ZETRON 748, Техническое руководство

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Installation
025-9368H 13
Using a computer or terminal:
Select “CTCSS/DCS encode gain and pre-emphasis adjust” by typing “6” followed by
ENTER
. This
will cause the transmitter to key up with the CTCSS tone 67.0 Hz encoded. Each time a key is
pressed, it will advance to the next tone in the list (67.0, 136.5, 250.3 D023).
Using a DTMF telephone:
Using the phone, enter the DTMF programming mode as explained earlier. Enter the transmitter
setup tests by entering the function code “112#”. This will cause the transmitter to key up with the
CTCSS tone 67.0 Hz encoded. Each time any DTMF digit is pressed other than “#” or “*”, the
Model 748 will cycle to the next tone in the list (67.0, 136.5, 250.3 D023).
Adjusting CTCSS/DCS level:
Press any key once to get to 136.5 Hz. Adjust R63 (SUBOUT) for 750 Hz deviation on the channel.
Next, check the lower and upper tones for the proper deviation by cycling through the tones. Verify
a flat response (CTCSS at 750Hz, DCS at 1Kz). JP27 can be used to increase or decrease the output
if needed. JP27 in position A increases the output and decreases it in position B. JP26 can be used to
set the tones for a flat response. JP26 in position B de-emphasizes the sub-audible tones. JP26 in
position A sends the sub-audible out flat.
Using a computer or terminal:
Press ENTER to leave the test.
Using a DTMF telephone:
Press “#” to leave the test mode.
4. DISCRIMINATOR INPUT: Adjust the receiver audio level by supplying a full quieting signal
to the receiver. This signal should have a 1kHz tone at 60% of maximum deviation (3kHz
typical). Adjust R59 for 375mVrms (1.0 Volt P-P) at TP4 measured with an oscilloscope. Verify
DTMF decoding with a handheld or service monitor with DTMF encoding capability. Note
digits 1, 5, 9 and D cover all 8 tones. The DTMF LED should light with each digit.
5. REPEAT AUDIO ADJUSTMENT: If the Model 748 is used on a repeater or full-duplex base
station, R59 can be fine tuned using the Repeat Audio test.
Using a computer or terminal:
Select “Repeat audio adjust” by typing “7” followed by
ENTER
.
Using a DTMF telephone:
Enter the correct function code 113#.
Adjusting Repeat audio:
The Model 748 now keys up and remains keyed for the duration of the test. The repeat audio
path is gated with COR detection. R59 should now be used to adjust the repeat audio for
unity gain through the Model 748. DO NOT adjust R60 during this procedure. It was already
set to the proper level in step 2.
First, generate a 1 kHz tone at 60% of maximum deviation (typically 3kHz) on the same
frequency as the receiver connected to the Model 748. This can be done with a service
monitor or a handheld using Touch-Tone instead of a 1 kHz tone. If you are using a