BSTJ 30: 4. October 1951: The Developmemt of Electron Tubes for a New Coaxial Tramsmission System. (Ford, G.T.; Walsh, E.J.)

11.3 MB·English

‘The Development of Blectron Tubes fot a Now Coaxial
‘Transmission System
By G.. FORD and FJ. WALA
(arene Ree Jl 2, 18)
1 Trnormeri
8 THE demand for long distance tlepione circuit has ineres,
aver teasaicon systems capable of ending wore lates pr

auctor have been developed, Alo the sdvene of fcevishns bas teal
enuand for bi! bara channels for netior fetes, One ofthe latest
Aevclopnents sow seri eorpletin i the L3 Casta! Systm.

Three ner tues have been developed speccally to met the exacting
regultements of Lit aystome Ho Teed, the WE. 438A end We, (268,
fn a rs, Ge WR ISTA, All tee types are used in the ine ad fi
fmpliiers. The new tubes make parnible « subetaataly higher lve of
Droud band amples petonman mpl to thin predosesne, They
repreeent the zeslt uf iuprivente me hy nppsing vel noo basic
pple throug nea Libemaking techie. There teckaiguse bave
inte deve lage within the feaenoak of exis ole
phn take manafactring methods.

‘The delenit of xe, sll, lw power vacuum tubes fo high fre
quency apeaton inthe Bell Sper: began in 108%, The tule programm
‘as ited originally a6 part of esearch pj the fe al
Communications. When the Hevelgament ofthe bl Conse Sytem Degas
St sas recognized that sinulartalux woul! Ie ese Dart oF the tbe
Alevelapmers ele ea Hotta ected loyal Ue eosin requtement,
Work on the Wok, 888 and WE, S8A tubes usd fn tie Lt ster
one ete h 9 as em outgzvrth of thls pogean

‘The demand for amplcation over wider Irequcey aus rele in
further evelopmerc work elong te sme Lines. During Wiel Wr IL
‘int ox applied to tae deveoesent of te GAR. ihe which became
Seale erly in 194 a was cl widely ia TF senile aa ecu
men, Story aller tye war che WE, 408A tube was develope! for tee
‘houe repeater uns, This in long Mle version of the @AAS tube vig
thse clecteal censure exo fr he hate vl ad cure
‘The Wi. 4044 tube eppeared in elope rei ie 190. The tae,
having 8 hipher agure of merit than the WR. MRA, provided improved
vesforennor in the IP anspler asd ia the New Vork tn Boston mio
Mo rm nner saaae rzeeaL joumeat, ocronux 1951

relay systom and in the TH2 taco slay system. The Wik. 486A, WE.
{3A and Ws, TVA sah ane te Lea Iypen to come out of ts long
range program,

TL wil be seen in what follows that the ey to continua development
slang these nes has bee itaproverent i the tenigues of gril making
to meet te base jective of proving grit which can be spaced very
‘get the cave al wie, nee, acts 23 unfory ysl plaze
Contelng he eneren én frm Ue cathode without ofering any pis
fal obstruction, Tai ubjective fe agreached by using many ths of very
Sinll diameter ie fr the grid wining. The zewsmn for the close gr
Cathode spacing i thet the teamennductance or sensitivity pes on this
Factor. Alay the incre fv input eapacitonee which reauls i 8
vantage bocce of its eects on the interstage crits, dis saan
Se mre than eampensitel fr by the bigher tmnsmeductence obtain

2. Panierens oF Dosen

21 Reguinoments

"The oveellropiements fo the 13 ys, and the masnner fn shih
they ate telaced To the tube paraseters re very compex. Lloever, i
ite nimplesttomos, the objelive forthe L$ sytem 5 t prove on we
fouls ppe a ‘ality suitable forthe simlinws teasmisson over a
{tonite ccuit of a elvis sgl ond 60 een’ telepione channel
fr, altentivey. 188) cae-vay telephone channels eho no elev
‘lane repr, The tratamscion hud ing provided fom aqpra
mately 0.3 MC tw eppuonimetely K MC. The aapiier need lo cumpen-
Sate forthe exile atesantion must meet very ext ny rmqearnts ith
Fespect to gndroquomry characteristics, stablity, nose and nest,

