HP 416A - Slotted Lines; Equipment

,,
'
Slotted Lines - -
General - The magnitude of the reflection coefficie nt of a load may be
ascertained by measuring the standing-wave ratio and applying the formula
i +I p I
i - I P I
SWR, where I f I is the magn itude of the reflection coefficient.
Techniques which may be used in mea suring standing wave ratios, pos ~
sible sources of error, and general precaution s to be observed in setting up
and operating a slotted-line system are d isc ussed in texts such as Terman &:
Pettit ' s Electronic Measurements and i'n instruction literature on slotted-line
sections such as the Hewlett - Packard Model 806B Coaxial Slotted Section .
Instructions given in this section are limited to those which are spe-
cific to the use of a Model 416A in a slotted~line system.
Equipment - A typical assembly of devices for measuring standing-
wave ratios, using the Model 416A Ratio Meter as the indicator, is shown in
Fig. 16 . Such a slotted - line system should i nclude :
A
source (with modulating capabilities) ·of signals
in the frequency range in which standing - wave ratios
are to be rneasured
0
Accurate , stable signal genera-
tors such as Hewlett - Packard Models 612A, 614A,
616A , 618B and 620A are suitableo Or a Model 670
SHF Oscillator and Mod el 717A Klystron Power Supply
may be used as a signal sourceo
A dire c tional coupler and a square - law detectoro In
the 2.6-kmc to 18.0 - kmc range
9
a high - directiv it y
series of couplers such as the Hewlett - Packard Model
752 Directional Coupler series is suita ble, The asso-
ciated detector may be either a barretter or crystal
detector 0 For the 8. 2 -kmc to 12 0 4 - kmc range, a
Hewle tt- Packard Model X421A Cry s tal Detector Mount
is available" and for the 2. 6 - kmc to 3
0
95 - kmc range ,
the barretter -eq uipp ed Model S485A Waveguide . Detecto ~ · ,
, . ' "-' · · _. ,lj.;
Moun t is availableo While t hes e excellent, higli - qu;ility
detectors ar~ recon1.mended, satisfactory perf ormance,
in gerrer i3.l' ;' '
1
M the ratio meter may be obtaine d when
other crystal d.etectors are used in the referenc e channel.
NOTE : It is to be noted , however, that for accurate indication
by the Model 416A , the detector in the probe c hannel
must be a high-q uality. true - square - law d evice.
A slotted - line section . A suitable low - reflection waveguide
slotted - line section m ay be a s sembled by using a Hewlett -
Packard Model 809B Un iversal Probe Carriage, Model 810
Waveguide Slotted Se ction, and ei ther a Model 444A Untuned
Probe or a Model 440A Detector Mount fitted with a Model 442B
Broadband Probe.
- 38 -