A new twist on SDR...
metavox at earthlink.net
Mon Jun 5 20:47:38 CDT 2006
Now we have several options each with its strengths and costs.
At the bottom of the heap is the TenTec RX-320. It is cheap ($320) and
provides a lot of bandwidth choices with a simple, very simple, computer
interface. It does not do advanced processing. However the audio
output can be further processed in a PC for DSP noise reduction or
waterfall spectrum displays. It can also be modified to provide output
to the PC for Digital Radio Mondial. I have one and it is a fine
choice. It is a mature design and follow-on improvements are limited by
the onboard DSP processor speed.
Next is Gerald Youngblood's SDR-1000 Flex-Radio where the radio
converts the signal down to the audio range and the processing is done
in a PC. This has more flexibility but needs a good PC and costs are
higher ($500-1000). It can do higher bandwidths than the RX-320 and has
good performance. An option can be added for a software defined
Then there is the SDR-14 from RFSpace. This one can sample the whole HF
spectrum from .05 to 30 MHz and provide a spectral display of the whole
enchilada. In addition, you can record a 150 kHz slice of spectrum to a
hard drive for later playback and analysis. But this gets more
expensive than the previous two ($1000). Bill Farmer has used this as a
backend for an R7000. The spectral displays are pretty nifty.
Now we have the USRP with modules for different transmit and receive
ranges. Not much info on the web site as to just what it is. I would
like an A/D converter that can handle DC to light and a specialized
processor to handle and process the output of the A/D so the result is
as good as a high grade receiver. I doubt we are here yet. We should
keep our eyes on the web site and wait until the details (its supposed
to be an open design) are posted. Right now the download page has no
links to download the details.
In addition, there is LINRAD software which can do a lot of things but I
am not too familiar with that segment yet. It does work with the SDR-14
and with the Weak Signal Equipment (WSE) converters plus a lot more.
The WSE gear evolved out of EME needs. See
Terry Fox and Hal Feinstein talked about some future signal design work
at the last meeting. I spotted a pile of Dell Pentium III 600 MHz
computers missing memory and hard drives at the Manassas Hamfest and I
was offered all 5 of them for $5 each. These might make a common
platform for some sort of HF signal development effort. I am sure there
are many more such "opportunities" out there if we want to pursue it.
First we need to look a bit more into the radio options before adopting
such boatanchors. I am hoping a corporate computer user may dump a pile
of nearly identical computers with Pentium III processors at 600+ MHz.
Those should do some serious signal processing under LINRAD. I doubt
the WSE hardware is needed for the initial HF work.
Enough for now and thanks to Kevin, KE3VIN for the link.
Kevin P. Inscoe wrote:
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