RE: [linrad] I-Q and HF SSB/AM/FM questions, bulk buy for 200Mhz SAW oscs

["Robert McGwier" <rwmcgwier@xxxxxxxxxxxxxxx]

Alex:

Right now, the primary deficits in the SDR1K system are the software
side of the house.  We don't have all of the modes/DSP software
tuned correctly yet.  I am not really familiar with the Linrad
hardware so I can make no direct comparisons.  The SDR1K does
not lack for dynamic range but your efforts will be hampered
by 16 bit A/D's in your sound card.  The SDR1K's dynamic range
is dependent on closed loop control of the gain settings in
the radio to optimally fill the 16 bits in the A/D on the
sound card.  If you can find a 24 bit A/D and a working driver,
that will be good (SB Live Audigy2 is one, I will not speak
for the quality of its A/D sample clock oscillator however).

I use my SDR1K for SWL as well and have recently modified the
software to output a DRM stream which works very well indeed
with the DRM and DReaM software.  The SDR1K software also has
a fully synchronous AM detector and a PLL based FM detector that
I wrote.  It has Adaptive LMS Noise canceller, I just added
an adaptive notch filter,  and will be implementing an automatic
pulse interference suppression scheme as in Linrad.

The issues we are dealing with are understanding the spur production
behavior of the AD9854 and always land on those frequencies
that produce minimum spurs (power -98 dBc, that is 98 db below
the primary carrier power).   I also believe the manufacturer
needs to halve the DDS output power to the mixer.  The SDR1K
is a fine experimental transceiver (receiver) but is in its
infancy in terms of software.  The software, like Linrad, is
all open source so you will be able to work on your own.  AB2KT
and I are contemplating  Linux versions of the software and will
use Qt for the GUI interface if we decide or Perl/Tk so we can
escape the limitations of SVGA on Linux and the severe limitations
in terms of multithreading on Visual Basic which the current SDR1K
software uses.

I think Linrad got the horse directly in front of the cart when
the software was worked on in great detail by Leif before his
articles came out.  In the SDR1K, there is no aspect of the
software (if you intend using it), that does not need attention.
I am very impressed with the Tayloe filter/mixer.  I am sure
we will see version 2 of the hardware sometime but I am having
a lot of fun with version 1 and the software gives me plenty
to do.  The DSP in both of these "products" is by far the
most interesting aspect of these projects.  Being open source,
there is lots of things to be learned from them and you can
add to the mix yourself or customize it for your use as I
have done.

I am getting ready to experiment with Linrad since I finally
got a decent sound card for my linux machine and got the
alsa drivers going (they have OSS compatibility modes so
that is not a problem).

Finally let me emphasize both of these projects are for experimenters.
If you want to take an incomplete project and "make it your
own" both of these are for you.  I still can't believe my
luck in renewing my QEX subsciption after years of absence
and having both Linrad and SDR1K in the same issue!

Bob
N4HY


-----Original Message-----
From: owner-linrad@xxxxxxxxxxxxxxxxxxxxxx
[mailto:owner-linrad@xxxxxxxxxxxxxxxxxxxxxx]On Behalf Of Alex Crow
Sent: Friday, July 04, 2003 18:08
To: linrad@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: [linrad] I-Q and HF SSB/AM/FM questions, bulk buy for
200Mhz SAW oscs


Roger,

What do you feel are the deficits of the SDR-1000 as compared to the Linrad
hardware? Is it in the dynamic range or elsewhere? As I am interested more
in
the SWL/General Coverage side of things will I be disappointed? I felt that
it was more flexible for covering the entire band from VLF-High SW. I
remember picking up a Liberian rebel station on my 2-diode single balanced
mixer RX back in my youth and I was elated - EME would be almost dreamlike!

Thanks as well for pointing me to your guide. I've just now posted all
manner
of dumb questions on the list to Leif and suddenly your pointers for my
"idiot's guide" came in.

BTW for all that have tried it I have the SB-16 PCI using ALSA's snd-ens1371
driver.

Many thanks.

Alex





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