HP 11757B Посібник - Сторінка 9
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Digital Radio Testing
1-6
Error pulse input variable threshold is only available
in serial prexes 3235A and above.
5. The display next reads
need to set this unless you are planning to use the
ALARM INPUT for this test. Press the
advance to the next feature.
6. The display should read
PRESET scale factor is 1.0, and this should only be
changed if your BERT's error output is sending out
error pulses at a rate other than it is detecting them.
For instance, if the error output of your BERT is
sending one pulse for every four errors, set the scale
factor to four. To set the SCALE FACTOR press
when
4 ENTER 5
3 SCALE FACT
the
arrow key to display the factor your want,
485
then press
again.
4 ENTER 5
7. The display should now read
(Automatic Gain Control) maintains the power level
of the spectrum sent through the Fader. You may
want the power level to remain constant even though
a notch is sweeping through the band. If you are
interrupting the digital radio after its own internal
ALC or AGC circuitry, you may have to use the
Fader's internal AGC circuitry to prevent non-fade
eects from distorting measurement results. Press
, then use the
4 ENTER 5
AGC OFF is displayed. Press
8. The display should now read
AGC is ON, you should ensure that you have the
proper AGC center frequency set. Press
and the display will change \
whatever frequency may have been set previously.
Use the arrow or data keys to set the desired
frequency, then press
9. The display should now read \
allows you to set the bandwidth to distribute the
HP 11757B
. You will not
2 ALARM POL
485
. The
3 SCALE FACT
is displayed, then use
4 AGC ON/OFF
key to display AGC ON if
485
to exit.
4 ENTER 5
. If the
5 AGC FREQ
4 ENTER 5
AGC FRQ 070.0
.
4 ENTER 5
". This
6 AGC BW
key to
. AGC
" or