[hpsdr] Hermes design thoughts - local processor - the Hawkboard

[Steven B. Dick]

One more thought.  I came across an interesting development board called the
Hawkboard. See  http://www.innovatesolutions.net/products/hawkboard

This little beauty cost $94.00.  Has a USB and 10/100 Ethernet interface and
VGA interface, SATA inteface, a OMAP L 138 Application Processor (>300MHz
-ARM 926 & 300MHz C674X floating point DSP, and small form factor
-90mmX100mm. It has a large user community as well.  This could satisfy my
"self-contained" idea at relatively low cost.
 
Regards,
Steve, K1RF

-----Original Message-----
From: Phil Harman [mailto:phil at pharman.org] 
Sent: Thursday, August 05, 2010 11:15 PM
To: Steven B. Dick
Cc: hpsdr at lists.openhpsdr.org
Subject: Re: [hpsdr] Hermes design thoughts

Hi Steve,

Thanks for your interesting feedback.


> preamp, etc. I also looked at a QS1F front end discussion. My 
> conceptual design would have used a 1.6MHz high pass filter (always 
> in) to eliminate strong AM broadcasts if you happen to live near one) 
> followed by a 60MHz high pass filter (always in) followed by a 
> programmable 0-31.5db HMC472 Hittite attenuator which allows 0.5dB 
> attenuation steps followed by a mini-circuits GALI-74+ preamp (always 
> in) followed by a 6dB resistive pad attenuator to cut the gain down 
> some on the high gain preamp.  This would eliminate any relay 
> switching, provide finer control of RF attenuation while trading off 
> maximization of IP3 (would need additional FPGA I/O and associated 
> firmware).  I would not add any other filters,  to minimize complexity 
> and to depend on the inherent filtering of the antenna itself.
> I

This is something we will look at. I'm not so sure about the 1.6MHz HPF
since I use my Hermes to monitor NDBs and I'm sure there are others who
would like to monitor the MW bands.

I prefer balanced preamps to assist with IP2 issue - particularly since we
open up the front end to the entire HF spectrum.

The HMC472 looks interesting assuming that the IP3 is acceptable.

73's Phil...VK6APH

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