Ctcss; Decoder Operation; Opening Sinad; High Pass Filter - Tait T880 II Series Adjustment Manual

M880-00
3.4.6

CTCSS

3.4.6.1

Decoder Operation

Program a CTCSS tone on the default channel using PGM800Win.
Set the RF signal generator output to -70dBm.
Modulate the generator with both:
• a 1kHz tone at ±3kHz deviation [±1.5kHz]
• and a CTCSS tone at the programmed frequency at ±500Hz deviation [±300Hz].
Check that the receiver gate opens and the front panel "Gate" LED is on.
3.4.6.2

Opening Sinad

Adjust RV230 (front panel gating sensitivity) fully clockwise.
Reduce the RF signal level to -110dBm.
Observe the sinad meter and reduce the RF level until the receiver mute closes.
Slowly increase the signal level until the receiver mute just opens and stays open.
With PL240 pins 1 & 2 linked (high pass filter bypassed), check that the sinad is
less than 6dB.
Reset the signal generator for the required opening sinad, adjust RV230 fully anti-
clockwise, then clockwise until the mute just opens.
3.4.6.3

High Pass Filter

Set the audio processor links as follows:
Plug
PL210
PL230
PL240
Reset the RF signal generator output to -70dBm and note the line level (measure-
ment A).
Reduce the 1kHz generator to zero output and measure the line level again (meas-
urement B).
Check that measurement B is at least 30dB below measurement A.
Copyright TEL
T885 Initial Tuning & Adjustment
Link
1 - 2 de-emphasised response
2 - 3 audio from internal CTCSS speech filter
4 - 5 audio input via PL230 or I/O pad
Function
B3.7
10/07/00