Radyne OM20 Specifications download pdf (Page 53)

OM20 Universal Outdoor Modem OM20 Theory of Operation

MN-OM20– Revision 5 4–15

4.7.3 EXT REF: External Reference, Optional

The External Clock connector is optional and must be requested at time of order. This is not

actually a clock, but does have some clocking implications. When the external reference is used,

the master oscillator within the modem is locked to the external reference, and the internal

accuracy and stability of the unit assumes that of the External Reference. Therefore, not only are

the transmit frequencies locked to the external reference, but the modem’s internal SCT Oscillator

is locked to the external reference as well.

External reference port input is specified at

.1Vpp to 5Vpp (Sine or Square wave)

4.8 RS422/V.35 Interface J3 (Standard option)

Data must be clocked into the modem by either the SCTE or SCT Source. If SCTE is selected as

the Tx Clock Source, then SCTE must be supplied to the modem on the EIA-530 port. The output

of the dejitter buffer will be clocked with this source. SCT should be used if SCTE has excessive

jitter.

4.8.1 G.703 Interface (Optional)

G7103 is an optional interface option. The G703 option supports both balanced and unbalanced

interface types. he modem support If the G.703 Interface is selected, then the Tx Clock Source

will default to SCTE and the Clock Polarity will default to Auto.

Loop timing with a G.703 Interface or Asymmetrical Data Rates requires external equipment at

the remote end that is capable of using the recovered RD Clock as source timing for (SCTE) SD.

The modem will not manipulate the clock frequency. Therefore, the transmit and receive clock

rates must be equal in order for the modem to perform loop timing.

4.8.2 Ethernet Data Interface J4 (Optional)

The modem support a 4 port 10/100 Base-T or a 10/100/1000 Base T Interface. When this

interface is selected additional menus will be displayed. Refer to Appendix J for interface set up

and description of supporting features.

When Ethernet Data Interface is selected, the Tx Clock Source will default to SCTE and the

Clock Polarity will default to Normal. In addition, the Buffer Clock will default to RxSat and the

Buffer Clock Polarity will default to Normal.

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Radyne OM20 Specifications Page 53