7110.65R

signal strength and course quality, and is free from
interference from other NAVAIDs on similar
frequencies (e.g., co-channel or adjacent-channel
interference). However, the SSV signal protection
does not include potential blockage from terrain or
obstructions. The SSV is principally intended for
off-route navigation, such as proceeding direct to or
from a VOR when not on a published instrument
procedure or route. Navigation on published
instrument procedures (e.g., approaches or depar
tures) or routes (e.g., Victor routes) may use
NAVAIDs outside of the SSV, when Extended
Service Volume (ESV) is approved, since adequate
signal strength, course quality, and freedom from
interference are verified by the FAA prior to the
publishing of the instrument procedure or route.
NOTE-
A conical area directly above the NAVAID is generally not
usable for navigation.

b. A NAVAID will have service volume restric

tions if it does not conform to signal strength and
course quality standards throughout the published
SSV. Service volume restrictions are first published
in Notices to Air Missions (NOTAMs) and then with
the alphabetical listing of the NAVAIDs in the Chart
Supplement. Service volume restrictions do not
generally apply to published instrument procedures
or routes unless published in NOTAMs for the
affected instrument procedure or route.
c. VOR/DME/TACAN Standard Service Volumes
(SSV).
1. The three original SSVs are shown in
FIG 1-1-1 and are designated with three classes of
NAVAIDs: Terminal (T), Low (L), and High (H). The
usable distance of the NAVAID depends on the
altitude Above the Transmitter Height (ATH) for
each class. The lower edge of the usable distance
when below 1,000 feet ATH is shown in FIG 1-1-2
for Terminal NAVAIDs and in FIG 1-1-3 for Low
and High NAVAIDs.

FIG 1-1-1

Original Standard Service Volumes

1-1-6

Navigation Aids