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4100 Field Strength Meter
PI 4100
Medium Wave Field
Strength Meter


The PI 4100 is Potomac's third generation of precision survey instrumentation intended for the direct measurement of electromagnetic field strength in the 520 kHz to 5.1 MHz frequency spectrum. This instrument combines a laboratory quality radio frequency voltmeter, a calibrated, Balanced Loop antenna, an internal GPS receiver, an internal calibration source, and data acquisition hardware and software in a single rugged package weighing less than 3 kg.

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Main Screen Display
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Spectrum Display
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This device is equipped with an embedded microcontroller engine that obtains measurement data from the various transducers within the instrument and formats that data for display and, at the option of the use, stores it to memory.


The PI-4100 was designed to become the successor to the industry standard FIM- 41 and to provide the accuracy and reliability that the international engineering community, government regulators, and broadcast licensees have depended on for more than a generation.

PI 4100 innovations include:

127 dB dynamic range measuring receiver
Digitally synthesized tuning in 1.0 kHz increments
Spectrum Display to facilitate various compliance measurements (Field
Strength, Harmonic level, and Spectrum Occupancy) in a single instrument
Provisions for third party calibration, using their own laboratory standards,
when it is impractical to return the instrument to the manufacturer for
Data acquisition software and PC interface to enable the collection,
analysis, and e-distribution of field measurements. (This feature anticipates the future acceptance of data e-filing by federal regulatory agencies.)

Various I/O ports have been provided to enhance the versatility of the instrument and to perform certain operational tasks such as battery recharge and computer data exchange.

Rear View
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RF Inputs
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Aux Inputs
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   Published Field Reports

     Icon"Potomac FIM-4100 Field Report", Radio Magazine

     Icon"PI 4100 Takes to the Field", Radio World

Field Strength Meter
  Frequency Range 520 kHz to 5.1 MHz, calibrated
  Field Strength Range 22 µV/M to 50 V/M (27 dBuV/m) to
154 dBuV/m)
  Measurement Uncertainty 3.0% (±0.3 dB) referenced to NIST*, standard field
     Measurement Bandwidth
     Adjacent Channel Rejection
     Image Rejection
     Spurious Rejection

1.0 kHz
>85 dB at ±9 kHz
>60 dB
>80 dB
  Minimum Frequency Step 1.0 kHz
  Self generated 2nd & 3rd harmonics <-85 dBc (carrier F/S <10 V/M, from 530 to 1700 kHz)
  Antenna Type

Balanced, multiturn Loop (removeable)
RF Voltmeter
  Electrical specifications shown above
RF Signal is applied directly to RF In BNC
  Measurement Units

µV-mV-V; mV only; dBuV/m
Spectrum Display
  Center Frequency Range 520 kHz to 5.1 MHz
  Frequency Span ±63 kHz, ±22 kHz
  Resolution Bandwidth

1 kHz

Data Storage & Retrieval
  Measurement Points 250 max.
  Download Software PI Proprietary (Microsoft Excel® format compatible)
  Download Format

ASCII: Comma Delimited

I/O Ports
  Headphone Jack 3.5 mm Stereo Audio Jack
  Battery Charging Jack (12-15 Vdc) 2.1 mm Power Jack (Switchcraft 722A or equiv.)
  Data output / Control Input Jack USB Type B (for bi-directional computer interface)
  External RF Calibration Jack BNC (provides for calibration by a 3rd party cal. lab.)
  External RF Input Jack BNC (input impedance 1890 ohm +12pF) provides for antenna signal injection
  External RF Output Jack BNC (50 ohms) RF output is proportional to Field Strength
  Batteries (AA cells, six required) Rechargeable; NiMH (supplied)
(can also use 1.5V: Alkaline or Lithium)
  Battery Life 5 Hrs. Minimum before Recharge (NiMH)
  Battery Recharge Time 3 to 4 Hours
  Operating Temperature Range °C(°F) -15°C to +50°C (+5°F to +130°F)
  Dimensions cm (inches) 38x18x28 cm (15x7x11 in.)
  Weight kg (lbs.) 2.5 (5.5)

* Specifications subject to change without notice.

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4100 Field Strength Meter

Click for Full Instrument View

Salient Features:
  • Lightweight, Rugged & Portable
  • Accurate & Versatile
  • Self Calibrating & Easy to Operate
  • Digital Tuning
  • Digital Field Strength Display
  • Digital Spectrum Display
  • Digital Data Capture & Storage
  • SBAS augmented GPS positioning
  • E-Data Friendly Transport Software
  • Useable, 200 kHz - 8500 kHz
  • DRM Capable
  • Harmonics Measured to 5.1 MHz
  • Uncalibrated FS to 600 V/m
  • Antenna Orientation Compass
  • Use Hand-held or Tripod mount
  • Calibration Traceable to: NIST *
  • External 50 ohm Calibration Input Port
  • RF Output for external Spectrum analyzer
  • DC Output of dBuV/m
  • Removeable Loop Antenna
  • Shielded Modular Construction
  • Built-in Quality and Reliability by: Potomac Instruments, inc.
  * US National Institute of Standards and Technology