quirements specify testing over a wider temperature range. Measurements made in temperatures outside these limits may be accepted, provided the EUT, radio noise meters, all indicating devices, and equipment are at the testing location sufficiently long that their temperature become stabilized with respect to the temperature of the testing location. Evidence shall be given so that the calibrations of the measuring instruments used are accurate at the temperatures at which they are used.

4.7 Arrangements of EUT (on Test Site)

The EUT shall be arranged to the extent practical in a manner which simulates actual use, with the several units placed as nearly as possible in the worst-case setup found in preliminary tests per paragraph 4.2.5. An EUT which is normally operated on a table shall be placed on a non-conducting table having a height of 1 meter above test site ground level. For ease of testing, the table may be placed on a rotatable platform, in which case the total height of the table plus the platform shall be approximately 1 meter above test site ground level. If the platform is elevated, it should be nonconducting to the maximum extent practicable. In the event that all the units or peripherals of an EUT system will not fit on the table, one or more of these may be placed on non-conductive shelves below the table top, using the minimum spacing below the top for their placement. In selecting units for placement on the shelf, first preference should be given to those normally not requiring frequent attention.

For an EUT normally placed on the floor, the equipment should, if practicable, be placed on a rotatable platform. If the platform is elevated it should be non-conducting to the maximum extent practicable and have a height of not more than 0.5 meters above ground level.

The EUT shall be located in the center of the platform. If the EUT consists of two or more units, these shall be arranged around the center of the platform consistent with actual use, placed as nearly as possible in the worst-case setup found in preliminary test per paragraph 4.2.5.

Power and signal distribution, grounding, interconnecting cables and physical placement of the units should simulate as nearly as possible typical application and use. Starting with the worst-case setup found in paragraph 4.2.5 the arrangement of units and interconnecting cables should be varied (within the range of positions likely to occur in actual use) to maximize the strength of the strongest emission of those present (using data from the paragraph 4.2.5. tests as guidance). A sufficient number of arrangements shall be investigated to insure that the maximum radiation is measured.

The horizontal distance between the measuring set antenna and the EUT shall be measured from the closest point of the device or system, as determined by the boundary defined by an imaginary straight line periphery describing a simple geometric configuration enclosing the EUT system. All intra-system cables and connecting devices shall be included within this boundary. Excess length of cables shall be bundled at the approximate center of each cable by folding back and forth so as to form a bundle not exceeding 30 cm to 40 cm in length. For a Class B computing device, radiation measurements may be made at any distance between 3 and 10 meters provided the results are extrapolated to 3 meters using the inverse distance linear relationship; for a Class A computing device radiation measurements may be made at any distance between 3 and 30 meters and the data extrapolated to 30 meters using the inverse distance linear relationship. (See 6.2)

For an EUT located at the user's premises, measurements should be made at the appropriate limit distance measured horizontally from the boundary described by an imagi nary straight line periphery describing a simple geometric boundary that encompasses all EUT units. All EUT units and connecting cabling should be within the boundary. Where measurements at the greater limit distance (e.g., 30 meters) are impracti cal, measurements may be made at lesser distance (e.g., 3 or 10 meters) and extrapolated to 30 meters according to the inverse distance linear relationship.

A ground screen is desirable, but not mandatory. It is pointed out, however, that open field sites are likely to need a ground screen to meet the quality standards contemplated in FCC Docket 21371 to be set forth in Part 2, Subpart J of the FCC Rules, when any of the following conditions exist at the site: the terrain is discontinuous, the terrain is subject to extreme seasonal variations in ground conductivity; there are unburied power or control cables; the site is located on pavement.

4.8.1 Testing at User's Installation (OnPremise Testing)

A ground plane need not be installed for testing at a user's installation unless it is to be a permanent part of the installation. If a ground plane is used, it shall be electrically bonded to the utility ground as specified in 4.8.

5.0 Conducted Powerline Measurements

Unless otherwise specified, measurements shall be made to determine the line-toground radio noise voltage which is conducted from the EUT power-input terminals that are directly connected to a public

power network. The measurements are to be made with the EUT connected to such network thru a nominal, standardized RF impedance, which is to be provided by a lineimpedance stabilization network. A network must be inserted in series with each currentcarrying conductor in the EUT power cord. NOTE: It is recommended that conducted powerline measurements be made before measurements of radiated emissions, because this procedure is carried on indoors, requires rather little time as compared to radiation measurements, and can give some assurance that the shielding of the EUT is reasonably effective (at least at the lower frequencies).

5.1 Conducted Powerline Test Configurations

The EUT shall be placed at least 40 centimeters from an earth grounded conducting surface approximately 2 meters square unless it is floor standing and shall be kept at least 80 centimeters from any other earthed conducting surface. If the measurement is made in a shielded enclosure, the distance of 40 centimeters may be referred to one of the walls of the enclosure.

