32907RE: [softrock40] Re: Netbook computers and SoftRock
- May 1, 2009Sorry to post again so soon, but I did a couple of quick tests.
The good news is that the audio input to the Acer Aspire One is indeed
STEREO. I was able to plug a SoftRock into the input, and after messing
with the Realtek mixer settings a little, turn off the internal mic and turn
off the mic boost.
The very bad news is that there appears to be a SERIOUS 8KHz lowpass filter
between the input jack and the audio A/D. If you fire up Rocky, you will
see a large noise hump plus/minus center freq that is 16kHz wide (+/-8kHz)
45dB above flatline. The rest of the spectrum is a flatline, except for
some image spikes. So, you could use the Acer internal sound chip if you
don't mind seeing only 16kHz worth of the band. Sounds like the first-gen
iPhone all over again!!
I was not able to obtain decent image suppression using a signal generator
to calibrate Rocky (3.6). The images seemd to be fixed at about 30dB below
the actual signal. However, I saw few images of real-time signals when
connected to an antenna. Also, I got several debug errors from Rocky during
the image calibration attempt. There is definately some image suppression,
and the signal generator shows a definate 16kHz-wide reception bandwidth.
This means the input is really stereo.
Listening to the unit on 40M SSB, I had to turn off the Rocky AGC, and
manually run the level down. Probably because of the huge difference
between the flatline area, and the LPF passband. The demodulated audio
seemed a little distorted, but that was likely due to manual RF level
setting. I was using external speakers.
Others have opened up their Acer Aspire Ones to do mods (see the Aspire One
user groups), but I'm not ready to do that just yet. I have enough other
projects at the moment. Maybe someone else can open it up and find a way to
bypass the audio LP filter?
> -----Original Message-------
> From: Rob Frohne [mailto:frohro@...]
> Sent: Friday, May 01, 2009 12:48 AM
> To: firstname.lastname@example.org; wb4jfi@...
> Subject: Re: [softrock40] Re: Netbook computers and SoftRock
> Hi Terry,
> What sample rate do you get with your Acer? Did the sound card work in
> Ubuntu? Is it true stereo in, and how is the sound card for S/N?
> Thanks & 73,
> Terry wrote:
> > --- In email@example.com
> > <mailto:softrock40%40yahoogroups.com>, "Kees & Sandy" <windy10605@...>
> > wrote:
> > >
> > > Is anyone using one of the inexpensive 9" netbook computers with
> > Softrock and Rocky ? I'm in the process of bringing a Dell 910 up.
> > > 73 Kees K5BCQ
> > >
> > I'm using several SoftRocks (at different times) and Rocky 3.6 on an
> > Acer Aspire One Netbook. The Aspire One has the larger hard drive and
> > XP on it. SoftRock RxTx 6.3 (with & without USB control), RxTx 6.2, SR
> > Lite 6.2, and Brainerd DDS/QSD board all used.
> > I've played with a few different "cheap" USB sound cards, and one
> > Extigy USB sound card. No transmit yet. The cheaper USB sound cards
> > have more spurs, but are OK for demos & software testing.
> > I'm about to dual-boot the netbook with Ubuntu 8.04 as well.
> > Terry
> > WB4JFI
Rob Frohne, Ph.D., P.E.
E.F. Cross School of Engineering
Walla Walla University
100 SW 4th Street
College Place, WA 99324
(509) 527-2075 http://people.walllawalla.edu/~rob.frohne
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