Receiver Circuit Board Option - Crown FM30 User Manual

4.15 Receiver Circuit Board Option

This option allows the transmitter to be used as a translator. The receiver board receives
terrestrially fed RF signal and converts it to composite audio which is then fed into the ex-
citer board. Microprocessor controlled phase lock loop technology ensures the received fre-
quency will not drift, and multiple IF stages ensure high adjacent channel rejection. Refer to
illustrations 4–6, 6–16 and its schematic for the following discussion.
The square shaped metal can located on the left side of the receiver board is the tuner
module. The incoming RF signal enters through the BNC connector (top left corner) and is
tuned through the tuner module. Input attenuation is possible with the jumper labeled "LO"
"DX", on the top left corner of the receiver board. Very strong signals can be attenuated 20
dB automatically by placing the jumper on the left two pins ("LO" position). An additional 20
dB attenuation is also available with the jumpers in the top left corner of the board. The fre-
quencies are tuned by setting switches SW1 and SW2 (upper right corner). These two
switches are read upon power up (or by momentarily shorting J7) by the microprocessor
(U4). The microprocessor then tunes the tuner module to the selected frequency. The fre-
quency range is 87.9 Mhz at setting "00" to 107.9 Mhz at setting "64". Other custom ranges
are available.
Located in the lower left-hand corner of the Receiver Module is a 3.5mm headphone jack.
Demodulated Left and Right audio is present at this jack. A regular pair of 32 ohm stereo
headphones, such as the types used with portable audio devices, can be used to monitor
the audio on the receiver module.
Receiver
Module
Principles of Operation
Illustration 4–5 Receiver Module
4-15