After RF is applied to the tuner array, it then passes through the detector sys-
tem. The detector system consists of 6 capacitors in shunt on the input arm of
the network, arranged in binary increments, 8 inductors in the series arm,
arranged in binary increments, and 5 more capacitors in shunt on the output
arm, also arranged in binary increments. Relays are provided in conjunction
with each lumped constant and allow removal or entry as desired. A network
having 64 values on input shunt C, 32 values of output shunt C and up to 256
values of series L is possible with the manipulation of these 26 relays.
7
7..1
10
0 IIM
MP
PE
ED
DA
AN
NC
CE
E D
DE
ET
TE
EC
CT
TO
OR
R
RF transformers T1 and T2 drive the impedance bridge which is balanced at 50
ohms. T1 samples the line current and thus D8 outputs a negative DC level pro-
portional to line current. A tertiary winding on transformer T2 provides a
line voltage sample to D10 which provides a positive voltage proportional to
line voltage. R44 and R46 act as a summing network for the current and volt-
age 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 net-
work. The summing network output is applied to IC-15A which operates as a
ground referenced comparator. Low impedance is indicated by DS2.
7
7..1
11
1 V
VS
SW
WR
R D
DE
ET
TE
EC
CT
TO
OR
R
A directional coupler is made up of a current transformer T3 and a voltage
transformer T2, in conjunction with termination resistors R58 and R63. The
coupler is inserted in the 50 ohm transmission line between the input connec-
tor, J1, and the tuning network. The FORWARD power is measured across ter-
mination R63 and REFLECTED power is measured across termination R58. Diode
D11 generates a positive DC voltage proportional to FORWARD power and D12
generates a positive DC voltage proportional to REFLECTED power. The FOR-
WARD DC output is fed to a voltage divider consisting of R52, R54 and R62.
These voltages are input to the FORWARD detector and the inverting input of
the 4:1 and 2:1 VSWR comparators, IC-15B and IC-15C, respectively. The
REFLECTED DC output is input to the non-inverting input of both the 4:1 and 2:1
VSWR comparators. With the VSWR less than 2:1, both comparator outputs will
be low. If the voltage at the non-inverting input is higher than the voltage
51
© 1998 SGC Inc
SG-230 Manual
SGC Inc. SGC Building, 13737 S.E. 26th St. Bellevue, WA 98005 USA
P.O. Box 3526, 98009 Fax: 425-746-6384 Tel: 425- 746-6310 or 1-800-259 7331
E-mail: [email protected] Web site: http://www.sgcworld.com