Special Publication

---

Due to the frequency dependency of the Fresnel zone
calculation, migration to a higher frequency band may
require antenna height adjustment. Figure 11 displays
Fresnel zone spacing for operating at 1920 MHz and
shows that if the original 2 GHz path was designed with
antenna heights to have a full first Fresnel zone clear-
ance (noted as 1.0 F1), at the obstruction, it would
have excessive clearance at the 6.5 GHz band (between
F3 and F4). Space diversity antennas/equipment will not
correct for this problem.

It is important to re-evaluate the Fresnel zone clearances
for each path to eliminate excess clearance. Some
paths may require lowering antenna height adjustments.



Figure 11 - System Performance, Fresnel Zone Clearance

---

Andrew Corporation
10500 W. 153rd Street Orland Park, IL U.S.A. 60462

PR-20-01 12 March 1993

---

Page 7 of 11 -- Page 8 of 11 -- Page 9 of 11