The deni futures nocss-y Ur puovde stable eect Lubes for we
in the Tampere ace coeey raced to the rqsiemets mentioned above
for the amplifiers Ia genem! tes, che tube design objectives ace: (1)
nigh tramennductancecapaciance rato (Ggure of ems}, (2 minim
rene phase chit or phase delay, (3 lw nen, (2) wel esatraled ma
uon, (long Fe, i) interchangable, are) lea cost consistent
withthe Sires sjetives, Ha the material whic follows, ench ofthese
Ghjetives ‘il Be dened in detall and its relaonsip to ue syst
objec brat ut

22 igure of Merit:

igure of merit eof partial importance. It sa diect mesure af the
bundeidth over which the vegured amplicatio can be obtained. Tn gen-
euernox runes 20m 4 Colom svermat 1105

ral a given factor af improvement inthe fice of merit cin be tansiased
directly into a wider unsmisson band providing more communicaLion
‘hannels

For two-termine! type af interstage auch that used in the LS ample
Ser, the gue af merit ie

Ka

op - Kee
BGs

a
wher Fi he igre of mei (Fhe vollage mpieaton, A eth bade
Sridth between the Tries chee the arin ey below that at th
Center Kroqueny, K ie a constant whose value depends on the particular
interstage deren, Ge the tremscandactance ofthe tube, Ce the Sapa

srecitanee, and Ce ithe ootpae capacitance, This figee of meric
recy applicable to setode opeaced as ¢ eal-signal voltage anpiier
ed io well nr elas.” It wil he ted to show Row te tube
‘lesign fetore inten che figite of ret of the WE. 5A and WE,
136A bes

Talng equate (1) and applying erin simplityng nsmptions which
can be mede without mately oti Une rel expressions ane de-
rived inthe opyendlx sowing the selaGinship Dtven the Gare of mer
and the tube parameters. Equations 2) and (1) inthe apple show bs
the figure of merit is aBectod by the grt spciny a" Ue el
secon =pacing°B", the seoencplae sseiig “at fhe sad wine caus
"See Fig, Equation 3 aves the roqived cceen vekage forthe as

6 PIERS AYR, ON Fup
110 rm maak susina vormeX, joumxaL, osronEK 19

sumed cuncat density and geomy. Singe these expressions a nather
involved, the seaanee in which te warn Caco inBueace the figure of
eri a rug Rest by eres of wn Figure 2, 3 aad how
ow Fe allecied by changes n "a "8", and "e".Figues 6 oo 7 show
how the seen voltage reel tn gel tne assumed curren density witha
iva bigs By pres ih a al 8" (uation) The scree welage is
CSauntaly incependen of 2"

‘These retiostijs ane alw apbeable to the W.R, ASTA tule with
nar wadisetons.

221 Design Comsierations
iow th vain factors in equations (2), (8), and (8) ect the figure
of mere wil be disarm eu. They a ein Table
The fastor AF ie the ratio of the [Sate eurrnt Co Cio cade current.
“The Lgue of ert iseinel' projet ote cor or be ine

+ ae
: Hee uaeecntes

hy ong ane wine Sa he eteen gud, che minim pretense
Teng tesmise by the mechanical rigiisy and heat sation one
Taisen ale be intend =p cedacing he nme of tart on
he dere, bo chi a inte the vest or slices hin elect
ome the zeeuzement cet tae pve gr cata eon a pein
Toa vue,

