Como definir a SWR e sintonizar a antena do rádio CB?

Always follow the operating instructions for the radio, antenna, and SWR meter.

While the procedures are basically more or less identical, they may vary depending on the type of equipment.

Caution: Never transmit without an antenna or with an antenna that is not properly tuned.

A poor SWR value can damage the radio!

Installation

1. Install the antenna at the transmitting location.

Make sure that the antenna is installed as it will be used later.

2. Connect the antenna cable to the SWR meter.

(The connection should be marked with [ANT] or [Antenna])

3. Connect the SWR meter to the radio using a short connection cable (max. 50 cm).

(The connection should be marked with [TX].)

Important: additional devices, such as antenna switches, must be connected between the SWR meter and the antenna.

The complete antenna system including switches etc. must be measured.

4. Connect the radio to the power source, turn on the radio, modulation [FM]

SWR Measurement (CB Radio)

1. Set the radio to channel 20.
2. Set the switch of the SWR meter to the [FWD] position (level measurement).
3. Press and hold the [PTT] button of the microphone
4. Turn the [CAL] control on the SWR meter until the meter needle reaches the [SET] or [∞] position.
5. Release the [PTT] button.
6. Set the switch of the SWR meter to the [REF] position (reading the SWR value).
7. Press the [PTT] button, the meter will now show the SWR value.

These steps must be repeated after each change to the antenna system.

SWR Values

• Values above 1:3 will damage the transmitter stage of the radio!

Either the antenna is incorrectly installed or the cable has a short circuit.

Do not transmit!

• An SWR value between 1:1 and 1:1.5 is acceptable, no further adjustment to the antenna is needed.
• Values above 1:1.5 up to 1:2.5 – it is recommended to adjust the antenna.
• Measurement range: Measure the middle of the used frequencies (channel 20) as well as the lowest and highest frequency.

For 40 channels according to EU standard, this is channel 01 (low) and channel 40 (high).

The SWR value must be below 1:3 on all channels used

Adjustment of the antenna for the frequency range 26.965 MHz to 27.405 MHz (40 channels / EU standard).

The antenna must be adjusted according to the operating instructions.

Basically:

In most cases, cutting to shorten is not necessary. In any case, follow the operating instructions for your antenna.

A low SWR value on channel 01 / High SWR value on channel 40 – The antenna is too long (must be shortened)

A high SWR value on channel 01 / Low SWR value on channel 40 – The antenna is too short (must be lengthened)

Most antennas have an adjustment screw so that the transmitting element can be pulled out or pushed in.