Micronta Field Strength and SWR Tester
(210-0525)                 Operation                  Faxback Doc. # 48544

TYPICAL ANTENNA RADIATION PATTERN

The majority of signal will be transmitted in the direction of the
greatest amount of perceived "ground plane".  Example, a CB antenna
mounted on the rear of a vehicle will transmit the majority of it's signal
toward the front of the vehicle.

If the antenna is mounted on the center line of the vehicle, the signal
will have a uniform side pattern.

NOTE:  Antennas may not radiate equally in all directions, especially a CB
       antenna mounted on a car.

CONNECTING AND USING THE SWR METER

The SWR function uses the top scale on the Meter.  It measures the amount
of mismatch between the CB unit and the antenna system.  To use the SWR
meter:

1.  Disconnect the Antenna Cable from your CB unit.

2.  Connect the Antenna Cable to the ANT connector on the FS/SWR TESTER.

3.  Connect one end of a short 52 Ohm (RG-8U or RG-58/U) coaxial cable to
    the Antenna jack on your transceiver and the other end to the TRANS
    connector on the FS/SWR TESTER.

NOTE:  RadioShack has 2' (0.6 m) and 5' (1.5 m) coaxial cables for this
       purpose.

4.  Set the FWD-REF switch to the FWD position.

5.  Remove the short antenna wire from the top of the FS/SWR TESTER.

6.  Press the Push-to-talk switch on your CB unit (don't talk into the
    mike).  Adjust the CAL control for a full-scale reading on the Meter
    (to the SET mark).

7.  Set the FWD-REF switch to REF and press the PUSH-to-talk switch again.
    The reading on the SWR scale is the ratio of the impedance mismatch
    between the coaxial cable and the antenna.

CONNECTION FOR SWR MEASUREMENT

A perfect SWR reading of 1 to 1 is indicated by no meter needle movement
(a reading of 1 on the SWR meter scale).

A reading of 1.2 to 1.5 (1.2 to 1 up to 1.5 to 1) is considered OK.  A
reading greater than 1.5 means you are starting to lose a significant
amount of transmitting power due to impedance mismatch.  You can relate
the SWR reading to the amount of power being lost (reflected back from the
Antenna).  See the chart below:

SWR READING                                                     POWER LOST

1.5 to 1 ............................................................. 4 %

2.0 to 1 ............................................................ 11 %

2.5 to 1 ............................................................. 19%

3.0 to 1 ............................................................. 25%

The power that is lost is reflected back from the Antenna.  If the SWR is
high enough for a significant amount of time, it will cause overheating
and may lead to CB unit failure.

NOTE:  If you operate the CB unit without an antenna or load, all of the
       power must be dissipated in the "Final" stage of the CB transmitter
       (no power being transferred to a load).  This condition corresponds
       to an infinite SWR.  Many CB units will quickly overheat, resulting
       in destruction of the unit.  Thus, never operate your CB unit
       unless you have an antenna or suitable load connected.

The FS/SWR TESTER is designed to provide a minimum amount of loss when
inserted between the CB unit and antenna.  You can leave it connected all
of the time to conveniently check any change in SWR.

THE FIELD STRENGTH METER

The FS METER measures the relative strength of the signal radiated by an
antenna.

USING THE FIELD STRENGTH METER:

1.  Set the FWD-REF switch to FWD.

2.  Install the small antenna supplied with the FS/SWR TESTER into the
    jack marked FS ANT on the front panel.

    NOTE:  A longer piece of wire may be connected to the jack for greater
           sensitivity.

3.  Check and make sure the CB unit is connected directly to its antenna
    and not through the FS/SWR TESTER.

4.  Press the Push-to-talk switch on the CB unit (usually a button on the
    microphone) and adjust the CAL knob for a reading from 2 to 4 on the
    Meter's FS scale.

Sometimes you can increase the radiated signal by changing the type of
coaxial cable, or you can change or adjust the antenna.  If you leave the
FS/SWR TESTER in one location and don't change the CAL control setting,
you should be able to see any improvement in the strength of the radiated
signal by an increase of the Field Strength reading.

Another use for the FS METER is to plot the radiation pattern of your
antenna.  Set the FS reading to a level between 2 and 4 on the Meter's FS
scale.  Then move the FS/SWR TESTER around the antenna in a circular
pattern.  Move closer or further away form the antenna to keep the same FS
reading.  Thus you can map the radiation pattern.

(BR/eb 6/30/98)

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