Variable Split Band Inverter
9
MX214/224
5.
Application
The MX214 represents both the MX214 and the MX224 throughout this section.
Recommended external components are shown in Figure 2 and Figure 3. In ‘Scramble’ mode, split point
frequencies are selected and set in accordance with the ROM address code present at the inputs A0-A4. See
Table 4. In ‘Clear’ mode, both upper and Lowerband filter limits are used (see Figure 6 and Figure 7), the
carrier frequencies are turned off, and the balanced modulators are bypassed internally. The Lowband audio
is removed from the output signal prior to summing.
ROM
Address
A4-A0
Split Point
Hz
Low Band
Carrier, Hz
High Band
Carrier, Hz
ROM
Address
A4-A0
Split Point
Hz
Low Band
Carrier, Hz
High Band
Carrier, Hz
f
f
f
f
C1
C2
C1
C2
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
2800
2625
2470
2333
2210
2100
2000
1909
1826
1750
1680
1555
1448
1354
1272
1200
3105
2923
2777
2631
2512
2403
2304
2212
2127
2049
1984
1858
1748
1655
1572
1501
6172
6024
5813
5681
5555
5494
5376
5263
5208
5102
5050
4950
4807
4716
4629
4587
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
1135
1050
976
913
857
792
736
688
636
591
552
512
471
428
388
350
1436
1351
1278
1213
1157
1094
1037
988
4504
4424
4347
4310
4273
4166
4132
4065
4032
3968
3937
3906
3846
3816
3787
3731
936
891
853
813
772
728
688
650
Table 4: ROM Address Programming
The MUTE function disables the MX214/224’s audio outputs to allow periodic transmission of synchronization
data. A logic ‘0’ at this input isolates the device while leaving the audio input and output ins at bias level (See
Table 2). When the MX21/224 is in Powersave mode, audio signals may be hardwired around the device
since the input and output pins are open circuit. See Table 2.
5.1
Audio Quality
Figure 4 shows the recommended basic audio system layout using pre- and de-emphasis circuitry to maintain
good recovered speech quality. The Transmit mode, Do Not pre-emphasize the audio output of the MX214.
In the Receive mode, de-emphasis should be used after the MX214.
Amplitude
Control
Amplitude
Control
Pre-emphasis
MX214
Tx
Rx
MX214
De-emphasis
Flat Amplitude
Channel
300-3400Hz
Frequency
Inverter
Frequency
Inverter
(Optional)
(Optional)
Figure 4: Recommended Basic Communication Audio System Layout
Figure 5 shows the recommended basic audio system layout if it is necessary to install the MX214 within a
radio having pre- and de-emphasis circuitry as a standard. This is where post-emphasis access is not
possible in the transmitter.
ꢀ1998 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480112.002
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