Tait Limited TEL0046 Betriebsanleitung
T836/837 Initial Tuning & Adjustment
C3.11
Copyright TEL
23/07/99
3.9
Audio Processor & CTCSS
3.9.1
Two Point Modulation
The T836 and T837 utilise two point modulation to obtain a wide audio bandwidth
independent of the synthesiser loop filter response. This is achieved by simultaneously
frequency modulating the VCO and phase modulating the synthesiser reference fre-
quency. The relative signal levels fed to the two modulators are quite critical and cause
interaction when setting up.
independent of the synthesiser loop filter response. This is achieved by simultaneously
frequency modulating the VCO and phase modulating the synthesiser reference fre-
quency. The relative signal levels fed to the two modulators are quite critical and cause
interaction when setting up.
Both modulating signals require readjustment when the exciter is shifted in frequency
greater than the switching range (i.e.
greater than the switching range (i.e.
∆
F>±4MHz).
Note 1:
In this and following sections deviation settings are given first for wide
bandwidth sets, followed by settings in brackets for mid bandwidth sets ( )
and narrow bandwidth sets [ ].
bandwidth sets, followed by settings in brackets for mid bandwidth sets ( )
and narrow bandwidth sets [ ].
Note 2:
The reference modulation and limiter adjustments are controlled by 256-
step electronic potentiometers (EPOTs), which are adjusted via the “Refer-
ence Modulation” and “Deviation” settings in PGM800Win. This allows the
two point modulation and deviation settings to be adjusted for each chan-
nel.
step electronic potentiometers (EPOTs), which are adjusted via the “Refer-
ence Modulation” and “Deviation” settings in PGM800Win. This allows the
two point modulation and deviation settings to be adjusted for each chan-
nel.
Note 3:
To optimise the modulation response across the switching range, repeat
steps 1-4 below for each channel that will be used (usually needed only for
data applications). In applications where the modulation response is less
critical (e.g. voice use only), carry out steps 1-4 below on the middle channel
and use the “EPOT Fill” option
steps 1-4 below for each channel that will be used (usually needed only for
data applications). In applications where the modulation response is less
critical (e.g. voice use only), carry out steps 1-4 below on the middle channel
and use the “EPOT Fill” option
1
in PGM800Win to copy the value to the
other channels.
3.9.2
Modulator Adjustment
1.
Inject an audio signal of 600Hz 1.5V rms (+5dBm) into the CTCSS input (D-range
1 (PL100) pin 8).
1 (PL100) pin 8).
Key the transmitter by earthing the Tx-Key line.
2.
Adjust the output from the audio generator to obtain ±3kHz (±2.4kHz) [±1.5kHz]
deviation at 600Hz.
deviation at 600Hz.
3.
Change the input frequency to 120Hz and, using PGM800Win, adjust the value of
the “Reference Modulation” EPOT setting for the current channel to obtain ±3kHz
(±2.4kHz) [±1.5kHz] deviation (you can use either the mouse or up and down
arrow keys).
the “Reference Modulation” EPOT setting for the current channel to obtain ±3kHz
(±2.4kHz) [±1.5kHz] deviation (you can use either the mouse or up and down
arrow keys).
4.
Change the input frequency back to 600Hz.
Repeat steps 2 and 3 above until the deviations achieved at the two input frequen-
cies are within 0.2dB of each other. You will need to do this at least four times.
cies are within 0.2dB of each other. You will need to do this at least four times.
1. Use the “EDIT FILL” button on the tool bar or go to “Edit”, “Fill”, “Epot Settings” on
the menu bar.