[hpsdr] Project proposal - Hermes

[Steve Bunch]

On Apr 15, 2009, at 8:52 AM, Philip Covington wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
> On Sun, Apr 12, 2009 at 12:35 PM, Kevin Wheatley  
> <m0khz at tiscali.co.uk> wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>>
>>
>> Following the outstanding success of Mercury and Penelope, and  
>> while investigating the verilog code for both, I had the insane  
>> idea of merging the verilog code of Mercury and Penelope into a  
>> single fpga! I played around with this idea for a while and the  
>> more I thought about it the more I liked the idea.
>> So here is the proposal, to develop a single board HPSDR based on  
>> the hardware of Mercury and Penelope and a single large fpga.
>> This board would have PC connectivity by USB. I’m planning to  
>> squeeze this all onto Euro Card sized PCB (100 x 160 mm), and if I  
>> utilize both sides I might even have room for a Pennywhistle type  
>> PA  :).
>> Basic specs so far (nothing cast in stone)
>> Fpga EP3C25Q240C (I think this is the largest without BGA pin out)
>> Mercury receive chain
>> Penelope transmit chain
>> USB2 to PC data transfer
>> Pennywhistle PA (if there’s room)
>> 10Mhz on board with ext an option
>> Alex filter switching header
>> 13.5V supply
>> I’ll post a provisional block diagram on the Wiki this week, and  
>> lastly, why the name?
>> Following the tradition of the HPSDR naming convention, I thought  
>> Hermes was appropriate as he was known for his invention and theft!
>> All comments welcome.
>> Kevin – M0KHZ
>
> While interesting, this proposal does not fit in with the rest of the
> HPSDR projects.  It does nothing to advance HPSDR because it is a
> rehashing of boards that have already been produced.  The idea behind
> HPSDR was to break the projects up into modules that could work on a
> common bus (ATLAS).  By breaking it up into modules, multiple people
> could work toward a common goal.  There is also a (project leaderless)
> proposal for an Ethernet based OZYII board now - how does that jive
> with your stand alone board proposal?
>
> The other issue is that this will necessarily require different
> firmware, software, and FPGA HDL than the individual modules it
> combines.  What about those who have invested in Atlas, OZY, Mercury,
> Penelope, etc..?   Will development be slowed or stopped for those
> people if favor of the this new board that combines all the work of
> these individual projects into one?
>
> Phil N8VB

It took me many months to get my Atlas/Ozy/Mercury/Penelope board set  
installed in a chassis with room for amplifiers and transverters,  
updated, and up and running with PowerSDR, but it finally happened and  
it works great!  I'd like to thank all the people who invested their  
time and effort into making those projects happen -- they are heroes!   
But there is a big difference between "boards to use for  
experimenting" and "turnkey" radio operation.  I do both, and I  
suspect others do too.

The HPSDR project has not been about self-contained SDR's like Hermes,  
but I suspect that many of the people who've bought board sets to use,  
rather than to experiment with h/w, would be at least as well-off with  
a single board that has a subset of the capability of the HPSDR  
boardset.  This is by no means a negative statement about the use of a  
common bus that people can experiment with -- it's a great  
modularization and experimentation concept (I used to make my living  
off of the VME bus!).  You can, at least theoretically, put multiple  
Mercury's in a system with one Ozy/Penelope, for example.  But once  
you have experimented enough with separate modules to know the core of  
what you want, you can consolidate that into one board for space and  
cost efficiency, and then jump off from there to other realms of  
experimenting.  If Hermes had an Atlas connector, and you could put  
multiple of them in an Atlas sharing a single USB port, you could make  
it look like multiple Mercury's, multiple Penelope's, both at once, or  
something completely different -- with only one unique board to  
manufacture.  And a single slot per Rx/Tx/"Ozy".  Without the huge  
effort that went into Atlas/Ozy/Penelope/Mercury, this would be a  
massive project -- but now, it's largely an integration and reuse  
activity.   (Back in my VMEbus days, we made CPU boards, memory  
boards, many different I/O boards, and single-board-computer boards  
that combined a subset of all those onto a single board.  The single- 
board-computers were far-and-away the most popular.)

If the software interfaces can be made the same, then that would be  
the best of all worlds... if not, it's going to be a bigger software  
effort.  So one approach would be for the Hermes to interface exactly  
like a "combined Ozy/Penelope/Mercury subset", so loading the Hermes  
rbf instead of Ozy rbf would be the first but only difference seen by  
the PC software.  That may not be perfectly achievable, but the closer  
you get, the less work you make for people like Bill Tracey.

Specifically w.r.t. the Hermes proposal, putting even a moderate-power  
transmitter onto the board will generate some noticeable power and  
grounding demands, both to avoid noise pickup on ground loops (maybe  
even worse if you happen to have a high VSWR), and to get wide enough  
traces all the way back through Atlas to the power supply to avoid  
voltage drops on busses.  It might be better to keep power  
amplification off the bus.  Oh, and since it might be mounted  
standalone: please leave a large-enough keep-away area around the  
mounting holes that a nutdriver clears nearby components.  Not that  
anyone would be careless enough to crush a capacitor or anything, I'm  
just saying...  ;-)

Steve, K9SRB



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