rf exposure

FCC ID: H25VXS250

RF Exposure Info

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FCCID_274137

H25VXS250

RF Exposure Statement:

The following statement will appear on page three of the Operator Guide.

RF EXPOSURE STATEMENT

In bodyworn deployments, when installed as directed, this
equipment complies with the FCC radiation exposure limits set
forth for an Occupational/Controlled environment. Only antennas
specifically designed and tested by DTC for on-body applications
should be used.
In General Population/Uncontrolled environments, proper
spacing must be maintained between the radiating surface of the
antenna and any person’s body. In the case of a simple dipole
antenna with (2.1 dBi gain), a minimum spacing of 2.5” must be
maintained. In the case of gain antennas up to (17dBi), a minimum
spacing of 12.5” must be maintained.

H25VXS250

Calculation Method of RF safety Distance:

The power density S, in mW/ cm2 is:

S = (P*G)/(4*Π*r2) (Eq. 1)

Rearranging and solving for distance yields:

r = √((P*G)/(4*Π*S)) (Eq. 2)

Where:
P = power input into the antenna in mW
S = allowable power density in mW/cm2
G = numeric gain of the antenna relative to an isotropic radiator
r = distance to center of radiation in cm

The limit for Maximum Permissible Exposure (MPE) for General Population/Uncontrolled Exposure in the
frequency band 2450 – 2500 MHz is 1.0 mW/cm2 (47 CFR 1.1310).

As shown in the Operators Guide, antennas intended for use with this device range in gain from 2.1 dBi to
17 dBi. The transmitter power is 250 mW.

For the 2.1 dBi gain antenna case, transmitter power = 250 mW, and substituting S = 1.0 mW/cm2 :

First convert the antenna gain from dB to numeric:

G = 10(2.1/10)
G = 1.62

Then substitute P, G, and S into Eq. 2 to solve for the minimum safety distance:

r = √((P*G)/(4*Π*S))
r = √((250 * 1.62)/(4*Π*1.0))
r = 5.6 cm OR 2.2 inches

So the safe minimum safe distance for a 2.1 dBi gain antenna is 2.2 inches.

For the 17 dBi gain antenna case, transmitter power = 250 mW, and substituting S = 1.0 mW/cm2 :

First convert the antenna gain from dB to numeric:

G = 10(17/10)
G = 50.1

Then substitute P, G, and S into Eq. 2 to solve for the minimum safety distance:

r = √((P*G)/(4*Π*S))
r = √((250 * 50.1)/(4*Π*1.0))
r = 31.6 cm OR 12.5 inches

So the safe minimum safe distance for a 17 dBi gain antenna is 12.5 inches.

Document Created: 2019-11-05 12:15:50
Document Modified: 2019-11-05 12:15:50

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