Section IV Operation (Continued)
10.PA/CB SWITCH. Selects the mode of operation. In the CB position, the PA func- tion is disabled and the unit will transmit and receive on the speaker that is con- nected. In the PA mode, incoming CB transmission will be heard through the PA speaker. This allows you to monitor messages while outside of your vehicle.
To use the PA feature, a speaker having a voice coil impedance of 8 ohms and a power handling capability of at least three watts should be used. This speaker must be plugged into the PA SPKR jack at the rear of the transceiver. If the pub- lic address feature is to be used primarily for outdoor applications, the use of a weatherproof horn type public address speaker is recommended. The durability of this type speaker plus the inherent efficiency of such a speaker will provide more than adequate results when combined with the high audio output level available from the COBRA 148GTL. With the PA speaker connected as out- lined previously, be sure that there is physical separation between the micro- phone and the speaker itself. If the speaker is located too close to the micro- phone, acoustic feedback will result when the public address system is operat- ed at high volume. A directional type outdoor speaker reduces the amount of isolation required. Some experimentation will determine the minimum amount of isolation required for a given sound level from the public address system.
NOTE
PA volume is controlled by adjusting the DYNAMIKE knob to the desired volume.
11.
When in the “CAL” position, the SWR meter can be calibrated by adjusting the “SWR” control to the “CAL” mark on the meter face.
When in “SWR” position, the standing wave ratio is measured.
12.MODE (LSB/AM/USB) SWITCH. This switch is used to select AM, LSB or USB mode of operation. Unless the station with which communication is desired is equipped with SSB, the AM mode is normally used. The mode selector switch changes the mode of operation of both transmitter and receiver simultaneously. Turn to “Receiving SSB signals” for a further explanation of single sideband.
13.TONE
11
Section IV Operation (Continued)
B. INDICATOR FUNCTIONS
1.
2.RF METER. Swings proportionally to the RF output power.
3.SWR METER. Swings proportionally to the ratio of standing wave voltage and RF output. Used to properly adjusts the length of the antenna, and to monitor the qual- ity of the coaxial cable and all RF electrical connections. If there is any degradation whatsoever in any of the above, due to humidity, salt, spray, vibration or corrosion, the SWR meter reading will rise, thereby indicating that a problem exists.
To calibrate, switch to the “CAL” position, transmit in AM Mode by pressing the (PTT) mic switch, and adjust the SWR control to the “CAL” mark on the meter then switch to “SWR” position for the SWR measurement (Note: CB must be in AM mode).
4.CHANNEL INDICATOR. Numbered LED indicates the selected channel you wish to operate on.
5.RECEIVE/TRANSMIT INDICATOR. The receiver/transmit LED indicator is located next to the channel indicator. When in receive, the LED will be green. When in transmit the LED will be red.
6.
OPERATING PROCEDURE TO RECEIVE
1.Be sure that the power source, microphone and antenna are connected to the proper connectors before going to the next step.
2.Set
3.Set the VOLUME for a comfortable listening level.
4.Set MODE switch to the desired mode.
5.Set the RF gain control fully clockwise for maximum RF gain.
6.Listen to the background noise from the speaker. Turn the SQUELCH control slowly clockwise until the noise JUST disappears (no signal should be pre- sent). Leave the control at this setting. The SQUELCH is now properly adjust- ed. The receiver will remain quiet until a signal is actually received. Do not advance the control too far, or some of the weaker signals will not be heard.
7.Set the CHANNEL selector switch to the desired channel.
8.Adjust the VOICE LOCK control to clarify the SSB signals or to optimize
AM signals. | 12 |
