[hpsdr] Multi-RX using TAPR-Mercury and Mercury-EU

[Joe Martin K5SO]

Hi Alfred,

Very good!  I'm pleased to hear that you are going to try out  
diversity mode operations.  Although I do not have a Mercury-EU board  
here to verify my following suggestions (perhaps someone who does can  
confirm the accuracy of this), from the photo of the -EU board you  
referenced it seems to me that all of the essential jumper blocks, etc  
are present on the -EU board to set up the board for diversity  
operations.

Specifically, to set up the -EU board for diversity, I believe you  
will need to:

1)  Jumper the GPIO header pins to set the board address to either  
address "0" or address "1" depending upon which you wish the -EU board  
to be.  Address "0" will require 1 jumper on the GPIO header, as  
described in the Wiki for the TAPR board, and address "1" will require  
2 jumpers on the GPIO header.  I imagine that the header is oriented  
such that the lowest number pins are at the bottom of the header and  
the highest number pins are at the top.

2)  In the photo of the -EU board, Q10 does not appear to be installed  
on that board.  I believe that Q10 on the -EU board must be the 122.88  
MHz oscillator module that corresponds to U1 on the TAPR board.  If  
your -EU board has Q10 installed then JP4 should be in the "Q10  
installed" position" and nothing further need be done with regard to  
the 122.88 MHz clock on the board.

However, if your -EU board does not have Q10 installed then the board  
is likely getting its 122.88 MHz clock via the LVDS input header on  
the -EU board from the 122.88 MHz clock on the Penelope board.  In  
this case you have a couple of options.  The idea for dual Mercury  
board operations is that the 122.88 MHz clocks on both Mercury boards  
should be phase locked to the 10 MHz clock signal that appears on C16  
of the Atlas bus.  One option is to obtain the 122.88 MHz clock for  
the -EU Mercury from the TAPR Mercury board via the LVDS input header  
pins (using an external jumper between the -EU and TAPR Mercury  
boards) on the -EU board and the center pin of the "CLKSEL" header on  
the TAPR board.  This option requires a jumper between the Mercury  
boards for the 122.88 MHz clock.  An alternative option that does not  
require a jumper between the Mercury boards would be to phase lock the  
122.88 MHz clock on Penelope to the 10 MHz clock on C16 of the Atlas  
bus.  I've not investigated this option so I don't know for sure how  
straightforward that is to do but I'd be happy to work with you in  
resolving the issue.  A third option, of course, would be to obtain  
and install Q10 and use it as the 122.88 MHz clock for the -EU board.

3)  Jumper the pin of the "AUX CLK" header that is connected to pin 89  
on the FPGA to Atlas bus line C16 by using a wire jumper placed on the  
back side of the -EU board between those two points.  This provides  
the 10 MHz clock (from Excalibur) to the FPGA.

I think performing the above steps should fix you up.  Of course, if I  
haven't been very clear in my explanation above I'd be happy to work  
with you directly to get your board up and running in diversity mode  
with more detailed help.  Hopefully I have interpreted the photo of  
the -EU board correctly.  If not, perhaps someone with a -EU board can  
straighten me out.

Let me know if I can be of any help!

73,  Joe K5SO


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