R.V.R. Elettronica HC4, User Manual

Page: 20 / 72

HC4
16 / 34 User Manual Rev. 1.0L - 01/04/02
5.3.7 Versions menu
This menu shows the hardware (H.V.) and software versions (S.V.) of the machine.
5.3.8 Protection sistem
The protection system implemented in hybrid coupler is based on two types of
reactions, the “Foldback” and the temporary disabling.
5.3.8.1 Foldback
The foldback circuit controls the level of a dc voltage that is available on the
dedicated BNC connector (F.BACK) on the rear of the HC4.
The foldback voltage remains approximately constant until one of the amounts
that are connected to the foldback doesn’t surpass its nominal value (full scale).
When this happens, the foldback voltage is rised proportionally to the amount the
threshold is surpassed, and a yellow LED is lit on the front panel, signalling the
intervention of the circuit. In figure, X represents one of the variables connected to
the foldback, X
0
is the full scale of the variable, V
FB
is the voltage present on the
BNC:
X
V
FB
X
0
In the HC4, the variables connected to the foldback are:
• Forward power
• Reflected power
• Rejected power
• Temperature
The foldback voltage can be used by the transmitter’s exciter to reduce accordingly
the driving power. For example, RVR Elettronica’s PTX-LCD is designed to use an
external foldback signal of this kind.