Specifications

SG-231 MANUAL
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After RF is applied to the coupler array, it then passes through the detector system. The
detector system consists of seven capacitors in shunt on the input arm of the network,
nine inductors in the series arm, and six more capacitors in shunt on the output arm, all
arranged in binary increments. Relays are provided in conjunction with each lumped
constant and allow removal or entry as desired. A network having 128 values on input
shunt C, 64 values of output shunt C, and up to 512 values of series L is possible with
the manipulation of these 23 relays.
7.3 Impedance Detector
RF transformers T1 and T2 drive the impedance bridge that is balanced at 50 ohms. T2
samples the line current and thus D4 outputs a negative DC level proportional to line
current. A tertiary winding on transformer T1 provides a line voltage sample to D9
which provides a positive voltage proportional to line voltage. R35 and R36 act as a
summing network for the current and voltage signals, with ratios chosen, such that at
50 ohms, the summed signals result in a balanced or zero voltage condition.
If the line impedance goes to high, the signal from the voltage sensor will be relatively
higher than the current sensor, which will result in a net positive output voltage from
the summing network. Similarly, a low line impedance will result in more output from
the current sensor, resulting in a net negative output voltage from the summing
network. The summing network output is shifted to a 0 to 5v range, then fed to the
processor's A to D converter ports, and used within the micro-controller.
7.4 VSWR Detector
A directional coupler is made up of a current transformer T3 and a voltage transformer
T1, in conjunction with termination resistors R17 and R18. The coupler is inserted in the
50-ohm transmission line between the input connector, J6, and the tuning network. The
forward power is measured across termination R18 and reflected power is measured
across termination R17. Diode D3 generates a positive DC voltage proportional to
forward power and D8 generates a positive DC voltage proportional to reflected power.
The forward DC output is fed to a voltage divider consisting of R45 and R34. These
voltages are input to the RF power detector and to an A to D converter port of the
processor. The reflected DC output passes through a voltage divider consisting of R39
and R40, and then it also goes to an A to D converter port of the processor.
7.5 Phase Detector
A phase detector is formed by T2, A1, and their associated components. This detector
indicates the state of any reactance associated with the antenna coupler as noted from
the generator. A line current sample is compared in phase with a voltage sample in a
double balanced mixer. The output of the phase detector A1 is shifted to a 0 to 5v
range, then fed to the processor’s A to D converter ports and used within the micro
controller.