Harmonic Filter; Antenna Switch - Motorola APX 7000 Detailed Service Manual
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Also See for APX 7000:
- Basic service manual (292 pages) ,
- User manual (213 pages) ,
- Quick reference card (98 pages)
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Theory of Operation: Transceiver Board
3.1.3.4 Harmonic Filter
The harmonic filter is a high-power, low-loss, low-pass filter. Its purpose is to suppress transmitter
harmonics. The filter also improves receiver out-of-band rejection. Shield SH13 must be in place to
achieve the required stop band rejection.
VHF: The harmonic filter uses discrete components. The pass band is up to 190 MHz, and the stop
band is above 260 MHz.
UHF1: The harmonic filter apply discrete components as the circuit line up. The pass band is up to
520 MHz while the stop band is above 1200 MHz.
UHF2: The harmonic filter uses both discrete components and transmission lines. The pass band is
up to 640 MHz, and the stop band is above 840 MHz.
700–800 MHz: The harmonic filter uses both discrete components and transmission lines. The pass
band is up to 870 MHz, and the stop band is above 1500 MHz.
3.1.3.5 Antenna Switch
NOTE: Refer to
schematics that will aid in the following discussion.
The antenna switch consists of a single pole triple-throw IC designated U1102. The IC is connected
to the output of the two harmonic filters and it is connected to the receiver. The output of the switch is
connected to the directional coupled via the inductor L1108. Control lines V1_V2 and V3 control the
routing of the signal paths. During Rx operation, V3 is set high and V1_V2 is low.
Tx Operation:
• VHF / 700–800 MHz:
VHF: V3 is set Low and V1_V2 is set High
7/800: V3 and V1_V2 are set High
• UHF1 / 700–800 MHz:
UHF1: V3 is set Low and V1_V2 is set High
7/800: V3 and V1_V2 are set High
• UHF1 / VHF:
UHF1: V3 and V1_V2 are set High
VHF: V3 is set Low and V1_V2 is set High
• UHF1 / UHF2:
UHF1: V3 is set Low and V1_V2 are set High
UHF2: V3 is High and V1_V2 are set High
• UHF2 / 700–800 MHz:
UHF2: V3 is set Low and V1_V2 is set High
7/800: V3 and V1_V2 are set High
• UHF2 / VHF:
UHF2: V3 and V1_V2 are set High
VHF: V3 is set Low and V1_V2 is set High
Table 8-1, "Transceiver Schematics and Board Overlays," on page 8-1
3-19
for a listing of
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Troubleshooting