If the EUT is supplied without a flexible power lead, it shall be placed at a distance of 80 centimeters from the LISN's (or mains outlet where LISN's cannot be used) and connected thereto by a lead of length not greater than 1 meter.

If the EUT is supplied with a flexible lead, the voltage shall be measured at the plug end of the lead. The length of the lead in excess of the 80 centimeters separating the EUT from the LISN's (or mains outlet where LISN's cannot be used) shall be folded back and forth so as to form a bundle not exceeding 30 to 40 centimeters in length.

If the EUT is normally operated in the hand, measurements shall be made as if it is normally operated while placed on a table or desk. Measurements of power line conducted emanations are not required for devices capable of being operated only from internal batteries. If the EUT is fitted with a connection for operation directly or via separate transformer or power supply from public utility lines, measurements of power line conducted emanations shall be made.

When computing devices or their peripherals have their own provision for connection to a power line, line conducted tests must be performed separately for each device.

5.2 Line Probe

A line probe may be used for voltage measurements under certain conditions (see 5.6). If an appropriate LISN which satisfies the impedance requirements of Figure 2, having the current capacity of the EUT is not commercially available, the method

shown in Figure 4 may be used. The measurements should be made between each current-carrying conductor in the supply mains and the ground conductor with a blocking capacitor C and a resistor such that the total resistance between line and ground is 1500 ohms. Since the line probe attenuates the radio noise voltage, appropriate calibration factors must be added to the measured values. Measurement results with the appropriate LISN shall take precedence over the method shown in Figure 4.

5.3 Line-Impedance Stabilization Network A line-impedance stabilization network (LISN) having an impedance characteristic within the limits shown in Figure 2 is required for conducted radio noise measurements. Figure 3 shows a network which will provide the specified impedance over the frequency range 0.45-30 MHz. A coaxialtype connector shall be provided for connection of the measuring instrumentation by means of a 50-ohm terminating resistance across the 1000-ohm resistor. Provisions shall be made for electrically bonding the LISN enclosure to the ground plane used (see 4.8). If a direct bond is not possible, for instance with concrete floors, a metal sheet approximately 2 meters square shall be placed under the LISN and electrically bonded to the LISN by a short low impedance connection.

NOTE: LISN's designed to comply with the impedance characteristic of Figure 2 are not yet readily available on the market. As an interim measure, 5 microhenry LISN's may be used, provided that the readings obtained using these networks are increased by adding a correction to obtain a value equivalent to that which would have resulted had a 50 microhenry network been used in the measurement. This correction varies from +10 dB at 450 kHz to 0 dB at 2 MHz; values for frequencies between these limits may be obtained by reference to Figure 5. No correction is required above 2 MHz. This correction is based upon the relative impedance values of the 50 and 5 microhenry LISN networks in the range 450 kHz-30 MHz, and a presumption that the source of the EUT power conductors in this range is low as compared to that of the networks.

5.4 Grounding

The LISN housing, measuring instrumentation case, ground plane, etc., shall be electrically bonded together in such a manner that they are at the same RF potential.

5.5 Measurement Procedure

Measurements of powerline conducted radio noise shall be expressed as the voltage developed across the 50-ohm port terminated by a 50-ohm measuring instrument. All voltage measurements shall be made at the plug end of the EUT power cord, e.g., by the

use of mating plugs and receptacles on the EUT and LISN.

5.5.1 EUT Power Leads

All EUT input power leads, except ground leads, shall individually be connected through LISN's to the input power source. All unused 50-ohm connectors of the LISN's shall be resistively terminated in 50-ohms when not connected to the measuring instrument.

5.5.2 Shielded Power Leads

Equipment normally used with unshielded power leads shall be connected to the LISN and tested with unshielded leads. If the EUT is normally operated with shielded or armored leads, the tests shall be made using such leads.

5.6 Conducted Emission Tests at User's Installation (On-Premises Testing)

Testing for powerline conducted radionoise is permitted at the user's installation site, provided that no disturbance to the normal EUT installation exists, except to make provisions for connection of the 1500ohm line probe specified in 5.2 and Figure 4. Special precautions must be taken to establish a reference ground for the measurements. No LISN shall be used. The measurements are dependent on the impedance presented by the supply mains and may vary with time and location due to variations in the supply-mains impedance. (It may be necessary to perform repeated measurements over a suitable period of time to determine the variation in measured values. The time period should be sufficient to cover all significant variations due to operating conditions at the installation.) Such measurement results should be regarded as unique to that EUT and installation environment.

6.0 Radiated-Emission Measurements

Measurements of radiated radio-noise shall be made using the measuring instrumentation and antennae specified in 4.2 and 4.2.4, respectively. Radiation from the EUT including radiation from all signal and power cabling shall be measured. Consistent with Section 4, above, the EUT shall be set up and operated in a manner representative of actual use.

