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LPB Communications, Inc.
ATU-20 Antenna Tuning Unit
6.
Determine the SWR. Set S2 in forward (FWD)
Adjust R8 for full scale (1.0)
Set S2 in reflect (REF), note reading and calculate.
1 .0
+
reading
= SWR
1.0- reading
For example, if reading is 0.2:
1.0+ 0.2
1.0-0.2 =1 .5, so the SWR is l .5:1
NOTE: The meter reading in REF must be approx.. 0.3 or lower (2: 1 or better SWR) for proper transmitter
operation.
7.
Set Sl to Operate
8.
Reduce transmitter RF power to the minimum necessary for desired area coverage.
Broadcasting
The ATU-20 Antenna Tuning Unit is specifically designed to compensate for the inefficiencies of antennas, and to
provide an acceptable transmitter to antenna match. Specifically, the ATU functions to:
1.
Isolate the transmitter from voltage through the use of high pass capacitors and fuses.
2.
Compensate for antenna impedance mismatch through the use of multi-tap toroidal transformers.
3.
Compensate for antenna reactance through the use of a decade system of capacitor combinations.
An internal VSWR metering system indicates when the proper combination of corrective settings has been selected
for optimum signal transfer.