CB/High-Frequency Ham Power SWR Meter
(210-0534)                 Operation                  Faxback Doc. # 47559

MEASURING SWR

Measuring SWR shows you how much of your radio's transmit power is
reflected from the antenna back into the antenna cable, generating heat
and wasting power.  With this information, you can adjust the length of
your antenna or antenna cable so your antenna and radio combination can
produce the maximum power they are capable of producing.

For more information about measuring SWR, see the ARRL Handbook, available
at your local library.

CONNECTING THE METER

To connect this meter to your CB or amateur radio and your antenna, you
need RG-58U coaxial cable (not supplied) with a PL-259 connector on both
ends (such as RadioShack Cat. No. 278-968).  The cable must reach from the
back of the meter to your radio's antenna jack.

Follow these steps to connect the meter to your radio and antenna.

1.  Turn off your radio.  Then disconnect the antenna from the radio and
    plug it into ANTENNA on the back of the meter.

2.  Plug the coaxial cable into the radio's antenna jack and into
    TRANSMITTER on the back of the meter.

CALIBRATING THE METER/MEASURING SWR

1.  Turn on your radio.  Then set FUNCTION on the front of the meter to
    CAL.

2.  Select a channel or frequency on your transmitter and hold down its
    transmit key.  Do not speak into the microphone.

    Notes:  An SWR reading will be different for different frequencies
            (channels).  If you transmit on one channel more often than
            any other, select that channel.  If you transmit on several
            channels, choose a frequency in the middle of the range of
            channels you use.  (For example, if you transmit on all 40 CB
            channels, choose Channel 20, because it is midway between
            Channel 1 and Channel 40.)

            If you use a CB that has sideband modes (SSB), do not select
            any of these modes.  (Use only AM for SWR measurements.)

            If you have an amateur radio, select the continuous wave (CW)
            or tuning mode to check the SWR.

3.  While you hold down the transmit key, rotate CALIBRATION on the front
    of the meter until the needle points to CAL.

4.  Release the transmit key, then set FUNCTION to SWR.

5.  Press the transmit key again, then find the SWR by reading the
    appropriate scale on the meter.

      If your transmitter's power is less than 20 watts, read the lower
      scale (marked with an L on its right side).

      If your transmitter's power is more than 20 watts, read the upper
      scale (marked with an H on its right side).

INTERPRETING SWR READINGS

An ideal SWR reading is 1.0, but this reading is usually possible only
under laboratory conditions or with a dummy load.  Actual antenna
installations have higher readings.  The information below will help you
interpret the readings you get.

SWR          Efficiency    Interpretation

1.0 to 1.5   Excellent     The antenna cable and the antenna length match
                           the transmitter's output requirements almost
                           perfectly.

1.5 to 2.0   Very good     The antenna, the cable, and transmitter operate
                           very efficiently.

2.0 to 3.0   Acceptable    The antenna, the cable, and the transmitter
                           operate with some loss.  If possible, adjust
                           your antenna or antenna mounting system to
                           improve.

Above 3.0    Inefficient   Adjust your antenna or antenna mounting system
                           to improve efficiency.

When you measure SWR, use this chart to determine the percentage of power
that is wasted through reflection of the signal back to the radio.

SWR               1.0     1.1     1.2     1.5     2.0     2.5     3.0

Ref. Power (%)    0       0.22    0.8     4.0    11.1     18.4   25.0

For example, an SWR reading of 1.5 also means that 4% or your signal power
is lost.  However, 96% of the radio's power is more than enough for almost
all applications.

IMPROVING SWR

There are several ways to improve the SWR of your radio/antenna
combination.  Try these first.

  Be sure you are using the type of cable recommended for your equipment.
  If the manufacturer recommends a 50-Ohm cable, do not substitute another
  type that has a different impedance.

  Confirm that you mounted your antenna according to the manufacturer's
  instructions.  The angle and the base arrangement can affect the SWR
  reading.

  Adjust the length of your antenna according to the instructions provided
  by the manufacturer.  A change of as little as 1/8 inch can make a
  measurable difference.

  See your radio and antenna's owner's manuals.

MEASURING POWER

You can use your meter to show how much power your radio is transmitting.
You can use this information with the SWR reading (see "Measuring SWR"
above) to determine the efficiency of your antenna and radio combination,
or to make sure that your antenna and radio combination are operating
within legal limits.

For more information about measuring power, see the ARRL Handbook,
available at your local library.

IMPORTANT:  To accurately measure power using SSB, you must connect a low
            frequency oscillator (not supplied) capable of generating a
            1000 - 1500 Hz tone signal to the transmitter.  This procedure
            should be performed by a qualified technician.

Follow these steps to measure your transmitter's power output.

1.  Set FUNCTION to POWER.

2.  Set RANGE on the front of the meter to the correct range for your
    transmitter.

      If your transmitter's power is 20 watts or less, set RANGE to 20W.

      If your transmitter's power is more than 20 watts but 200 watts or
      less, set RANGE to 200W.

      If your transmitter's power is more than 200 watts, or you do not
      know the transmitter's power, set RANGE to 2000W.

3.  Set MODE on the front of the meter to the correct setting for your
    transmitter.

      If your transmitter uses SSB or CW, set MODE to PEP to measure peak
      envelope power.

      If your transmitter uses another type of output, set MODE to AVG to
      measure average power.

4.  If your transmitter does not use SSB, select a channel or frequency on
    your transmitter and hold down its transmit key. Do not speak into the
    microphone.

    If your transmitter uses SSB, input a 1000 - 1500 Hz tone signal from
    the low-frequency oscillator you connected to the transmitter.  Then,
    select a channel or frequency on your transmitter and hold down its
    transmit key.  Do not speak into the microphone.

5.  Read the power level by noting the needle's position on the correct
    POWER scale.

      If you set RANGE to 20W in Step 2, read the lower scale (marked with
      an L on its right side).

      If you set RANGE to 200W or 2000W in Step 2, read the upper scale
      (marked with an H on its right side).

Note:  If the power level is extremely low within the range you selected,
       set RANGE to a lower setting and repeat Steps 4 and 5.

(BR/tc 5/14/98)