3. SWR Measurement
Do not turn on the transmitter, while the antenna and test
meter are disconnected.
To use this SWR meter, it must be connected to the antenna feet
line. To do this, a short coaxial cable, not longer than two feet, is
required.
With the transmitter off, disconnect the antenna coax cable from
the transmitter and connect the coax cable to the ANT jack (2) of
the SWR meter. Connect the short coax cable between the transmitter and the TX-jack (1) of the SWR meter.
The antenna coax cable should not be longer than two feet. The
use of a longer cable distorts the measurement.
> Select the proper power range with
the power selector (6) [10 W/100 W].
CB radios, normally, have a max. tx
power of 4 Watts. The tx power is
indicated on the left display (5).
> Set the sliding switch (7) [FWD/REF]
to the FWD position.
> With the transmitter turned on, set
the calibration knob (3) [CAL] to full
scale deflection, i.e. [SET].
> Set the sliding switch (7) to position [REF] and read the right
display on the upper scale (5). This is the standing wave ratio.
> The relative output power is displayed on the left meter (5).
If the SWR is above 2:1 the antenna may need tuning or there
may be a problem in the antenna system (connectors).
Several antennas provide a means for tuning by either a slide
adjustment or a control at the base. For sliding antennas, sliding
¼'' each time and repeating the SWR measurement steps after
each adjustment. First, move the antenna inwards and observe for
an improvement in the SWR, than outwards if no improvement is
noticed. Select a center channel at the transmitter for the measurements.
With 40 channel CB radios, channel 19 FM should be used for
adjustment. Then, check channel 1 and channel 40 for comparison.
With 80 channel CB radios, use channel 1 FM for adjustment and
channel 41 (26,565 MHz) and channel 40 (27,405 MHz) for comparison.
SWR reflected power SWR reflected power
1,0 :1 0 % 2,0 : 1 10 %
1,22:1 1 % 2,33: 1 16 %
1,5 :1 4 % 3,0 : 1 25 %
1,85:1 9 % 4,0 : 1 36 %