‘Since te lgan: nf rei tty propane tothe exe roo af te
cathode cures! versity fy, Ue inpneansat wit inteasing fy fe aot
Seay mpi The orblems af obtaining saiforr initia: performance ar
Tong iene aggre Iip ine te cutvent deni, for sever ee
ons There fe moet evento sun Ut igh eurent ensigy por a2
urceactelerated Ine of valle seein. In fst thee i rome
ine tea? Hore he Wage th prone

enw RE LE Wee § Wage
19686 TIMES FOR 4 ANTAT ETE 07

ally seine with high cue ensity edt shorten she ie, High
esto temperate, hier pei, al he pret ore iat
fare the major tts in this extegory, [tis prem thatthe shorter ile
Ton er sherri xe I the preter rae enantio of
the cathe

by miter Fon the ater jurts nf the he. Crest forts
have lies mtd od al Ly ate proceesig Lebesgue wih wl inc
‘nia his Kind fini atl ty oder taneiuent te the cathode
(thik wil counter t sch testi, The into atte tne the LS

or i
_ re

tubes wore being develop wok Ha SO MNJem was a high » eeomt
Ahersiy ss sosned co be consistent withthe lange mia

Tic apy om the cuwes i Pig 2 tha te igre meri nes
apily az te ed-eathde spring Yo" i reo. The ination eres
rrshaniel and tanifeets ies inf ware Ones the practi ial
‘tsar the parts 3 closely ith sient acrarey. The oer i the
robles seit i fbiestng gre wom with creo sal eno
‘Sener Uo make effective nse of the cue grilesthoe spacing. Th
tur uf the subject il be esc! imei le I oe of the ra
Enportent septs of the cesgn of the LS bes.
108 tm wxza. sxsEHMC MRoMINCAL yormAL, O=TOREE 1951

1 wold apts fora Fig, 3 that the gr aernn pcing °" shou be
ss lng a» posible, Ewever the equine seven Vatage iceeszs ss
increases, end i jx aie key Ure seen. voltage low. Therefore,

‘is uae es low as pcethlewil causing too nue penalty or. igure
‘of merit A god compromise value for °8" dopends on the range of got
fathode spacing "0" Being orcerl, lo it wil usualy be fom 6.005 cm
‘ea an for clase spaced tubes

Figure 4 shows that tho Sgure of merit increases aa “e™ increases, but
there Is very Title advantage in miking i more than 0.000050 cm,
‘Making imu Inger also inrenes the ose dimensions ofthe strace

ture vonecessils, and eventually leas to spacing whic wil cause i=
regulates in the pte cuenc pte voltage caracterstic due to space
‘harge eects iv Uns scant apace

Although i x ot sppaeat fous the cueves a fom what has Ben sid
hove its sirable to have "ns sll a posible, eis obs thst

sot be ee thin 2, others the grid is comply ow, ee

te seeumption tha! wr = 1 this mis hal“ mas hel th Sa
it tace to be open space between the grid wires Actually, itis deiable
to have not more than 30% oft projected aren of the grid closed which
Luvcrton ks woR A emis EE 1108

means that “should be fess Hn 11S, tlio to this consideration,
itis desirable to have r”romsideraly es an 0.154 chat the regu
scoan voltage wil be as low a8 possble This comes about becaose the
Smpiteaton Lalor inceeaes “PS inceseed, other quantities bd
forstint, al pation (3) shows that Boy incense a6 increase The
tingram shows ie Fig. 8 ilstestes the trl in grit spacys ae)
tril wine sas. The WE, 416A tube Gormerly BVT. 1888) repesets the

meg
ep
ia ne

~ Qa

Tig. $e in pase

retest tension of this tend eeported far 9x grl-cthoe ang
fencer?

"The dae of mest nceases ae the sata vale ol Ube bist Ey.
sauce since Ie inereazes mere, » minimum ia vale nf alaaat “13
Sle fs ually nocesury inorder to evel uadesizable eects due to the

Rt
110 ans wee

2 FRERNECAL YOUENAL, ScTOMEY 195

collection of eletone of high iia! wily ty the canted gid, Sued
id cartonts contributes the as,
‘uee excuse signs distortion
Sine increas asthe sre wllge o's ncensd, te gure of merit
liken incenss, Xia desible ory Fa la a sible fr atleast
tucereaons, The ios importants nat high sree votage wl generally
Ihave an adverse oct on be ie. Tie seca shat low power coneum=
tion i desirable for economic rant stl the hed ig tht it helps som.
the standpoint ot maining lw tensperatures of the components in an

pinning a ny alo

ample. Figur @ ad 7 show how Bis depends on “a! and 8", The
enucemant that Eye be kept low means that the range na al 3"
(ish eas be wee i etre,

