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From: MoiInAust on 5 Dec 2009 12:45

"Schmidt" <sss(a)online.de> wrote in message
news:OAhbxoadKHA.1652(a)TK2MSFTNGP05.phx.gbl...
>
> "MoiInAust" <user(a)user.com> schrieb im Newsbeitrag
> news:4b1a2eba$1(a)dnews.tpgi.com.au...
>
>> > About 1-2MegaSamples per second is the maximum IMO
>> > for "normal" AD-digitizing over USB - and radio-
>> > frequencies are much higher than even that.
>> ...
>> ...
>> I wanted to read 455 KHz +- 10 KHz so it sounds like no go.
> Given my above statement, if you use for example this device-category:
> http://www.datatranslation.com/products/dataacquisition/usb/dt9832.asp
>
> Then you can capture a 455kHz signal at a constant rate of
> e.g. 2MSample/second (in 16Bit res.) - continously, since
> these expensive boxes stream their data over the fast USB2.0
> channel.
>
> There are also cheaper USB-based "oscilloscopes" available,
> which can work up to 50MHz - but the data from these
> devices cannot be transferred continously to your PC-
> software anymore - instead these "oszis" buffer shorter
> time-intervals of the internally high-frequently captured data -
> starting at a trigger-event - and what you get transferred
> to your PC (continously) are only the contents of these
> shorter time-frames.
>
> Just google around a bit - there are also "specialized forums"
> available, where hardware- (or electronics-) related questions
> are better placed.
>
> Olaf
>
Could you suggest such a forum? Also, although we are looking at the eg 455
KHz passband on an IF strip, I believe the data iteslf is much slower, as
the sweep is relatively slow, ie the speed of the sawtooth used to produce
it..


From: Martin Trump on 6 Dec 2009 08:14
Care to e-mail me? Too off topic for clvbm

I wanted to read 455 KHz +- 10 KHz so it sounds like no go.
From: Schmidt on 6 Dec 2009 09:03

"MoiInAust" <user(a)user.com> schrieb im Newsbeitrag
news:4b1a9c31$1(a)dnews.tpgi.com.au...

> Could you suggest such a forum?
Only from short googling for "electronics radio forum":
http://www.drmrx.org/
Would say, the guys there know very well, what you
want to achieve (working on the IF-result of a
HF-mixer "in software").
At least they should have better suggestion, where
to look elsewhere, to achieve your goals (just in case
they cannot help you).

> Also, although we are looking at the eg 455 KHz
> passband on an IF strip, I believe the data iteslf is
> much slower, as the sweep is relatively slow, ie the
> speed of the sawtooth used to produce it..
If that is more meant, with regards to the "price-point"
of such an "ready-to-use" 2MSamples-USB-device -
I'm sure there are also cheaper ones from other vendors.

If you want to save even more money on the needed
hardware, you could also develop a small board yourself,
there are so many nice micro-controller(eval boards) out there -
even the 32Bit ARM-based ones are not that expensive anymore -
with support for fast USB-transfers and with digital ports,
where you could bind the A/D-converter chip of your choice
....and with a little bit of C-programming you could bring such
a design to work then - or use prebuilt boards from people
who've been "already there" - would say the above mentioned
forum is a good place to ask all that.

Olaf


From: Dr J R Stockton on 6 Dec 2009 17:54
In comp.lang.basic.visual.misc message <4b1a2eba$1(a)dnews.tpgi.com.au>,
Sat, 5 Dec 2009 20:58:14, MoiInAust <user(a)user.com> posted:
>
>Thanks Olaf. I wanted to read 455 KHz +- 10 KHz so it sounds like no go.
>

If it is bandwidth-limited to 10 kHz then one can recover the waveform
by sampling at only about 10 000 samples/second.

--
(c) John Stockton, near London. *@merlyn.demon.co.uk/?.?.Stockton(a)physics.org
Web <URL:http://www.merlyn.demon.co.uk/> - FAQish topics, acronyms, & links.
Correct <= 4-line sig. separator as above, a line precisely "-- " (SoRFC1036)
Do not Mail News to me. Before a reply, quote with ">" or "> " (SoRFC1036)
From: Jim Mack on 6 Dec 2009 19:27
Dr J R Stockton wrote:
> In comp.lang.basic.visual.misc message
> <4b1a2eba$1(a)dnews.tpgi.com.au>, Sat, 5 Dec 2009 20:58:14, MoiInAust
> <user(a)user.com> posted:
>>
>> Thanks Olaf. I wanted to read 455 KHz +- 10 KHz so it sounds like
>> no go.
>>
>
> If it is bandwidth-limited to 10 kHz then one can recover the
> waveform by sampling at only about 10 000 samples/second.

Nyquist says you need at least two samples per cycle to adequately
recover the waveform.

--
Jim Mack
Twisted tees at http://www.cafepress.com/2050inc
"We sew confusion"

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