INDIVIDUAL SOURCE OPERATION
3-16
Reverse power protection
Accidental application of power to an individual signal source’s RF OUTPUT socket trips the
reverse power protection circuit (RPP) and a menu similar to that shown in Fig. 3-9 below appears
with a flashing message.
B3900
RPP B
Reset
RPP B
Reset
B
Fig. 3-9 RPP tripped
Note that the protection circuit may be activated when a source is set to a high level and its RF
OUTPUT socket has no terminating load.
The protection circuit can be reset by pressing the
[RPP Reset]
key for the appropriate source after
having either removed the signal to the source or terminated the RF OUTPUT socket. The display
then returns to the menu in use at the time that the RPP was tripped. If
[RPP Reset]
is pressed
with the signal still applied, the RPP will trip again.
The maximum reverse power at the CONNECTION TO RADIO socket is 0.5 W.
Modulation selection
The carrier from each signal source can be amplitude, frequency or phase modulated from an
internal or external source. Additionally pulse modulation is available from an external source.
The internal modulation oscillator is capable of generating two tones simultaneously in one
modulation channel and has a frequency range of 0.01 Hz to 20 kHz.
Modulation modes
Each signal source has its own independent modulation facilities. The MOD I/O socket on each of
the signal sources allows an external modulation signal to be summed with the signals from the
internal oscillator. This allows up to three modulations to be available from each source; for
example, external FM with a combined internal AM1 and AM2.
Modulation source can be internal or external. If internal, the modulation can be the sum of two
signals (AM1 + AM2, FM1 + FM2 or
ϕ
M1 +
ϕ
M2), each of which can have its own
depth/deviation and modulation frequency.
The common carrier wave can be modulated by two different types of modulation, where one uses
an internal source and the other an external source. The internal source may be composed of two
signals. Allowed combinations are:
internal AM + external FM ; internal FM + external AM
internal AM + external
ϕ
M ; internal
ϕ
M + external AM
Note that pulse modulation may be selected for each signal source in addition to any normal
modulation combination.
