Barracuda Networks SP4 Instrukcja Użytkownika Pobierz pdf (Strona 61)

STEREO GENERATOR – MPX OUTPUT SIGNAL

ENG

Axel Technology srl

www.axeltechnology.com

25.3 MPX SIGNAL CALIBRATION – THE POST CLIPPER GAIN

The output MPX Composite signal is composed by:

• RDS signal (whenever present)

• Audio components (L+R and L-R spectrums)

• Pilot 19 kHz

RDS and PILOT are fixed (invariable) parts in the MPX signal, while Audio Components are variable ones.

To adjust MPX output level it is recommended to start with setting desired level for fixed components in the

MPX signal (Pilot and RDS) and then adjust the variable part (audio) to get 75 kHz peak deviation.

STEP 1

: Adjust Pilot signal level via the MPX_Pilot Menu (recommended value: – 20 dB),

STEP 2

: Adjust RDS signal level via the RDS Level menu (recommended value: –31.5 dB)

Pilot and RDS levels are expressed in Decibel (dB) with reference to the Reference Tone (500 Hz, 0 dB). If

this tone is related to a Fm 75 kHz deviation, Pilot will cause a 7.5 kHz deviation (–20dB) and RDS will cause

a 2 kHz deviation (–31.5 Db)

STEP 3

: Once Pilot and RDS signals have been calibrated, adjust audio component via Post Clipper Gain control until

the deviation hits 75 kHz reference :

The 100% modulation level (correspondent to 75 kHz with 0 dB Gain on MPX level control) is indicated by the second

point in the ‘highlighted’ Zone (see picture).

75 kHz

reference

The third point corresponds to a 80 kHz deviation with 0 dB Gain on MPX level control.

Higher modulation levels will cause WARNING LED lighting on the front panel

. That LED indicates a modulation level

exceeding 5 kHz the nominal one and/or a saturation on audio input stage.

STEP 4

: Adjust the overall to apply the desired amplification / attenuation factor to nominal MPX level achieved at the

Step 3.

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Barracuda Networks SP4 Instrukcja Użytkownika Strona 61