SAE ARP 958 (Aerospace Recommended Practice) provides guidelines for:
It is widely referenced in aerospace manufacturing, especially for parts requiring strict thermal processing, such as landing gear, engine components, and structural fasteners. Compliance with ARP 958 helps suppliers meet Nadcap (National Aerospace and Defense Contractors Accreditation Program) requirements.
If you're unable to find a free version of SAE ARP 958, purchasing it directly from SAE or through an affiliated institution is often the most straightforward and legal way to access the document.
The SAE ARP 958 standard is a cornerstone for Electromagnetic Compatibility (EMC) testing, specifically defining how to calibrate antennas used for measuring radiated emissions. While the full document is a paid standard, technical papers and draft critiques provide insight into its critical role in aerospace and military electronics. Core Purpose: 1-Meter Calibration
The "ARP" stands for Aerospace Recommended Practice. Unlike many other standards that calibrate antennas for long distances (far-field), SAE ARP 958 focuses on near-field measurements at a one-meter separation.
Antenna Factor (AF): It defines the procedures for determining the AF, which is the ratio of the incident electric field to the voltage at the antenna connector.
Two-Antenna Method: Traditionally, it uses two identical antennas placed 1 meter apart to derive gain and AF.
Standards Integration: This calibration is essential for fulfilling requirements in major testing standards like: MIL-STD-461 (Military subsystems) RTCA/DO-160 (Commercial aircraft) CISPR 25 (Automotive electronics) Critical Evolution: Revision E
The latest discussions around the Draft E revision highlight a major shift in how dipole-type antennas are handled.
Polarization Requirements: The proposed revision requires separate AF calibrations for horizontal and vertical orientations for certain antennas.
Measurement Ripple: Research indicates that while ARP 958 methods are industry-standard, they can produce "ripple" in the calibration curve, potentially leading to 1–2 dB differences compared to other methods.
Impact on Results: These small dB variances can determine whether a device passes or fails a strict military compliance test. Technical Scope Primary Distance 1 meter (standardized for shielded room testing) Antennas Covered Biconical, log-periodic arrays, horns, and loop antennas Phase Center sae arp 958pdf free
Addresses the ambiguity of the "apparent center" of curvature in near-field waves Traceability
Provides the link to the International System of Units (SI) for EMC labs
đź’ˇ Key Takeaway: If you are testing hardware for the Department of Defense or commercial aviation, your antenna calibration must likely follow SAE ARP 958 to ensure the results are legally and technically valid. If you'd like, I can help you:
Compare ARP 958 with ANSI C63.5 (the other major calibration standard).
Find specific MIL-STD-461 test limits that rely on this calibration.
Locate technical papers that explain the math behind the "Two-Antenna Method."
Searching for a free PDF of SAE ARP 958 (Broadband Electromagnetic Interference Measurement Antennas) can be difficult because it is a protected technical standard. Typically, it must be purchased through official channels like the SAE International Website.
However, you can find substantial technical information or older drafts through the following resources:
Public Access Repositories: Occasionally, older versions or related technical papers that detail the SAE ARP 958 methodology are available for free viewing on sites like Scribd or research platforms like ResearchGate.
Government Documents: Because military standards like MIL-STD-461 reference ARP 958, government reports from agencies like NIST often include detailed descriptions of the calibration methods used in the standard.
Technical Presentations: Industry experts often share presentations that summarize the standard's requirements, such as the EMC Society Detroit presentation, which critiques the recent "E" revision. Summary of SAE ARP 958 such as landing gear
This standard outlines the calibration and checkout of EMI measurement antennas, specifically for use at a 1-meter distance in a shielded room. It is critical for compliance with military (MIL-STD-461) and commercial (RTCA/DO-160) testing. Key Methods Include: SAE ARP 958 - AEROSPACE RECOMMENDED PRACTICE
SAE ARP 958 is Aerospace Recommended Practice that outlines the standard calibration method for antennas used in electromagnetic interference (EMI) measurements
. It is the primary standard for calibrating antennas used in
military and aerospace electromagnetic compatibility (EMC) testing , specifically for measurements taken at a 1-metre distance Core Purpose and Application The document provides a standardized technique to determine Antenna Factors (AF)
for broadband antennas. While most antenna calibrations are performed in the "far field," SAE ARP 958 is unique because it focuses on near-field measurements Military Standards : It is essential for compliance with MIL-STD-461 (specifically RE102). Aerospace Standards : It is used for commercial aircraft testing under RTCA/DO-160 Section 21 Shielded Rooms
: The procedures are designed for use in shielded rooms, although the standard itself does not account for the specific characteristics or reflections of the room. Calibration Methodology The standard typically employs the Two-Antenna Method Three-Antenna Method
SAE ARP958 is a critical aerospace recommended practice that
establishes a standardized method for calibrating antennas used in Electromagnetic Interference (EMI) measurements
. It is primarily used to determine "Antenna Factors" for equipment testing at a distance of 1 meter in shielded rooms. SAE International Key Features of SAE ARP958
The SAE ARP 958 (Aerospace Recommended Practice) is a cornerstone standard used in electromagnetic compatibility (EMC) testing. It establishes the uniform method for calibrating antennas used to measure electromagnetic interference (EMI)Â . Key Purpose and Scope
Targeted Calibration: It specifically defines the "standard gain" and "antenna factor" (AF) for antennas used in military and aerospace EMI measurements, such as those required by MIL-STD-461Â . introduced significant changes
Measurement Distance: Unlike many commercial standards that use 3-meter or 10-meter distances, ARP 958 focuses on 1-meter separation between the transmitting and receiving antennas .
Frequency Coverage: It provides methodologies suitable for a wide range of frequencies, typically from 20 MHz to 40 GHz, covering loop, biconical, log-periodic, and horn antennas . Calibration Methodology
The standard typically employs the Two-Antenna Method or Three-Antenna Method to calculate the Antenna Factor:
Two-Antenna Method: Used when two identical antennas are available. The gain is derived by measuring the insertion loss between them .
Three-Antenna Method: Used when the antennas are not identical. By performing three separate measurements (A1-A2, A1-A3, A2-A3), the individual gain of each antenna can be algebraically determined . Key Formula: The Antenna Factor (AF) is expressed in
and is critical for converting the voltage measured by a receiver ( ) into actual electric field strength ( Latest Revision: ARP 958E (2021)
The most recent update, ARP 958 Revision E (released Sept 2021), introduced significant changes, including separate calibrations for horizontal and vertical antenna factors to account for polarization-specific environmental effects . How to Access the Standard
SAE standards are copyrighted and generally not available for free. You can find official copies and detailed technical summaries through the following channels:
Official Purchase: Available for download from the SAE International Website or the ANSI Webstore .
Technical Summaries: Research papers on ResearchGate often provide the underlying math and comparative analyses of the standard .
Antenna Data Sheets: Manufacturers like ETS-Lindgren provide manuals for antennas (e.g., Model 3148) that explicitly state their calibration follows SAE ARP 958Â .
The central premise of SAE ARP958 is Site Attenuation (SA). This is a measure of the loss in signal strength between a transmitting antenna and a receiving antenna placed on a test site.