[hpsdr] Mercury diversity mode configuration

[Joe Martin K5SO]

Hi Luke,

Very good!

On Sep 3, 2011, at 11:14 AM, Luke Steele wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> At 07:16 PM 14/05/2011 +0800, Phil Harman wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> A better solution is to feed the 122.88MHz clock from one board to  
>> the other
>> via a short twisted pair using the LVDS transceivers on the Mercury  
>> board.
>>
>
> I have a second Mercury card on its way from iQuadLabs.
> Is the 122.88 MHz clock jumpering mentioned above and detailed in  
> the HPSDR
> Wiki all I need regarding clock signals?
You will need a 10 MHz clock source for the Mercury boards, of  
course.  Mercury has an on-board oscillator but it is best to disable  
that by pulling it's power jumper and instead use a common 10 MHz for  
both boards from the Atlas bus if you have an Excalibur board to  
provide the 10 MHz clock.


> Is an external reference clock to the Atlas bus, such as Excalibur  
> also
> required?
Not absolutely, as I mentioned, but it is preferred to do so; the  
clock on Excalibur is more accurate than the ones used on the Mercury  
board and, if you supply Excalibur with a high accuracy external 10  
MHz reference from a rubidium vapor standard or a GPS standard, things  
are even better.  Actually, I haven't investigated how the Mercs  
behave with the diversity programs if you use the on board 10 MHz  
Mercury clocks and don't have a common one; I've always used a common  
10 MHz clock as well as a common 122.88 MHz clock.

> What antennae are Diversitites using (for HF)?

Any two antennas you happen to have available will work, to a degree.

To be optimum, the antennas you use depend upon what kind of  
"diversity" you are seeking.  For example, if you are wishing to  
achieve polarization diversity then you would connect orthogonal  
polarization antennas, one to each Mercury.  If, on the other hand,  
you wish to achieve "spatial" diversity and perform antenna pattern  
steering, you would connect two spatially separated antennas.

FYI, I am currently writing a "steering" PSDR program to allow one to  
use two or three identical antennas in a line for directional steering  
via the PSDR program.

For starters with the diversity programs you need not have identical  
antennas in order to be able to achieve strong nulling and directional  
steering functionality.  The "direction" you steer to will be unknown  
to you however and not calibrated in this case but using diversity in  
this way is still fun to do and provides useful signal nulling/ 
enhancement capabilities.  Indeed, the "direction" is not shown on the  
dual-Mercury program as the program does not have sufficient input  
regarding the user's specific antenna system to be able to calculate  
the direction of sensitivity in real space; neither does the current  
three-Mercury program for that matter.  The next version of PSDR I  
post WILL have such calibrated directional capability, though.

> I'm sure I'll have other questions, but the above remain after reading
> through all the messages on the topic this year.
> Regards,
> Luke VK3HJ

Good luck to you!  I'm happy to hear that you're joining this aspect  
HPSDR!

73,  Joe K5SO



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