Cobra Electronics Cobra 148 GTL - Manual (Page 6)

10
Section IV Operation (Continued)
4. SWR CAL CONTROL (outer dual concentric). In order for you to achieve
maximum radiated power and the longest range, it is important that your
antenna be in good condition, properly adjusted and matched to your trans-
ceiver. The Built-in SWR (standing wave ratio) meter lets you easily measure
your antenna condition. To operate this function, connect your antenna to
the transceiver antenna output connector. Select a channel near the middle
of the band such as 21 or the channel you plan to use most frequently. Turn
the power on and set the meter function switch to the CAL position. Press
and hold the microphone push-to-talk button and using the SWR CAL con-
trol, adjust the meter to read the CAL position indicated on the meter face.
Then, without releasing the microphone button, switch the meter function
switch to the SWR position and read the SWR indicated. The lower the fig-
ure, the better, with 1 being ideal. Generally speaking, readings up to 3 are
acceptable, but over 3 indicates that you are losing radiated power and
antenna adjustment may be advisable.
5. DYNAMIKE. Adjusts the microphone gain in the transmit and PA modes. This
controls the gain to the extent that full talk power is available several inches
away from the microphone. In the Public Address (PA) mode the control
functions as the volume control.
6. VOICE LOCK. Allows variation of the receiver operating frequencies above
and below the assigned frequency. Although this control is intended primari-
ly to tune in SSB signals, it may also be used to optimize AM signals as
described in the Operating Procedure paragraphs.
7. DIM/NOR/BRT SWITCH. Controls the brightness of the meter and LED
channel indicator for optimum intensity for day or night-time driving.
8. CHANNEL SELECTOR. This switch selects any one of the forty Citizens Band
channels desired. The selected channel appears on the LED readout directly
above the Channel Selector knob. Channel 9 has been reserved by the FCC
for emergency communications involving the immediate safety of life of indi-
viduals or immediate protection of property. Channel 9 may also be used to
render assistance to a motorist.
9. 0FF/ANL/NB + ANL SWITCH. In the ANL position only the automatic
noise limiter in the audio circuits is activated. When the switch is placed
in the ANL + NB position, the RF noise blanker also is activated. The
RF noise blanker is very effective for repetitive impulse noise such as
ignition interference.
Section IV Operation
CONTROLS AND INDICATORS
There are thirteen controls and three indicators on the front panel of your COBRA
148GTL.
A. CONTROL FUNCTIONS
1. OFF/ON/VOLUME (inner dual concentric). Turn clockwise to apply power to
the unit and to set the desired listening level. During normal CB operation,
the VOLUME control is used to adjust the output level obtained either at the
transceiver speaker or the external speaker, if used.
2. SQUELCH (outer dual concentric). This control is used to cut off or eliminate
receiver background noise in the absence of an incoming signal. For maxi-
mum receiver sensitivity it is desired that the control be adjusted only to the
point where the receiver background noise or ambient background noise is
eliminated. Turn fully counterclockwise then slowly clockwise until the receiv-
er noise disappears. Any signal to be received must now be slightly stronger
than the average received noise. Further clockwise rotation will increase the
threshold level which a signal must overcome in order to be heard. Only
strong signals will be heard at a maximum clockwise setting.
3. RF GAIN CONTROL (inner dual concentric). Used to reduce the gain of the
RF amplifier under strong signal conditions.
9