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Commands to set transmitter predistortion
< s e t i n t e r f a c e f s k 0 e q u a l i z e r c o m p e n s a t e { h i g h - p a s s | l o w -
p a s s } >
< s e t i n t e r f a c e f s k 0 e q u a l i z e r d i f f { 0 | 1 | 2 | 3 | 4 | 6 |
8 | 1 0 } >
It is necessary to determine which key frequency should be lowered and by what extent. To do this,
the two 500FSD20 modems can be configured as test transmitter and test receiver.
Commands to set test transmitter or test receiver
< s e t i n t e r f a c e f s k 0 e q u a l i z e r t e s t { o f f | r e c e i v e |
t r a n s m i t } >
2.9.9.1
Determining the transmitter predistortion
1 Set transmitter predistortion.
– In order to have a basis for assessing the measurement result, the first measurement should
be carried out with the predistortion switched off (0 dB).
< s e t i n t e r f a c e f s k 0 e q u a l i z e r d i f f 0 >
2 Set the transmitter and the receiver of the two 500FSD20 modems to the same bit rate and the
same channel (see Chapter 2.9.2, "Channel configuration"). The test is carried out in half-duplex
mode.
< s e t i n t e r f a c e f s k 0 { r x | t x } b a u d r a t e { ... } >
< s e t i n t e r f a c e f s k 0 { r x | t x } d e v i a t i o n { ... } >
3 The following settings should be done for the duration of the test:
< s e t i n t e r f a c e f s k 0 r x z e r o 1 >
< s e t i n t e r f a c e f s k 0 r x i n c r e a s e - d e t e c t 0 >
< s e t i n t e r f a c e f s k 0 d u p l e x >
< s e t i n t e r f a c e f s k 0 n o s q - e v a l u a t i o n >
< s e t i n t e r f a c e f s k 0 { r x | t x } s e l e c t i v i t y h i g h >
< s e t i n t e r f a c e f s k 0 e q u a l i z e r t e s t { r e c e i v e | t r a n s m i t } >
4 Examine whether the DCD LED on the test receiver TR is flickering:
– YES = receiver is being influenced by crosstalk or faults from other channels. This problem
can be remedied by reducing the receiver sensitivity. Maybe the transmission level can be
raised appropriately. However, it is then possible that adjacent channels will be influenced.
– NO = o.k. No influence from any adjacent channels.
5 Issue the command < s e t i n t e r f a c e f s k 0 e q u a l i z e r t e s t t r a n s m i t > on
the test transmitter (TT). The TT starts a test sequence (lasting for 4 to 32 seconds depending
on the bit rate).
6 The test receiver (TR) evaluates the sequence immediately and displays the result in the form
of a flash frequency. The LEDs flash for approx. one minute at this frequency. In order to display
the result on the test transmitter, the TR transmits the flash frequency to the TT, where it is
displayed as a flash sequence by the RxD LED.
– The RxD LED is flashing on the TT.
– The EQZ LED is flashing on the TR.
– Flash frequency: 0 to approx. 25 Hz
– 0 Hz = best result
– 25 Hz = worst result
26
Functions
1KGT151043 V001 1
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