[hpsdr] Hermes

[jim goldenberg]

Gigabit PHYs are hot and can be noisy/  Ethernet is OK but not if it injects 
noise into the product.  I'm the chief engineer for a single board rugged 
computer company serving the mil/aero market.  Most of the problems I get 
involved with are EMI issues around the Ethernet interface and is almost always 
a layout issue with Ethernet PHY and  signals going off board and out of box. If 
you do it be very careful.  Good luck

JimG - N1KWZ

Phil Harman wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> All,
>
> Having completed the Beta testing of Hermes we are now preparing to make
> the necessary changes to bring the board into a production ready state.
>
> There are quite a few changes which are mainly due to the fact we want to
> ensure the product lives up to the 'High Performance' name tag.
>
> One of the changes is to replace one of the high current linear regulators
> with a SMPSU. We are fortunate to have Kjell, LA2NI,  on our design team.
> Kjell has designed a high frequency SMPSU that works well when
> incorporated on the Hermes PCB and does not introduce significant spurs.
> This substantially reduces the current drain and also the heat
> dissipation.
>
> The other potential change is this.  I have this week build a prototype
> OzyII Gigabit Ethernet board. It works very well and I'm impressed with
> how rugged Ethernet appears to be in comparison to USB and Firewire.
>
> We therefore have the opportunity to replace the USB interface on Hermes
> with Ethernet.  There are a number of advantages in doing this:
>
> - we overcome the USB driver issues when using different operating systems
> - we can 'network attach' Hermes
> - we will have a very high speed interface to the board for future features
> - we can use a much longer Ethernet cable than USB allows
>
> the disadvantages
>
> - it may need more that one spin of the PCB which will delay the delivery
> - we will use approximately 10% of the FPGA to implement the Ethernet
> interface.
>
> I'm not too concerned about using more of the FPGA since the device we are
> using is 70% larger than that used on Mercury.
>
> So "to USB or not to USB - that is the question"?
>
> 73's Phil...VK6APH
>
>
>
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