Cobra Electronics 150GTLDX - Manual (Page 8)

9 Nothing comes close to a Cobra ®
Controls
8 English
Installation and Connection
and Operation
Installation and Connection
•
If you are having difficulties in adjusting your antenna, check the following:
1. All doors must be closed when adjusting the antenna.
2. Make sure the antenna base is grounded.
3. Check your coaxial cable routing — it may be pinched where routed into the car.
4. Try a different location on your car — keeping in mind the radiation pattern you want.
5. Make sure the antenna is perfectly vertical.
6. Try a different location in your neighborhood. Stay away from large metal objects
(metal utility or light poles, fences, etc.) when adjusting.
NOTE
The radio will operate into a SWR of 2 to 1 indefinitely and sustain an
SWR of 20 to 1 for a maximum of 5 minutes at rated operating conditions.
- - External Speaker
The external speaker jack (EXT) on the rear panel is used for remote receiver monitoring.
The external speaker should have 8 ohms impedance and be able to handle at least
four watts. When the external speaker is plugged in, the internal speaker is disabled.
- - Public Address
To use the transceiver as a public address system, connect an external 8 ohm speaker
that is able to handle at least four watts to the PA jack on the rear panel. Direct the
speaker away from the microphone to prevent acoustic feedback. Physical separation
or isolation of the microphone and speaker is important when operating the PA at high
output levels.
Operation
•
There are 15 controls and 4 indicators on the front panel of your mobile radio.
These are shown in the illustration on page A2 which may be folded out for
reference when using this section.
Controls
•
- - Off / On / Volume
Turn clockwise to apply power to the unit and to set the desired listening level.
During normal operation, the volume control is used to adjust the output level
obtained either at the transceiver speaker or the external speaker, if used.
- - Squelch
This control is used to cut off or eliminate receiver background noise in the absence
of an incoming signal. For maximum 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 receiver
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
that a signal must overcome in order to be heard. Only strong signals will be heard
at the maximum clockwise setting.
- - Microphone Gain
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 for the PA speaker.
- - RF Gain
Used to reduce the gain of the RF amplifier when receiving very strong signals.
- - PA / AM / FM
Selects the mode of operation. In the AM and FM positions, the PA function is disabled
and the unit will transmit and receive on the internal speaker. In the PA mode, incoming
transmissions 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 four watts should be
used. This speaker must be plugged into the PA SPKR jack at the rear of the transceiver.
If the public 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 your
radio. With the PA speaker connected as outlined previously, be sure that there is physical
separation between the microphone and the speaker itself. If the speaker is located too
close to the microphone, acoustic feedback will result when the public address system
is operated 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
The microphone gain knob also controls the PA volume when in PA mode.
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