Cisco AIR-ANT2420V-N= Datasheet download pdf (Page 11)

Figure 6. Fresnel Zone

Based on both line-of-sight and Fresnel zone requirements, Table 3 provides a guideline on height requirements

for 2.4-GHz antennas as various distances. This refers to height above any obstacles located in the middle of the

RF path.

Table 3. Guideline on Height Requirements for 2.4-GHz Antennas

Wireless Link Distance (miles)

Approx. Value “F” (60% Fresnel

Zone) Ft. at 2.4 GHz

Approx. Value “C” (Earth

Curvature)

Value “H” (mounting Ht.) Ft.

with No Obstructions

115

150

A 10-dB fade margin is included for 2.4-GHz calculations, while the included 5-dB fade margin for 5-GHz

calculations is sufficient for dependable communications in all weather conditions. The distances given are only

theoretical and should only be used to determine the feasibility of a particular design.

In outdoor deployments, and as a rule or thumb, every increase of 6 dB will result in a doubling of the distance.

Likewise, a 6dB decrease will halve the distance. Shorter-cable runs and higher-gain antennas can make a

significant difference to the range. The following links provide range calculations for the outdoor mesh products:

●

Cisco Aironet 1550 Series: http://www.cisco.com/c/en/us/support/wireless/aironet-1550-series/products-

implementation-design-guides-list.html

●

Cisco Aironet 1530 Series: http://www.cisco.com/c/en/us/support/wireless/aironet-1530-series/products-

implementation-design-guides-list.html

Regulations

North America

Connectors

In 1985, the FCC enacted standards for the commercial use of spread-spectrum technology in the ISM frequency

bands. Spread spectrum is currently allowed in the 900-, 2400-, and 5200- MHz bands.

In 1989, the FCC drafted an amendment governing spread-spectrum systems in the unlicensed ISM band, and

Congress enacted this amendment into law in 1990. This amendment is commonly referred to as the “new rules” or

“’94 rules” because it impacts all spread-spectrum products manufactured after June 23, 1994. Products

manufactured before June 23, 1994, are not affected by the amendment.

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Cisco AIR-ANT2420V-N= Datasheet Page 11