Meinberg TCR511 - Manual (Page 11)

11
Input impedance
The IRIG-specification doesn’t define values for the output impedance of generators or
the input impedance of receivers. This fact led to incompatibility of some modules,
because the manufacturers could choose the impedances freely. For example: if the
output impedance of the generator is high and the input impedance of the receiver low,
the signal level at the receiver input might be too low for correct decoding. Therefore the
board TCR511 provides a jumper to select the impedance (50
Ω, 600 Ω or 5 kΩ) of the
input for modulated codes ( SMB ) to comply with the requirements of several systems.
Meinberg IRIG-generators have an output impedance of 50
Ω Ω Ω Ω Ω, to build a matched
transmission system when using a coaxial cable. If such a generator is used to synchroni-
ze TCR511, the input impedance has to be set to 50
Ω accordingly (default on delivery).
In addition to the telegram, the AFNOR-code defines the input/output impedances
also. If TCR511 is synchronized by this code, an input impedance 600
Ω Ω Ω Ω Ω of must be set.
The setting „5 k
Ω“ may be necessary if the generator has a high output impedance (see
specifications of manufacturer). The driver software shows a bar chart for evaluation of
the signal level at the receiver input.
The following detail of the place plan of TCR511 shows the possible jumper setting
with the related input impedance:
JP1 in position 1 - 50
JP1 in position 2 - 600
JP1 open - abt. 5k