‘The eects of electron trai law wal lead ielutance in the tubes
nus be takes into geeouet im ome Uo meet Ute smpliier equlenents
tvith eepet to ph min. [4 omer to maintain stable operation over
svernins Tuas som 4 COMME sxsitak rn

tn desir transnssion the yin and pe craic ou at
Controlled yp tv abet 200 MC. Tsuru ase ita he Cece
‘here che gin became ssi roa over psa" is pases itera.
Inve Lk cmpliter this Ire mney eae 40 MC. Phate i ated
by electron tint tie arly el flan ror ys ese
rags” ial of exe. the exces phe non bee

The ie oq orm hee ro toi scl le ate
is of the order of 10 "recone, Tak onnregone nat uf wasn
At 0 MC, Close spacings aa high eles pter ae tea! tp vale Uae

Ironsl ti, Homevér, the oaiertions dacs iv Sesthin 2.2 hove
sera te je aces iy the spans en ple ae ene the
earl tie Hoge Gar ee las eign mei

Ty ing fltively heavy lead wie abd mounting the tae tractor io
such a way as to nie te led wites as shore es posse the sk ho
fxcess phased to the led ite fins been mini that i ama

ste mang against 8 singing codon, the
ampliir basen cesigne to ve sbows AV lee pase sit at 40 MC
1112 rae nua sree emioes joumAt, OeTORER 1951

vith tse tubes than that which wil casse singing, With this situation,
{ean be aon that any substan foc of incense in the excess phase
Jinnuce by the tubes, amy otber components, al gin to veduce
the phice margin seriou

26 Hoi

luctention noe i as important factor in tho WG. ABSA ns inthe
fet sage heptane ai Sy Ee WA, 436A ged nthe fs sage
ofthe oni! arpir, Thr i adoguate margin gine she elec of ove
frequency noise components such a2 micrephonic, omer Iraguency har,
dhol "surier sniee” HE regonable proceilions in tbe sal cla dei
dre token. Fron sgh eeaaepoit, the Facto mie ni ened by
‘Aloping a subitadon of tht perature ad current Cran
felt dat, with a normally actve cath, te apace current Sula
ally space slauge imitod, with ample manga for some les of cae
sce inservice hone be Werperaane Lint ezaditin is approsched
‘When the tempeatne Unita ren 's reached, te naise is substantaly
ghee than for he spose chang Lusied cenciton. "The tperatare and
the unthte cares easily racage fr these tes have ten et #1 alee
tthich take thee vnniceratioe ate accuat.

28 Maaation

Since 4 maine purpose of sing soothe to uve the mulation
products aisng inthe nplib, the more neues at ideal Unease
fheracterstc can he aprmiche in the tube design tbe Betts, ecnoae
less feedback ie roqire lo wstain a yvea grade of system performance
Usfrtanasly, omroe, rnnvestonal tide 2 tetoe fyp0 9 venom
tube operating ner ween! sje charge Hints: crdtiors neteeely
Ins e inner chase tevsic whi ie abner, Severs! seeible special
sfroches which av ve les teodlater. were explo bl ie were
Thad shiv woul pri the eguied gure of meri: a be eel
lal an rel

‘Cousdesele emphasis we puss: Ue problans of conteaing the
‘aration fn nett ation fron Ife b's, Te ue naoreant factors ne
(eleceatiode spacing, wife of eid pice and cre activty, A
thigh theee fans de well cone for other reasons, the
special requirments on odaton reveitated a tncousa investigation,

"The eft uf tic graethoze acing caa be expressed in terms 0° the
Ee pnte cuenta te sgral vel For ae Raving an idealized