersurements of irregular wave forms, suchas radio nolo , et the toggle sitch at the aRDIO OI0 position.s

4 1. Set the seloetor switch ton NAiJ nod adjustkhobpN ADtto sake ester read near uark ''IN AD'T. (This setting-is notoritic l; if the ttor radesanherbletwo the 'BRAT LWLIITmark ad the W AJ murk, the output ofthe calibr2tor wM z be

p/ I.foreseeei cre. Advance switch to IN tCAL nd wpose enter butto on k nobIMCROVOLTS *PR]8 AND TURN PRM ZEBS 8T', turning this knob to mkseator reed

S. Refer to curve at left, deteruinitn correct value of cealbrat-Fig. 4. Forerunner of all RFI measuring instruments Ing voltage for tlhe fruency ofe assuretth. Bye e of knoba rked CALIBRTi , aeun tri ndicate this value in microvolts.

4. Frees butto and roest neroi recheck gain as in B.

L. With Iater seletor switch at BLALt, voltage applied atineput d eoon black, 1 to ltorscall.P. If voltage exceeds 1000 uv, advne switch at 'RD' and read

on red, 100 to betO,Q)pr, scale.o02 0e S. For field inteneity inl icrovolts per meter, the eater read-ICROVOLT ingo most be divided by the antes effective height of J eotor.If eaxi accuracy is desired, headphone or other connections

should be renoved and the bo kpt at least three fet ay froI~ HI the instrouest and Antonag. The instruient should be set on level

groud wall in the clear of surroundin wires, trs, bnildings, t.4. ehook eotor sero occesionally.6. In continuous wave easuremaemt check the tning of the re-eiver occasionally; tole for eaiRm3 deflection.

(a)~~~~~~~~~~~~~~ US9E AS A VOLTkMET-2In the above, the intruent was considered as a field

masuring devie, using an exploring antona to pock up a voltag-which wee inpressed upon the teruinale of tho eater. It ean lao0 e ge tobe used a to-terinal voltter at sa frequenc in its rangby connectingthe voltage to be measured to the input torminal

RIOO/VOLTS through the R Antenna (Modl -1. The output eter wllindicate directly the microvolts applied at the tuned frequency,provided it as boeen made rea ad olibrated a outlined above.,The apacitance of the case tow e deis law eilo to permitmoearements of balaned circuit. if proper ieolation preautionsare observed

With theo msutr selector witch set at the positions 'A BATrsad 5 uAT-, theo output tor becResvoltnaterreading thevolth of thee betteries. Redings below the 'BAT LOW LIMIT'mark call for bttery replacemet.

MICROVOLTS

: dS INSTRUMET COmaRPOTnIO Boonton, lew Jersay U.S.A.

Fig. 6. Operating instructions, Ferris Model 32.

ments, using their military nomenclatures, is as follows:

AN/URM-3 150 kHz-40 MHz;~~~(a) ~AN/PRM-1 150 kHz-20 MHz;

AN/URM-6 15-150 kHz;AN/URM-7 20-400 MHz;TS-587/U 20-400 MHz;AN/URM-28 40-1000 MHz;AN/URM-29 40-1000 MHz;AN/TRM-4 150-1000 MHz;AN/URM-17 400-1000 MHz;Each of these instruments, when made available to non-

government purchasers, carried a different identification. Forinstance, the AN/URM-3 became the Empire Devices ModelNF-105.

V. THE FUTUREThe future of EMC will afford many opportunities to carry

out the original objectives of the IRE PGRFI, namely: to dis-seminate information on RF interference, to make recom-mendations on RFI measurements and reduction, and to serveboth group members and society.

(b) I foresee increased emphasis on EMC in the medical andFig. 5. Ferris Model 32B. (a) Front view, cover removed. (b) Addi- biological fields-learning more about the effects of electro-

tional view. magnetic energy on living organisms, the further use of electro-

THOMAS: EMC TWENTY-FIVE YEARS AGO 137

(a) (b)Fig. 7. External sinewave calibrator. (a) Ferris Model 32XA5. (b) Plug-

ged into top of RF noise meter.

UHF RADIO NOISE & FIELD STRENGTH METERModel 58

· Light weight, compact for port-able use.

* Built-in a.c. and d.c. power supply.· Self-.ontained calibration circuit.· Large hand-calibrated frequencyand microvolt scales.

· Push-button switching.

SIICIRCATIONS.Frequeney Range: 15 to 150 megacyleein five hands.FrTnqney Accuracy: Dials directly cal-brated in megacycles to an accuracy of± 25.Input Voltage Range: 1 to 100.000microvots in the antenna. 1 to 100microvolts on semi-logarithmic outputwith ratios of 10, 100 and 1000 ahead

FREQUENCY RANGE: 15 Me. TO 150 Mc. of .1 tube.Gain Standardilation: Internal "shot

TELEVISION: For the measurement of field s trength. signal-to- noise" diode provides calibration stand-ard. Special dial eliminates need fornoise ratios, noise levels. etc. The Model 68 is designed in accord- ar d

ance with the recommendations of the R. M. A. Sub-Committe onerf televiMion i8terwerence t w o tuned R.F. amplifier eliminates image

FREQUENCY MODULATION: The pas-band is wide enough to respon

permit accurate field strength measurements of frequency modu- down.lated signals down to level of a few microvolt per meter. ower pdPower Supply: Built-in regulated dualAMPLITUDE MODULATION, FACSIMILIE. etc.: The Model 65 power supply for operation from either

117 volta AC (70 watts) or 6 volts DC.is recommended for accurate measurements of any ultra high Step-down transformer available forfrequency carrier in the range of the instrument. 220 volts, 60 cycle operation.

Standard Equipment: Power cables, 15IGNITION NOISE MEASUREMENTS: Two important features foot antenna cable, 9 inch loop antenna,of the Model b8 for this work are the width of the pa-band and carrying strap and instruction book.the time constants of the weighting circuits. Measurements closely Dimanalea: 9" high a 18" wide a 11"approaching the peak values and hence the true nuisance value of deep overall.ignition and other pulse-type noise can be made. Weight: Approuimatly 3 pounds.DIATHERMY INTERFERENCE: The width of the pass-band of Tuba: 8-7W7 1-SJ71--..X6GT 1--966the Model 58 makes possible measurements on wobbly dithermy I-6J6GT 2-6AK5signals and harmonics which often cause more serious interference I-6Y6G 1-M74than the fundamental. 1--6H6

MEASUREMENTS CORPORATION

BOONTON NEW JERS5Y

Fig. 8. Measurements Corporation Model 58 UHF radio noise meter.

magnetic energy in vehicles of all types without the disasterous nition of the RF spectrum as a vital part of our environmenteffects of electromagnetic interference, the control of interfer- and positive steps to reduce to acceptable levels the electro-ence to and from computers and home appliances, and recog- magnetic pollution that presently plagues us.