FLAT

Flat response probes are the most common. Narda’s patented

RESPONSE

shaped frequency response probes read out in Percent of

OR SHAPED

Standard and are particularly useful in complex, multi-signal

FREQUENCY

environments where exposure limits are different for the various

RESPONSE

emitter frequencies and in classified environments.

SIZE AND

The majority of the 8700 series probes have four-inch (10 cm)

MINIMUM

diameter heads. The minimum measurement distance for

MEASUREMENT

these probes is about 4 inches (10 cm) from the outside surface

DISTANCE

of the probe. Measurements made at closer distances can

 

result in inaccurate readings due to capacitive coupling. The

 

Models 8721D, 8723D, and 8725D have two-inch (5 cm)

 

diameter heads that can be used as close as 2 inches (5 cm)

 

from the source to the outside of the probe. These probes are

 

ideal for the measurement of waveguide leaks. Similarly, the

 

Model 8781D has a one-inch (2.5 cm) diameter head with a

 

flexible shaft that is designed for locating leaks in densely

 

packaged microwave systems.

Shaped Frequency Response Probes

The goal in designing and manufacturing a traditional, “flat” frequency response probe is to make the probe equally responsive to energy at every frequency within its rated frequency range. In contrast, Narda’s patented shaped frequency response probes are designed and manufactured so that their sensitivity mirrors a particular standard as closely as possible. For example, many of the major standards in the world set limits for maximum exposure at the lowest frequencies of 100 mW/cm2. These same standards typically limit exposure in the VHF region to 1 mW/cm2 and to 5-10 mW/cm2 in the microwave region. A shaped frequency response probe designed for such a standard is 100 times more sensitive in the VHF region than at the lowest frequencies. The result is that energy from all sources within the probe’s rated frequency range are not only summed in terms of RMS power but are also weighted in direct proportion to a particular standard's frequency dependent exposure limits.

10

Operating the Meter