Operating instructions

LOCAL OPERATION

3-46

Off

Disables any active distortion measuring function and removes the distortion bar chart from the

display.

Hint. By disabling this function, the time taken to measure the remainder of the measurement functions is

shortened thereby reducing the update time.

S/N

Selects Signal to noise ratio as the measurement method. Compares the level of the demodulated

signal together with the system noise, against the level of the system noise only, using the

formula:-

S/N

= 20

log

20 log

()S

See Fig. 3-10 a & d, Distortion level and signal to noise level measurements, on page 3-36. The

distortion bar chart is graduated in dB and is also displayed as a digital read-out above the bar

chart. The Rx test menu is recalled automatically after pressing this key.

SINAD

Selects SINAD as the measurement method. The modulation generator is set to 1 kHz. By

filtering the demodulated signal with a 1 kHz notch filter and comparing the result with the

unfiltered signal, the SINAD level is established using the formula:-

SINAD

= 20

log

20 log

()

See Fig. 3-10 a, b, & c, Distortion level and signal to noise level measurements, on page 3-36.

The distortion bar chart is graduated in dB and the SINAD level is displayed as a digital readout

above the bar chart. The Rx test menu is recalled automatically after pressing this key.

Dist’n

Selects distortion percentage as the measurement method. The modulation generator is set to

1 kHz. By filtering the demodulated signal with a 1 kHz notch filter and comparing the result with

the unfiltered signal, the distortion percentage level is established by the formula:-

Distortion

= 100

100

()

SND

See Fig. 3-10 a, b, & c, Distortion level and signal to noise level measurements, on page 3-36.

The distortion bar chart is graduated in % and the distortion percentage level is displayed as a

digital readout above the bar chart. The RX TEST menu is recalled automatically after pressing

this key.