73

On 16/08/14 01:32, [email protected] wrote:

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

--
de Pat G4GVW
QTH Nr Felixstowe, Suffolk
East coast of UK