Tektronix 454A - Page 33

B A N D W I DT H - BE A M F I N D ER swi t ch i s p r esse d d ow n , t h e
d i s p l ay i s com p r esse d wi t h i n t h e g r at i c u l e a r ea . To l ocat e
a nd r e p osi t i o n an over sca nn ed d i s p l ay, u se t h e f ol l owi ng
p
r oce du r e :
1 . Pr ess t h e BANDWI DTH- BEAM F I N D ER
swi t c h
d own .
2 . Wh i l e t h e BANDWI DTH- BEAM F I N D ER swi t c h i s
h el d d ow n , i ncr ease t he ver t i cal a nd h or i zo n t al d ef l ect i o n
f act or s u nt i l t h e ver t i cal d ef l ect i o n i s r e d uce d t o a b out
t h r ee d i vi si ons a nd t h e h or i zo n t al def l ect i on i s r e d u ce d t o
a b out f our d i vi si o n s ( t h e h or i zont al def l ect i on nee d s t o b e
r e d u ce d onl y w h e n i n t h ezyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA § - ¥ mode of o p er at i o n ) .
3 .
A dj ust t he ver t i cal an d hor i zon t al p
osi t i o
n
co
n
t r ol s
t o ce n t er t h e d i spl ay a b o u t t h e ver t i cal an d h or i zont al
cen t er l i n es .
4 . R el ease t h e BANDWI DTH- BEAM F I N D ER swi t ch ;
t h e d i s p l ay s h o u l d r emai n wi t h i n t h e vi ewi ng ar ea .
B an d wi d t h L i mi t er
T
h e
BANDWI DTH- BEAM F I ND ER swi t c h pr ovi d es ±
met h od of r e du ci ng i nt er f e r
ence f r om un want e d h i g h -
f r e q ue n cy si gnal s w h en vi ewi ng
l ow- f r equency
si gnal s
. I n
t h e FULL p osi t i on, t h e f u l l ba nd wi d t h ca pa b i l i t i es of t h e
V
er t i cal Def l ect i on syst em ar e avai l a b l e . Wh e n set t o t h e 20
MH z p osi t i on ( up) , t h e upp er - 3 dB b a ndwi d t h p oi nt of
t h e V er t i cal
Def l ect i on syst em i s l i m i t e d t o a bo u t 20 mega-
V er t i cal C h annel Sel ect i on
O p er at i ng I n st r u ct i ons- 454 ‘ / R 454A
h er t z . T h en u n wa n t e d h i g h - f r e qu en cy si gnal s
( s u c h as t el e-

Fi g . 2 ± . ( ‘ ) CRT di spl ay
s
h
owi
ng h i g
h - f r e qu ency i n t er f e r ence w h e n
at t e mp t i n g t o vi ew ™¿É - ™
e
½
e1
1
¿É - f
r
equ en cy si g · ± 1 ( ’ ) r es u l t a n t , ,
vi si on b r oa d cast r a d i at i o n i n t er f er e n ce) a r e r ed u ce d i n t h
e

d i spay y whe n B AN D" ™Å¤™ i ’ “ ‘ œ F I N
DER s w i t c h i s set t o 2¿
-
d i s p l ayed wavef o r m .

F i g . 2- 7

i l l u st r at es t h e u se of t h i s

MH z posi t i on .
f eat u
r
e . T h e wavef or m i n F i g . 2- 7 ‘ i s t h e d i spl ay p r oduce d
w h e n ±
l ow- l evel , l ow- f r equency si gnal i s vi ewe d i n t h e
p r esence of st r o n g 50- mega h
er t z
r a d
i at i on ( BANDWI DTH-
BEAM F I ND ER swi t c h i n FULL p osi t i on) . F i g . 2- 7
’ s h ows
t he r es u l t a n t C R T d i s p l ay w h e n t h e h i g h - f r e q u ency i n t er -

t h e I NPU T connect or of t h e c h a nn
el use d . T h e ver t i cal
f er ence i s r e d u ce d by set t i ng t h e BANDWI DTH- BEAM

d ef l ect i o n s h oul d be exact l y f i ve d i vi si o n s . I f n
ot , ad j u st t h e
F I ND ER swi t c h t o t h e 20 M H z posi t i on .

f r o
n t - p a n el GAI N ad j ust ment f o r exact l y f i ve d i vi si ons of
def l ect i o n .
E i t h er of t h e i n p ut c h a n nel s can b e used f or si ngl e- t r ace

NOTE
di s p l ays .
Appl y t
h
e si gnal t o t he d esi r ed I NPU T co nn ect or

i f
t h
e gai n of t he t wo c h annel s must be
cl osel y
and set t h e M OD E swi t ch t o d i spl ay
t h e c h a nn el used .

mat ched ( suc
h
as f or ADD mo d e o p er at i on) , t h
e
H owever , si n ce C H 1 O NL Y t r i gger i n g i s pr ovi d
ed onl y i n

ad j u st ment pr oce dur
e gi ven i n t h e Cal i br at i on sect i on
C h an n el 1 a nd t h e I NVER T f eat ur e i s p r ovi d ed
onl y i n

s h ou l d be u se d .
C
h
annel 2, t h e cor r ect cha n nel must be sel ect e d t o t a
k
e
a d vant age of
t
h
ese f eat u r es . F or d ual - t r ace d i s p l ays,
con n ect t h e si gnal s t o bot h I
NPU T co n nect or s a nd set t h e

T h e b est meas u r eme n t acc u r acy w h
en usi ng p r obes i s
M OD E swi t ch t o one of t h e d ual - t r ace p
osi t i ons .

pr ovi de d i f
t h e GAI N ad j u st ment i s ma d e wi t h
t h e p r o b es
i n st al l e d ( set t h e
VO L TS/ DI V swi t c h t o 20 m V ) .
T h i s
V er t i cal Gai n
Ad j ust ment

compensat es
f or
any i
n accur aci es of t h e p r ob es . Al so, t o
pr ovi d e t he most acc u r at e meas
u r ement s, cal i br at e t h e
To chec k t h e gai n
of ei t h er c h an n el , set t h e V O L TS/ DI V  ver t i cal gai n of
t h e 454 ‘ at t h e t em p er at u r es at w
h i c h t h e
swi t c h t o . 2 and connect t h e 1 V CA L ™ kH z
connect or t o

measur ement i s t o b e ma d e .