Series Method of Calibration

c i r c u i t s and the complete tuning unit are

Frequency

Minor component

Characteristic

(common name)

range

identical with those described in paragraph

4. In the series method of calibration, the

Localizes magnetic field 2 0 - 1 , 0 0 0

Magnetic field

mc.

components of rf energy

probe for

o u t p u t of impulse generator G701 is in-

over the frequency

tuning units

jected into the signal pickup device, so that

range of tuning units 2

2, 3, and 4.

t h e calibrating signal path is in series

through 4.

Localizes electric field

150 kc-1 ,000

E l e c t r i c field

with the incoming rf signal under measure-

components of rf energy m c .

probe.

m e n t into the main unit and tuning unit.

over the frequent y

range of tuning units 1

Note: When operating over the range from 150 kc

through 4.

to 30 mc (with tuning unit 1), the loop or vertical

a n t e n n a must be substituted for the discone an-

b. Coaxial Relay K701 and Six-Step Sig-

tenna.

nal Attenuator AT702.

a . Coupling To and From signal Pick-

(1) C o a x i a l relay K701. This relay is

up Device. Both the green color-coded and

e n e r g i z e d in the SERIES CAL &

the red color-coded rf cables are con-

O P E R A T E position of calibration

n e c t e d between the two front-panel jacks

switch S706. Under this condition,

( J 7 0 5 and J717) and the corresponding

t h e incoming rf signal is passed

jacks on the injection block. The output of

through a set of relay contacts to

impulse generator G701 is coupled through

the input signal attenuator

a set of contacts of deenergized coaxial

AT702.

r e l a y K702 and through the green color-

(2) S i x - s t e p signal attenuator AT702.

coded rf cable to the input of the injection

The cartridge-type a t t e n u a t o r

block. The calibrated signal is reduced in

functions identically with that

amplitude by a 20-db fixed attenuating net-

d e s c r i b e d in paragraph 3 C (4). The

w o r k , housed within the injection block,

output of the attenuator is coupled

before being coupled to the return path in

t h r o u g h terminal A2 of main unit

series with the rf incoming signal. (When

jack J701 to the corresponding ter-

o p e r a t i n g o v e r the frequency range of

minal of the mating tuning unit plug.

t u n i n g unit 1, either the loop or vertical

c. Tuning Unit and Indicating Circuits.

antenna is used as the signal pickup device;

The signal flow through the tuning unit and

both of these antennas have identical 20-db

i n d i c a t i n g circuits is identical with that

f i x e d attenuators housed within their

described in paragraph 3. The intensity of

bases.) The attenuated calibrated signal is

t h e incoming rf signal is read directly

coupled in series with the rf signal under

from the meter, and is added to the setting

measurement, through the red color-coded

of the SIGNAL ATTENUATOR DB control.

r f cable, to the SIGNAL INPUT jack on

For precise measurements, the loss in the

the main unit front panel.

30-foot length of rf cable is added to the

b. Signal Path. The path of the com-

c a l c u l a t i o n . I f the 500-ohm conductive

bined unkown-amplitude rf signal and the

c o u p l e r is used in the measurements, a

known-amplitude c a 1 i b r a t i n g signal

constant factor of 26-db must also be added

t h r o u g h the receiver section is identical

to the final calculation.

w i t h that described in paragraph 4. To

obtain a meter indication of the level of the

5. Series Method of Calibration

unknown signal, without the series addition

(fig. 3)

o f the calibrating signal, it is only nec-

Figure 3 is a block diagram which shows

essary to reenergize the impulse generator

t h e signal path when the discone (broad-

by setting IMPULSE GENERATOR DB

band) antenna is used as the signal pickup

ABOVE 1 V/MC ON-OFF switch S705 to

d e v i c e over the frequency range from 20

t h e OFF position. To obtain a meter in-

to 1,000 mc. The block diagram shows only

dication of the level of the calibrating sig-

the basic sections: the signal pickup device

n a l , it is best to reenergize the signal

and a portion of the circuits housed in the

source. If the signal source cannot be de-

main unit. The remainder of the main unit

e n e r g i z e d , an alternate procedure consists