1) Place a jumper on the CLKSEL "I" pins (lower two pins of the three CLKSEL pins) on one of the Mercury boards; this will be the "master" Mecury board.

2) Place a jumper on JP9 (enabling the 122.88MHz oscillator) on this "master" Mercury board

3) Place a jumper on J5 (GPIO) pins 3,2 (MULTIPLE_MERC jumper) indicating that this board is to be used for multiple-Mercury board operations. All Mercury boards used for multiple-Mercury operations must have the MULTIPLE_MERC jumper in place. Place a twisted-wire pair (green wires) onto pins 4 & 5 of J1 (LVDS header) to take the 122.88 MHz clock out from this "master" board to other ("slave") boards via the LVDS J1 header connections.

For these three steps refer to the red rectangles in the photo below (photo courtesy of John Petrich W7FU), this board is now configured to be Mercury #1 (ADR = 0)

The jumpers (red rectangles) required to make the board Mercury #2 (ADR 1) are shown in the photo below (photo courtesy of John Petrich W7FU). Note that the 122.88 MHz module is disabled, making this board a "slave" board as far as the 122.88 MHz clock is concerned. This board receives its 122.88 MHz clock via pins 1 & 2 of J1 (LVDS header, green wires) from the board designated as "master", such as the Mercury #1 board shown above.


If you wish to have triple Mercury boards, the Mercury #3 board should be jumpered as shown below. This board is now configured to be Mercury #3 (ADR = 2). It should receive its 122.88 MHz clock via external twisted wire connection to pins 1 & 2 on J1 (LVDS, twisted-wire connection is not shown in this particular photo but it will be connected as shown for Mercury #2 in the photo above).

A Mercury board that is jumpered to be Mercury #4 (ADR=3; not shown) would have the jumpers as shown in the photo above for Mercury #3 plus an additional jumper on J5 between the two red rectangle jumpers shown on J5, making three jumpers on J5 for Mercury #4. As with the other "slave" boards, it should receive its 122.88 MHz clock via the LVDS header, as shown previously in the photo for the Mercury #2 board.

NOTE: If more than two "slave" Mercury boards are used, the 100-ohm terminating resistor, R20, should be removed from all but one (the last Mercury board in the physical parallel "chain" of connections) to minimize the load on the output pins of the "master" Mercury LVDS chip. The LVDS twisted-wire connections to all "slave" Mercury boards should be in "parallel"; i.e., pin 1 of J1 on each "slave" Mercury board should be connected to pin 1 of J1 on the other "slave" Mercury boards, same with pin 2 of J1. Pins 4 & 5 of J1 on the "master" Mercury will drive all of the pins 1 & 2 of J1 on the Mercury boards. The limit of two "slave" Mercury boards before needing to remove R20 on some of them is that the SN65LVDM180D LVDS driver chip can tolerate only two 100-ohm loads in parallel. If more than two "slave" Mercury boards are desired, it is necessary to remove R20 from some of the boards to keep the total load on the "master" Mercury LVDS output pins to no more than two 100-ohm terminating resistors total.

4) Place a jumper from the Atlas C16 pin to J8 (Aux Clk input) pin nearest the FPGA on the "master" board and all "slave" Mercury boards.

For step 4 refer to the photo below, the white arrow indicates the jumper from Atlas pin C16 to J8 (EXT CLK IN).


5) In PowerSDR, select Setup>Excalibur as the source for the 10MHz clock and Mercury for the 122.88 MHz clock.

With the jumpers in place as shown in the photos above, the 122.88 MHz oscillator on the "master" Mercury board will supply the122.88 MHz clock for the "master" and, via the LVDS headers on the Mercury boards, to the "slave" Mercury boards. These clock connections enable coherent operation of the multiple Mercury boards.

The photo below shows the K5SO HPSDR rig with three Mercury boards connected for coherent-receiver operation; the 122.88 MHz clock from the "master" Mercury board is connected via twisted-wire pair connections (blue and white twisted-pair wires) on the LVDS header to the LVDS headers on the two "slave" Mercury boards.