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RE: [linrad] SDR Hardware
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:
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.
and I
suggest you join the forum and see all of the musings, etc.
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:
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
and the upcoming USRP (Universal Software Radio
Peripheral)
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
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