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Hi Alberto,
Thanks a lot for answering the questions so
fast and so late in the night....!!
Well, I'm using the software since a couple
of days with my AD831 interface, comparing the reception with my SGC transceiver
and I should confess that it sounds great.
It takes a while to adjust the band pass
and denoiser.
Denoiser works well but the audio level decreases a lot. The
"low" position is my favourite.
The 96kHz sampling does not work properly
with my sound card, there is a kind of modulating hum and the audio is not so
good as it is using 48kHz.
My sound card is a VIA
AC97.
The other topics concerns the transmit side
of the software....Do you plan to implement something using the sound card as a
mike input to deliver I and Q signals ?
It woud be fine to be able to build a
transceiver interface.
If not, I plan to develop the transmitting section
using classic hardware.
Have a good day,
Best 73,
Gérard
----- Original Message -----
Sent: Thursday, July 21, 2005 12:45
AM
Subject: [soft_radio] Back from
vacations
Hi all,
I am back from a few
days of vacations, and I have found some questions to
answer.
> Who someone knows what are
the "WF", "SP" and "Dec" button on the
> right side
?
They are just placeholders
for new functions. WF stands for Waterfall, SP for Spectrum and Dec for
Decoder.
These functions probably will not ever be implemented, as I
am working on a new program that in my intentions
should superceed SDRadio.
Due date, October time frame.
> 2 -
the calibration sound card was impossible until I put a 47k pot in
> one
of the 2 outputs, the amplitude control had a very small effect
> before
that.
The amplitude control
in the Skew adjustment panel has a limited range on purpose, to make it easier
to find a null.
I had reckoned that the generally the amplitude unbalance
between the Left and Right channels is small, and a +- 5%
adjustment should
suffice. In your case this my assumption seems to not
hold.
> At -130dBm from my generator,
the signal level on the display is -110dB
The level reported by SDRadio is of course a relative one, as it
depends, among other things, on the settings of the
Windows mixer, the
setting of the volume knob of your hardware. etc. What is important is that,
for a change of xx dBm
of your generator, the display of SDRadio shows an
equal amount of change in the displayed dB.
> 5- The denoiser is very useful but quite
desorienting...,it really
> cleans the noise from audio and listening is
more easy.
> However, there is a significant loss of audio level when it
is IN and
> the global S/N remains about the same. The audio gain
(control panel)
> has to be increase merely to recover the same audio
level in the loudspeakers.
The
denoiser is based on the Widrow-Hoff method, and its results depend on some
parameters that enter into the
equations. I chose them just by trial and
error, listening at the filtered audio. They have changed from V0.94 to V0.95,
and I have been told that V0.94 worked better... probably in the new
program I will make them user-selectable.
> 7- Band pass :
> The reduction of the band
pass (ie CW mode) does not appear very
> attractive, the audio sounds
rough and the improvement is not obvious
> in my
opinion.
I am not sure I follow you. SDRadio does not have an
explicit CW mode. The two sides of the receiving window are
individually
draggable to be placed just below and just above the CW signal of interest.
When doing this I found that
the filtered CW signal is very clean and free
of QRM/QRN. But maybe I have misunderstood you.
> S1 =
-87 dBm
> S2 = -76 dBm
> S3 = -67 dBm
> S4 = -60 dBm
>
S5 = -54 dBm
> S6 = -47 dBm
> S7 = -40 dBm
> S8 = -33
dBm
> S9 = -26 dBm
> "S10" = -20dBm
An interesting chart, thanks for having
measured it. But please note that the markings on that level indicator are not
meant to be S-Units. The meter just shows the averaged amplitude of the
incoming signal, evaluated on a buffer-by-buffer
basis, on a logarithmic
scale. With some additional effort it could be modified for an S-unit scale,
though.
> I wonder if the I/Q
output is really a major advantage instead of
> single channel.
>
Using I/Q output, does the sideband selection is provided by the
>
software or must I add a sideband switch ?
It all depends
whether your hardware has a mean to discriminate the wanted from the unwanted
sideband.
If you have already suppressed the unwanted sideband, the only
advantage that I/Q processing gives you is a doubling
of the received
band, i.e. sampling at 48 kHz will give you 48 kHz of useful range, not the 24
kHz that you would have
with a mono input (remember Nyquist).
On the
contrary, if you cannot suppress beforehand the unwanted sideband, like in a
DC (zero IF) or near-DC receiver,
then the I/Q processing is the only
way you have to get rid of it, up to 70 dB of rejection, with a proper
balance.
The selection of which sideband to keep is done by the
software.
Ok, maybe I have other messages to answer to, but I will
leave that for tomorrow. It's almost 1 AM, and I am sleepy...:-)
Good
night
73 Alberto I2PHD
YAHOO! GROUPS LINKS
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