HP 416A - Page 31

b . Di sconne c t the ca ble from the REFLECTED/PROBE input connector.
T h i s sets up A condition of zero reflection.
6. On the O s ci .Ho s c ope:
Proceed as de scribed under Calibration , 100% Reflection, above, to
establish a z er o refle c tion reference line.
7. On the Model 416A:
a. Reconn :.:;ct the cable from the reflected detector to the TU D FLECTED/
PRO B E: i nput c onnector . By choice of terminating load, it i s known
that there now exists a condition of 10% reflection.
b. Adjust the S ET TO FULL SC ALE c ontrol on the Model 4 J 6A to ob-
tain a full - scale indication on the 100% scale (with the RANG E switch
at - 2 0 DB l 0% , a 1 Oo/o refle c tion will g iv e a full-scale ind icati on on
the 100% s cale).
NOTE : If a 1 00% indication ca nnot be obtained , it indicc 1- te s that
th ere i s a diff erence in th e rectification efficien c y of the
h vo d etector s , a nd th ~ t the de tector w i th the lower eff i ciency
is in t he reflected ch ~ m.nel. T her ef ore t he two det ec tors
sho uld be reve:;: s ed ;: .,_ s it i s desirable that the detector with
th e gr ea ter eff icie rn:y b e p l a ce d in th e refl e cted channe t .
(If th i;;: d iff;;;:r e: 1c e i n re cCJ :i cati on eff ic ie n c y b e t ,, veen th e:
t wo d et e ct o r s i s le ss than 6 db, su fficie nt gain can b e i n-
s erte d by the S ET TO FULL SC ALE control to compensate
for the d ifferen c e .}
The m e te r pointer will var y around the 100% mark on th e scale.
Proceed as de s cri b e d abo ve under 100% calibration to obta in the
b e st av erage s e tting oi SET TO FULL SC ALE . The M odel 416A
now is cali br ated f or th e m e asure m e nt of re fl ection c oeffici e nts.
8. On the Osci lloscope:
a. A wavy t race shou l d app ea r on the oscillo s cope.
b. Adjust th e vertica l a1 np li Ger gain c ontro l so that the trace is about
one in c h abo ve ce n ter.
The voltag e now applied t o the vertic al amplif ie r is a d-c voltage
proporti on a l to the r.oete x deflection at various fre quencies across
thd b a nd under '.:: o nd it:i.on s of 1 0% refl ection. Thus a full-scale
refer e nc e li ne is establishe d .
NO TE: Wh ere the rne a su r err 1e nt b ei ng m ade is to asc~ rtain that
th e refl ec tion c oe ff icie n t i s below a certain percent, as
in som e i ndustr ia l applicati ons , the p r ocedure described
a b ove i s useful f o r rn a s s test purposes. The Model 416A
i s ca Eb r at r:.; d t o th e 1 ippe x -li m it reflection coefficient, which
resu l ts in the e s t<: tb li shme n t of an upp er-li mit reference line
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