Graham and Tobias,
Thanks for all of the information, I'm looking forward to implementing the
options that you mentioned.
73, Jim AA5BW
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Graham
Sent: Friday, August 15, 2014 7:49 PM
To: [email protected]
Subject: Re: LF: USB Sound Card?
Thanks for the run down Tobias
The windows re-sampling caused problems with wspr in the early days on
MF , as its possible that wspr had never been used in a situation
where 100% of the signal arrived at the RX . qsb was normally part of
the process ..
This caused a strange problem . where strong signals failed decode ,
where as low level with qsb did
It eventually transpired , that the sampling rates where not quite the
same on all systems and the short bursts masked the timing
differences , tested by sample audio files and a stop-watch
Later , we found Opera / Ros [ ros was first] that decodes failed with
other software running , additional routines where added to ensure the
sample rate was held at the correct speed , since then , all has been ok
I used soundblaster 5.1 external usb card , can be picked up s/h now on
ebay for very little
73-G,
G0NBD
--------------------------------------------------
From: "Tobias DG3LV" <[email protected]>
Sent: Friday, August 15, 2014 11:27 PM
To: <[email protected]>
Subject: Re: LF: USB Sound Card?
> Hi Jim, Gary !
>
> Experiences with Software Defined Radios ("Softrock" type) over years
> showed me the highs and lows of using a soundcard as an A/D-converter
> for HamRadio use. The situation improved from using the
> onboard-devices to professional external Firewire- or USB-2.0
> soundcards as they became available at reasonable prices.
>
> to A) it's true, the windows type drivers support up to 16 Bit only.
> There are some issues to sampling rate stability under windows, too.
> That's why SDR-programs like Winrad, HDSDR etc. use the alternative
> "ASIO" driver model, where 24 Bits are supported natively and where
> the latency is smallest. ASIO drivers typically are bundled with
> (professional) soundcards for studio-recording. I had the usual
> "EMU-0202-USB" card, which was sampling at 192kHz/24 Bit. As this is
> available no longer, today I use an "Icon Cube" and "Icon Cube pro"
> (2/4
> Channel,192kHz,24Bit,USB-2.0) for my softrock SDR. They are not too
> expensive and do a good job!
>
> to B) Windows has different properties for the hardware sampling rate
> and the offered (simulated) sampling rate. If these are not identical,
> there is a software up/down-resampling done by windows. You have to
> set the correct sampling rate at the hardware-settings (!) of the
> chosen soundcard input/output. (sometimes Win7 resets this to 44.1
> kHz/16Bit at another booting, so you have to check this first after
> booting up the PC.) e.g. Even if the soundcard is just sampling at
> 48kHz, the windows drivers offer 96 and 192 kHz as well, but actual
> audio-data is still not more than 48kHz, the rest of the spectrum is filled
> with "blanks".
>
> to C) Typically the anti-aliasing filters of a soundcard are bound to
> the current (hardware-) sampling rate (=Nyquist) and not be static.
> Those filters are digital ones and part of the A/D converter chips.
> But the datasheets of soundcards shows the filters of the 44.1/48 kHz
> sampling rate only (0-20 kHz), as this is the standard where the
> "dB-"measurements are done.
>
> 73 kHz Rx :
> In Europe you can receive the DCF77 signals (77.5 kHz) very well by a
> length of wire (or better a PA0RDT) and directly attaching it to an
> input of a 192 kHz soundcard. (Here 55dB above noise at 600km
> distance, software time-decoding by "SoDiRa" SDR-software). It is the
> same setup as used for SAQ-listening at 17.2 kHz (using HDSDR).
>
> For decoding digimodes (WSPR,JT65,WSQ...) a simple USB-micro-soundcard
> ($5) or onboard is ok, the programs just use "mono" and 48kHz at most,
> even the cheapest (for headset use) do well.
>
> 73 de dg3lv Tobias
>
> Am 15.08.2014 22:12, schrieb [email protected]:
>> Gary,
>>
>> I use a number of expensive and inexpensive external (USB) audio
>> interfaces, and I like them all (good sensitivity, good dynamic
>> range); but I experience the following limitations:
>>
>> A)
>>
>> I have not been able to persuade Windows and/or Speclab to process 24
>> bits (I have been successful in applying 24-bit settings in
>> Windows>ControlPanel>Sound and Speclab, but have not acquired valid
>> data after doing so; and accordingly have always used 16-bit settings
>> with 24-bit external audio interfaces, even though I need at least 24
>> bits for dynamic range considering VLF and LF environmental noise in
>> some of my locations)
>>
>> B)
>>
>> Similarly to the above, I have been able to set up Windows and
>> Speclab for 192kHz sample rates, but have not been able to view past
>> 48kHz without aliasing (and accordingly I settle for 96kHz settings
>> and interfaces in most cases)
>>
>> C)
>>
>> All of my external audio interfaces have steep low-pass filters at or
>> near 22kHz pole frequency, so SNR is compromised for signals at 20kHz
>> and above. I’ve disassembled some of these interfaces in attempts to
>> modify the low-pass filter cutoff frequencies, but without a
>> schematic could not be certain regarding changes.
>>
>> Have you seen any of the above issues with internal or external audio
>> interfaces that you have used?
>>
>> 73, Jim AA5BW
>>
>> *From:*[email protected]
>> [mailto:[email protected]] *On Behalf Of *Gary -
>> G4WGT
>> *Sent:* Friday, August 15, 2014 3:25 PM
>> *To:* [email protected]
>> *Subject:* Re: LF: USB Sound Card?
>>
>> Hi Warren,
>>
>> Yes, I had an internal (on main board) & used it for a while for my
>> grabber when 73kHz was first allocated to USA.
>> It was good to about 94kHz.
>>
>> The SB0490 I suggested is only 96kHz :-((
>>
>> *73, de Gary - G4WGT*
>>
>> * *
>>
>> *MF-LF-VLF Grabber
>> :http://myweb.tiscali.co.uk/wgtaylor/grabber2.html*
>>
>> *Web :http://myweb.tiscali.co.uk/wgtaylor/index.html*
>>
>>
>>
>> .
>>
>> On 15/08/2014 20:09, Warren Ziegler wrote:
>>
>> I guess I should have been more specific .
>>
>> What I am seeking is are some sound cards more stable with respect
>> to sampling rate and calibration? Also, any advantage to 24bit A/D
>> for LF data modes?
>>
>> I wonder if anyone has tried 192kHz sample rate for direct
>> reception of 73kHz?
>>
>> 73 & Tnx Warren
>>
>> On Fri, Aug 15, 2014 at 2:27 PM, Warren Ziegler <[email protected]
>> <mailto:[email protected]>> wrote:
>>
>>
>> I just acquired a Windows Vista tower computer - the price was right
>> it was free!
>>
>> Seems that there is a problem with the internal sound card, but
>> everything else checks out FB.
>>
>> I plan on using it with WSPR and other digital modes, am thinking of
>> an external USB sound card - will any old sound card do ? Or do I
>> need one with a calibrated sampling rate? I suspect that I will need
>> something really good for Spectrum Laboratory if I want to sample at
>> microHertz rates.
>>
>> 73 & Tnx Warren K2ORS
>>
>>
>>
>> --
>> 73 Warren K2ORS
>> WD2XGJ
>> WD2XSH/23
>> WE2XEB/2
>> WE2XGR/1
>>
>
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