Kth - sdr - kit

6/13/2010 KTH - SDR - KIT Page 11
________________________________________________________________________________
2.3 Assembling and testing the Synthesizer module.
See the schematic on figure 2.3-1. The frequency generation is accomplished by the Si570 clock generator
made by Silicon Labs and covers 3.5 MHz to 440 MHz. Controlling of the complete receiver is done by a
Microchip PIC 18F2550. This microcontroller generates I2C data for most of the modules and communicates
via USB with the host computer. Most of the I/O ports are available on block headers or card edge
connectors. For initial PIC programming, an ICSP connector is available on the board. Firmware upgrades
are carried out through the USB port after setting the PIC in ‘Bootload’ mode. There are two LED’s on the
board: one as a power indicator and the other one for indicating that the PIC is in Bootload mode.
The 5 Volt power supply can be obtained (set by jumper J1) from the USB port (only for testing the USB
connection) or from voltage regulator VR1 for normal use. Because the Si570 needs only 3.3 Volt, there is
also a 3.3 Volt regulator on the board. To adjust the 5 Volt I2C levels from the PIC to the 3.3 Volt level of
the Si570, a bidirectional voltage translator interface IC2 is used.
The balanced RF output of the Si570 is adjusted by TR1 to the 50 ohm impedance of the MAV-11 to get for
the I/Q demodulator LT5517 a stable and strong signal.
Frequency tuning of the Si570 can be done via USB commands or the 24 pulse per revolution encoder as
well.
Pull-up resistors are necessary for the function push buttons connected to the RA-ports. You can place these
resistors near the buttons on the LCD board, or you can use a resistor array (R17 – not in kit) on the
Synthesizer board.
In figure 2.3-2 en 2.3-3 you will see the location of the components.
Install the components as follows:
Solder first R3 before the DIL28 IC-socket will be placed. Next, on the backside, solder the 3.3 Volt
regulator VR2 en the components: D2, C19, C17, C14, C15, L2, C10, C11 and C9. VR2 takes care of the 3.3
Volt supply of the Si570 and GTL2002. Check if the code stamps on VR2 is N05B.
Solder the 5 Volt regulator VR1 on the board and next the components C5, C6 and C7. VR1 takes care of the
5.0 Volt supply of the PIC and also the LCD board. Check if the code stamps on VR1 is N06B.
Now the regulators and accompanying parts are in place, you can put the module in the motherboard
connector and connect the 12 Volt DC to the motherboard.
Caution: When you place a module in the motherboard connector, be sure the
module is in the corresponding connector and in the right way. Be sure the
module connector pin 1 and 2 and the Motherboard connector pin 1 and 2 are
in the same position! If you place a module in the wrong way, it can be
irreparable damaged!
Tip: Use a 12 Volt external power supply with a 1 Amp (max) fuse and or use a
series resistor of about 10 ohm 5 Watt in the DC line for sure.
Check the 5 Volt and 3.3 Volt on the test points on the Synthesizer board.
If all the supply voltages are OK, then you can continue with the rest of the components.
Note: CUT-B and connection A is only applicable if you are using the CMOS version of the Si570 and not
the provided Si570 LVDS.
___________________________________________________________________________________________________________
Instruction manual KH-SDR wideband receiver Kit No-1021. All rights reserved KTH-SDR-KIT. Software design by PA0RWE.