[hpsdr] JanOz-163 and SDR-1000 without INA163

[Ahti Aintila]

Hi Bob,

I am really satisfied with the performance of Janus working without
the INA163. Just a minor correction to avoid more confusion. I
reported the noise floor being -147 dBm/10.7 Hz. That is incorrect
because actually we are using 48 kHz sampling and 4096 bins and that
calculates to -147 dBm/11.7 Hz noise density. Sorry for the error.

When my other activities allow, I want to build a separate RX hardware
with its own DDS (possibly AD9951) and a new sampling detector
according to the principles we have been experimenting recently with
Marco IK1ODO.

73, Ahti OH2RZ


On 30/05/07, Robert McGwier <rwmcgwier at gmail.com> wrote:
> Ahti Aintila wrote:
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Phil,
> >
> > Today I tried the balanced I/Q input to Janus taking the signals
> > directly from the sampling capacitors and without any amplifier. The
> > connecting cable was 1 meter long Cat 5e with 4 twisted pairs. The
> > unused pairs and the shield wire were connected to ground at both
> > ends.
> >
> > The result are promising:
> > - testing frequency 3.7 kHz
> > - RFE included, no attenuator used
> > - noise floor -147 dBm/10,7Hz, Blackman-Harris window
> > - noise -132 dBm/500Hz
> > - no compression/clipping at -7dBm (max signal of my generator)
>
> This is very good news.  It will be a direct increase in dynamic range.
>
>
> >
> > I had a lot of spurious signals visible, obviously due to common mode
> > and poor shielding of the cable. The spurious level was dependent on
> > the cable position on my working desk, so obviously better results can
> > be achieved with a more professional test set-up. Now I tried to
> > position the 500 Hz filter to the best position between the spikes.
>
> Why just use a twisted pair forcing all external signals to be common
> mode and eliminated so long as they do not clip the input amplifiers?
>
> >
> > Thanks for the good work!
> >
> > 73, Ahti OH2RZ
> >
> >
>
> Nice job indeed.
>
> Bob
>
>
> --
> AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
> TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
> "If you're going to be crazy, you have to get paid for it or
> else you're going to be locked up." Hunter S. Thompson
>

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