Installation
C-19
If the CW message is still too loud with the pot turned nearly all the way down,
you may be attempting to drive the microphone input of the transmitter instead
of a later stage.
If you cannot drive a later stage, check the Transmitter Audio Output on page
C-7 for hints for decreasing the transmitter drive level.
Testing The Controller-To-Repeater Receiver Interface
Generate an RF signal on the repeater’s input frequency. The controller should
key the repeater transmitter. When the signal disappears, a short courtesy
beep should be heard. The transmitter should stay keyed for a few more
seconds, then it should unkey.
If this does not happen:
• Check the wiring between the repeater receiver’s COR driver and the
controller’s Receiver #1 COR Input.
• Check the voltage on the COR line to see if it swings above and below the
required threshold. (Check the voltage with the controller and receiver
connected, not just the open-circuit COR output from the receiver).
If the repeater is acting upside down (unkeying when a signal exists but keying
afterwards), reverse the Receiver #1 COR DIP Switch.
The default condition of the controller causes a 0.5-second delay between the
loss of carrier and the courtesy beep. The transmitter will stay keyed for an
additional 3.0 second dropout delay. These characteristics may all be changed
later, so do not be concerned if this is not the way you wish the repeater to act.
• Generate a modulated RF signal on the repeater’s input frequency (a
service monitor is quite helpful).
• Check the audio level as instructed in the Repeater Receiver Audio section
on page C-6.
• Check the transmitter for proper deviation, and
• Adjust the Transmitter #1 Audio Output pot as necessary.
Testing The DTMF Decoder
Your controller uses an 8800-Type DTMF Transceiver IC. This crystal-
controlled device encodes and decodes all 16 DTMF digits. It has an extremely
wide dynamic range (30 dB), and can detect digits that have as much as -6 dB
to +6 dB of twist.
Twist refers to the difference in amplitude between the two individual tones that
are summed to make up a DTMF digit. The more twist a system gives to DTMF
digits, the more difficult it is to detect the digits. In repeater systems, twist can
be caused by the user’s transmitter.
The audio fed into the transmitter is pre-emphasized before it is applied to the
limiter circuit. Pre-emphasis causes high frequency tones to have more
amplitude than low frequency tones, so the high frequency tone of a DTMF
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