Potomac Instruments FIM-21 - General Description; Equipment Specifications

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SECTION l . GENER.AL DESCRIPTION
1.1
Scope of Manual
This manual provides a comprehe ns ive technical description of the
operating and physical characteristics of the FIM -2 1 and FIM-41 Field Strength
M eters. It provides sufficient information conc er ning the operation and func -
t
ional theory of operation to permit effective operation of these instruments.
1.2 Purpose of Equipment
Field Strength Meters, FIM - 2l and FIM-41 are light - weight portable
ins truments for the me asurements of a wide range of radio signal intensities
in the .54 to 5.0 MHz fr eq uency spectrwn. The FIM - 21 covers the broadcast band
(540 to 1600 KHz) while the FIM-41 covers the broadcast band and harmonic fre-
quencies to 5 .O MHz. Both units are rugged test instrumen ts that are equally
effective for interference studies at low signal strength and for close-in meas-
ur ements on high-power directional arrays. In addition , a special input jack
permits the receiver to be used as a null detector for RF Bridge measurements.
l.J Equipment Specifications
(See specifications, FIM-21, Table 1-1, FIM-41, Table 1-2)
Table l-l. S pec ifications: Type FIM-21 Field Strength Me ter
Frequency Range:
Fi eld Intensity Range:
Accuracy
of Calibration:
Accuracy of Range Attenuator:
Se l ectivity
B andwidth (6 db):
IF R ejection:
Image Rejection:
Adjacent Channel Re jection:
Panel Meter:
Antenna:
535 KHz to 1605 KHz
lO microvolts per meter to
10 volts per meter
1 percent, referenced to
NBS Standard Field
2 percent over entire FI range
and tuning band
7 KHz nominal with m ulti-pole
hybrid fi l ter .
1- 1
75 db minimum
80 db minimum
50 db minimum 10 KHz above and
below tuned station
4n mirrored scale, logarithmic
graduations l to 10, taut band
meter movement, 2% linearity
Shielded loop, integral part of
hinged cover