6.1 Determination of Test Radial

Radiated emission magnitudes shall be obtained in the azimuthal direction of maximum field strength for each predominate emission.

It is preferable to rotate the EUT to determine the direction of maximum field strength. A turntable arrangement may be used for convenience.

For large, heavy, and stationary electric equipment not readily rotated, the measuring instrument and test antenna may be moved around the EUT at as many points as

are necessary to determine the direction of maximum field strength for each predominate emission. Parties making measurements on test sites where the EUT is not rotated should understand that the minimum clearances for a test site with rotatable platform are not applicable; instead, the minimum clearance distance for a test site without a platform is changed to a circular area centered on the EUT location and having a diameter of 3 times the maximum distance between the measuring set antenna and closest point of the EUT.

Whether the EUT is to be tested on a test site with a turntable or is to be left fixed with the measurement antenna moved around it, it is suggested that preliminary tests be made, preferably indoors rather than on the test site, to determine the system spectrum signature, the strengths of the stronger emissions, and the directions in which these emerge from the system. During this testing, EUT arrangement should be varied within the scope of expect ed usage to maximize radiation. As provided in paragraph 4.5.3, if lengths of interconnecting cables may vary, tests should be made with one set each of the shortest and longest cables expected to be used, with excess cable length bundled. Using this experimental data as a guide for EUT arrangement, measurements then may be made on the test site. Where the EUT is not rotated on the site, measurements should be made of the strength of each of the emissions noted in the preliminary tests in the azimuthal direction determined in those tests. 6.2 Radiated Radio Noise Tests

Radiated radio noise measurements shall be made at one of the test sites described in 4.1, above. An EUT subject to a radiated limit at 3 meters, shall be measured at a distance of 3 meters, unless impractical be cause of size of the equipment, location, etc., in which case measurements may be made at a further distance up to 30 meters and the results extrapolated inwards utiliz ing an inverse distance extrapolation factor (i.e., 20 dB/decade). Equipment subject to a limit at 30 meters may be measured at a distance of from 3 to 30 meters provided that the results are extrapolated to equivalent signal at 30 meters utilizing an inverse distance extrapolation factor (20 dB/decade). At test distances between 3 meters and 10 meters the antenna shall be varied in height between 1 meter and 4 meters above ground. to determine the maximum level of emis sions within this range. Beyond 10 meters, to find the maximum signal level the antenna height shall be varied between 2 and 6 meters above ground. Both horizontal and vertical orientation of the search antenna shall be employed and maximum values reported. For vertical polarization the bottom

end of the dipole shall be kept at least 25 cm above site ground per paragraph 4.2.4. At sites other than open field, it is permissible to replace continuous variation of antenna height with setting the antenna at one or more fixed heights, provided that it can be shown that equivalent results are obtained.

A typical test configuartion for open-field and alternative sites is shown in Figure 1. The LISN, installed for the powerline conducted radio-noise measurements, may be left in place for radiated emission tests.

6.2.1 Electromagnetic Field: 30 MHz to 1 GHz

Any equipment or device to which it is applicable shall be measured for radiated emissions from all units, cables, power lines and interconnecting wiring.

Antenna position in azimuth shall be varied during the measurement in order to determine maximum field strength. Measurement shall be made at the azimuth such that the maximum radiation levels will be detected.

The antenna(s) specified in 4.2.2, above, preferably shall be positioned at the specified distance from the EUT for the duration of this test. Other test distances may be used and data extrapolated to specified distance per paragraph 6.2. Tests shall be made in both the horizontal and vertical planes of polarization.

The area of maximum radiation from the EUT may be initially determined by scan

ning the power leads and the equipment using the radio noise meter in conjunction with a short electric field antenna at a closer distance.

For record keeping purposes only the maximum emanations observed during the tests need be recorded and maintained in the permanent record file.

6.3 Radiated Emission Tests at User's Installation (On-Premises Testing)

Testing of the installed EUT may be performed at the end-user's installation with the results generally regarded as unique to the EUT and installation environment. However, where testing has been accomplished at three or more representative locations, the results can be considered representative of all sites for purposes of determining compliance with emanation limits. If no detailed instructions are given in the individual equipment requirements, measurements shall be made to locate the radial of maximum emission at a distance 30 meters from the equipment being tested. Where measurements at the 30 meter distance from the EUT are impractical, measurements may be made at lesser distances and extrapolated to the 30 meter distance from the EUT. A LISN shall not be used for testing of the user's installation in order that the measured radio noise voltage be representative of the specific site. Preliminary measurements of EUT spectrum signature directions of radiation may be made per paragraph 6.1.