RE: [linrad] SDR Hardware

["Robert McGwier" <rwmcgwier@xxxxxxxxxxxxxxx]

The R2Pro or the SDR-1000 are both good ways to do some software defined radio.

I will point out again for you a design flaw in the SDR-1000 that I pointed out a few

days ago here, maybe you missed it.  The INA's, the instrumentation amplifiers,

provide most of the SDR-1000 system gain.  They are AFTER the sample and hold,

mixer (which some call the Tayloe Detector, Gerald calls the Quadrature Sampling

Detector).  This means that the signal of interest from the antenna is added to the

phase noise and spurs and thermal noise of the QSD before the signal is amplified.

It is clear that this is wrong to have all of the gain after.  You have competing

interests here: linearity and noise figure.  If you move all of that gain out in front

of the mixer, then the demands on that preamplifier/front end become quite

demanding since it must operate from 0 to 75 Mhz and be very linear with good

IP3, etc.  My current best mix is 20 dB out front with 6 dB after using a GALI-6

in front of the mixer.  This was recommended to me by Mike Cresap, W3IP

and it has been a good performer.

 

With the R2Pro, there is more hardware hands on to do:

 

http://www.seboldt.net/k0jd/

 

and with the SDR-1000, after the dust settles on re-doing the front end, and

possibly adding better filters for ham band coverage,  all the work is

software.  Currently, all of the work going on on the SDR-1000 outside of

a couple of people is being done in the software arena.

 

http://www.flex-radio.com

 

and I suggest you join the forum and see all of the musings, etc.

 

 

http://www.flex-radio.com/forum

 

In addition to this, Gerald's resource page is very helpful.

 

Also, the DSP-10, with the recent additions by Lyle KK7B make for very

interesting SDR work:

 

http://www.tapr.org/tapr/html/kitsf.html

 

and the top three listings are for the DSP-10 and the KK7B DSP add on module.

This same module is the new DSP module that Elecraft is offering for the

fabulous K2.

 

GnuRadio

 

( http://www.gnu.org/software/gnuradio/gnuradio.html )

 

and the upcoming USRP (Universal Software Radio Peripheral)

 

http://mail.gnu.org/archive/html/discuss-gnuradio/2003-08/msg00062.html

 

 

 

 

It is a very exciting time for receiver work in ham radio with Linrad, SDR, GnuRadio

are really changing the way we think about receiver work and homebrewing

receivers.

 

For my money, having done all of the above, the potential for the QSD (Tayloe

detector) is extremely large.  The numbers I can measure in the lab tell me

that with careful design work, this can be the basis for the greatest receiver

in all numbers.

 

Bob

 

 

 

-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxxxxxxxxx [mailto:owner-linrad@xxxxxxxxxxxxxxxxxxxxxx]On Behalf Of J. Michael Thurman
Sent: Friday, December 12, 2003 7:47 AM
To: linrad@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx: [linrad] SDR Hardware

Greetings.  I have been reading the list for a while and am excited about the possibilities presented by sdr.

 

I have read the recent QEX articles on sdr and many others on the ARRL sdr page.  My question is this: what is a your recommendation for a homebrew SDR hardware platform?  I can use the designs Leif presents and the design for the SDR-1000 as a basis...but I really want some more thought from those of you who have the system running before I dig in.   Most of my operating is HF SSB, CW, and PSK. 

 

73

Michael

WN5T

LINRADDARNIL