Subcarrier Injection Level; Setting Subcarrier Amplitude - DEVA Broadcast SmartGen Micro Maintenance And Operation Instruction Manual

Basic rds/rbds encoder with usb connectivity

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Quick user manual (4 pages)

Table Of Contents

Table of Contents

In the sidechain mode of operation, the RDS subcarrier is the only signal that appears at the

rear-panel RDS OR MPX OUTPUT connector. Because some exciters require a high signal level at

auxiliary wideband (SCA) inputs, the RDS signal has been made adjustable to any value between

0 and 3192 mV p-p.

In loop-through operation of the encoder, the composite/MPX program signal that is fed to

the PILOT OR MPX INPUT appears with unity gain at the RDS OR MPX OUTPUT. A typical

peak-to-peak level of the Composite/MPX program signal is up to 10dBu. The same 0-4V RDS

subcarrier level range is available in this mode.

SETTING SUBCARRIER AMPLITUDE

Many FM modulation monitors are not capable of making an independent measurement of

RDS subcarrier injection level. For this the monitor requires a special subcarrier measurement

filter centered at 57kHz. Taking certain limitations into account, however, nearly any conventional

mod-monitor may be used to set RDS injection with reasonable accuracy, although this requires

a temporary interruption of the audio program... perhaps best done during a maintenance period.

Here is the procedure:

1. With the SmartGen Micro encoder disconnected from the exciter, check that the mod-monitor

shows total carrier modulation at the accepted 100% figure for program peaks.

2. Disconnect the stereo generator and any SCA or other subcarrier generator from the exciter.

Do make sure, however, that the stereo-gen continues to feed a composite/MPX signal to the

SmartGen Micro MPX IN connector.

3. Turn the RDS LEVEL control on the rear panel of the SmartGen Micro fully counterclockwise,

and then connect the RDS OUT of the SmartGen Micro to a spare wideband subcarrier input of the

exciter. As the mod-monitor is downranged to its most sensitive scale, only system noise should be

indicated, and at a negligible level if at all.

4. Slowly advance the RDS LEVEL control clockwise. The mod-monitor will begin to register

the RDS subcarrier. Set this to the desired injection level, typically 3.5% of total peak modulation

(see the following note).

NOTE:

Many mod-monitors change from a peak to an averaging response on the more

sensitive scales in order to present a more meaningful measurement of system noise. Check the

manufacturer's documentation to verify the measurement response of your mod-monitor on lower

ranges. If response indeed proves to be averaging, the indicated RDS injection will actually be

about 4dB lower than the peak value. Consequently, set injection for an indicated 2.2% (with

averaging response); this will equate to the desired peak deviation of 3.5%.

5. Reconnect the stereo-gen and any SCA or other subcarrier sources to the exciter. You may

now note a very slight increase in total modulation on program peaks. To maintain RDS and any

other subcarriers at their proper injection relationship, the output of the stereo generator (i.e.: the

audio program level) may have to be turned down slightly so that total modulation is once again

at the desired modulation limit.

NOTE:

The SmartGen Micro encoder will have been programmed with default RDS data at

the factory to confirm operation prior to its shipment. Be sure to enter you own RDS data before

placing the SmartGen Micro into actual service.