Message-ID: <6FC7B34C47134A0A86C1641F2A3F4489@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <CAMFjj73P4GEnkpJjQ1LLHBsY3zpbRSCn+FQBXVKeDye2UerPbA@mail.gmail.com> <CAMFjj71p3xTzFoa_aYrYmYD-=jxAD=VKg2-VHYLovS2iyRPsRg@mail.gmail.com> <53EE5E74.4030405@tiscali.co.uk> <02fc01cfb8c5$542235f0$fc66a1d0$@comcast.net> <53EE894B.8050502@gmx.net>
In-Reply-To: <53EE894B.8050502@gmx.net>
Date: Sat, 16 Aug 2014 00:48:35 +0100
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Subject: Re: LF: USB Sound Card?
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Status: O

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" <DG3LV@gmx.net>
Sent: Friday, August 15, 2014 11:27 PM
To: <rsgb_lf_group@blacksheep.org>
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 hvanesce@comcast.net:
>> 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:*owner-rsgb_lf_group@blacksheep.org
>> [mailto:owner-rsgb_lf_group@blacksheep.org] *On Behalf Of *Gary - G4WGT
>> *Sent:* Friday, August 15, 2014 3:25 PM
>> *To:* rsgb_lf_group@blacksheep.org
>> *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 <wd2xgj@gmail.com
>>     <mailto:wd2xgj@gmail.com>> 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
>>
>