HP 416A - Calibration (Less than 100% Reflection, Broadband)

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{ 4) T h is i s whe re th e trace norm ally begins , an d thi s p 01 nt cor ..
r e sponds to 8. 2. kmc. A s the dial is turned in t he fre que n c r
0
•
i ncre a sing d irect ion { cl o c kw i se ), the spot w ill tra. ··e rse th e
S C: !. ' e t::n . By stopp i 11 g the dial fo r e xa 111ple a t 8. 6, 9. 0, 9. 4:
9. 8, a nd 10 krnc in t u rn, a nd at the point at wh ic h th e s po t
stops ma rkin g the fr equency on the screen pl a te w i th a. gr ea s e
pe nci l, th e t:.. : a c e rnay be ca l ib rat ed .
9. Accuracy -
So c ali br at e d , me a su : rern e nt s of reflection coeffi cie nts wi ll be a c c ura te
wi thin ±5 %, ±0. 0 1. Accuracy obtained is a function of the re fl ec t ion
coefficient of the load being measured, as indicated in Fig . 10.
Most of th e er ror ov er the ba nd wi ll show up either as ripp le
0
or c ur v a-
ture 7 and, as indicated in Fi g. 10, error will be far greater at 1 00 %
calibration than at the reflection coefficient to be measured .
Calibration (Les s than 1 00% Re fl ection, B roadband ) --
Wher e low reflectio n coefficients a re to be measured, the Mod el 416A m ay
be c al i br a te d to le ss th a n 100 % b' .- usi rnr a lo a d whic h nr ese nts a known :refl e c t io n
of less than l 0 0%. The Setup p r~cedu r ~ is the s~me ~s that which prec e de s c a li -
brating to 100%. Calibration proc ed ur e follows.
l . On th e M o de l 67 0H M O s . ::: :i ll ato r:
a. Set the frequency-limit i ng stops for the desir ed range.
b. Check th at the SELECTOR s w itch i s at the MANUAL po s iti o n.
2. Disconnect the load, a nd replace it wi th a precision load wi th a kn ov m
reflection co eff icie nt. The H e wle tt-P a c kard Model X916 s e r i es of
Stand ar d Refl e ctio n s a re a v-- a il ab le f or u se with wa v egui de s ystE.:rn s
ope rating i n th e X b a nd . For purposes of this dis c us s ion, a l o ad w it h
a
10% reflect i on ( Model X 916C Standard Reflection } is u s ed .
Connect a Mode l X 9 16C to the outpu t of the re fl ect e d d irec t io na l c u u.p l 1 ~:r.
3. While manua lly s w eeping the Model 670HM oscill a tor, ad.just th e A TTEN f J" A ·
TION:co ;1 trol o ; .< th e l\/I od '3l 67 0HM, a nd w atch the t u ning e ye on t he 1v1od el
416A. Adjust the ATTEN UA TI ON co ntro l to obtain, ove:r t he frequ en c y
range , appro xirn.ately a n 1/8
1
'
ga p in the tuning e ye shutte r •
4 .
On t he lv 1o d el 67 0HM, se t th e S ELECTO R s w itc h at S WEEP .
5. On the M od el 416A:
a. Set the RANGE s wi tch a t the - 2 0 DB 10 % pos ition .
(6 ], [7] See Factors Which A ff e ct Accuracy of Reflectometer M ea sur e men ts , below.
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