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(I)

Figure

VSWR introduced in a flat line by the insertion

of a Type 874-GAL Adjustable Attenuator.

SPECIFICATIONS

A waveguide-below-cutoff type, useful as a calibrated

attenuator or as a sampling device. Calibrated in decibels,

on a micrometer-type scale.

Absolute attenuation is the

sum of insertion loss and scale reading.

Phase shift is

essentially constant as attenuation is varied. The main line

is a short coaxial section with locking GR874 connectors,

one end for source, the other for load.

It introduces mini-

mum discontinuity when inserted in a 50-ohm line.

The

loop output is brought out through three feet of 50-ohm

cable with locking GR874 connector.
Calibrated Range: 120 dB (relative attenuation) with input

line terminated in 50 0; 129 dB with input line terminated

in adjustable stub to minimize the electric field at the

coupling point (scale reads —9 to 120 dB).
Insertion Loss (from input connector to end of output cable

at 1 GHz, when signal source impedance is 50 0):

With input line terminated in 50 0, and scale set at 0 dB,

30.4 dB ±2dB; set at —9 dB, 17 ±2dB (settings below 0
are not accurate).

With input line terminated in adjustable stub (Which ex-

tends the range over which the calibration is accurate to

the —9 dB scale setting), 19 ±2dB minimum.

(Insertion loss is approximately inversely proportional to

frequency up to 1 GHz.)
Insertion Loss Directly Through Tee: Negligible.
Accuracy of Attenuation:

Stub-terminated input, ±(0.0l times difference in attenu-

ation r0.2) dB, direct-reading.

50-U terminated input, ±(0.015times difference in atten-

uation r0.2) dB, when corrected. Correction chart

supplied.
VSWR Introduced into Line: <1.03 at 1 GHz; <1.12 from 1
to 4 GHz.
VSWR of Output: <4 at 1 GHz; <5 from 1 to 4GHZ.
Max Power: Input power limit inversely

proportional to

square root of frequency. Power should not exceed 300

at 1 GHz. Output power should not exceed

1/2

Patent No. 2,548,457.

GENERAL RADIO COMPANY

*WEST

CONCORD,

MASSACHUSETTS

01781

FREQUENCY.

GHZ

8 74.0.13

Form No. 0874.0210-I

6/68

Printed in U.S.A.

Содержание 874-GAL

Страница 1: ...cations the maximum usable attenuation is limited by leakage from various parts of the driving circuit and not by the range of the atten uator In this type of variable attenuator as the attenuation is varied the phase at the output connection is essentially constant with respect to the input signal phase The method of coupling to the coaxial line permits the attenuator to be used as a standard cal...

Страница 2: ...ase the special correction given in Fig ure 2 is required and in addition the frequency correction of Figure 3 is required In the second configuration recommended to achieve the best accuracy above 2 GHz the termination is an adjustable stub employed to place a voltage minimum at the coupling points The frequency correction graph of Figure 3 is required only in this case The detailed procedure is ...

Страница 3: ...attenuation is accurate at scale readings as low as 9 dB and at frequencies between 1500 and 4000 MHz readings above 0 dB on the calibrated scale are accurate if the stub is set as previously outlined An alternate method of setting a voltage minimum at the coupling point f or frequencies above 1500MHz utilizes the fact that the attenuation constant for the desired mode is smaller than that of the ...

Страница 4: ...loss in the line 2 The attenuator can also be used to measure the attenuation of a network by the substitution method as indicated by the block diagram in Figure 6 Readings of the detector output and attenuator setting are first made without the circuit under test connected The circuit is then inserted and the Type 874 GAL Adjustable Attenuator is readjusted to give the same detector indication Th...

Страница 5: ... H TYPE 874 GAL L H t j i1Jl J111 L When source Is connected to end of at tenuator marked S subtract correction labeled NORMAL from reading For t opposite connection add REVERSED a correction ft it t 1I I II II 10 0 0 20 30 40 ATTENUATOR READING A dB 50 60 874 0 12 Figure 2 Correction chart for use with Type 874 GAL Adjustable Attenuator when exciting line is terminated in its characteristic imped...

Страница 6: ...005 0 00 Actual AttenuatIon 1 K a Indicated AttenuatIon 1000 2000 3000 4000 FREQUENCY MHz Figure 3 Frequency Correction Factor Figure 4 VSWR seen looking back into output con nector of a typical Type 874 GAL Ad justable Attenuator FREQUENCY GHz 874 G 8 6 GENERAL RADIO ...

Страница 7: ...e attenuation of a network TYPE 874 R22LA PATCH CORD 1209 5 Figure 5 Block diagram of a simple signal generator using the adjustable attenuator and other GR874 Coaxial Elements TYPE 874 D2OL OR D5OL 874 G 14A TEST TYPE 874 GAL ADJUSTABLE ATTENUATOR 7 ...

Страница 8: ...or to end of output cable at 1 GHz when signal source impedance is 50 0 With input line terminated in 50 0 and scale set at 0 dB 30 4 dB 2dB set at 9 dB 17 2dB settings below 0 are not accurate With input line terminated in adjustable stub Which ex tends the range over which the calibration is accurate to the 9 dB scale setting 19 2dB minimum Insertion loss is approximately inversely proportional ...

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