external soundcards for digimodes

[Chris Gibson-3]

My own interest in the K3 is principally (but not exclusively) the
digimodes. For that reason I was interested in the suggestion of Simon,
HB9DRV that there might be an operational gain in using a "better" sound
card than that on the PC motherboard. I don't know enough about computing to
make judgements, and it would help me (and others in my position) if more
knowledgeable and experienced folk on the list could offer advice on the
following questions.

Q1.    Does experience suggest that there can be an observable operational
gain in using a sound card different from that built into the PC?

Q2.    Which published technical specifications of a sound card are relevant
to digimode operation?

Q3.    On the basis of the answer to Q2, how does one judge whether one
sound card is "better" than another for digimode operation?

Q4.    Do list members have specific recommendations for cost-effective
external sound cards? (The sound card suggested by Simon costs around as
much in the UK as the 100W upgrade for the basic K3.)

73 Chris, MØPSK
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[Simon (HB9DRV)]

I've tacked answers into your post.

----- Original Message -----
From: "Chris Gibson" <[hidden email]>

Q1.    Does experience suggest that there can be an observable operational
gain in using a sound card different from that built into the PC?

DRV> Depends on built-in card, laptops are usually foul as are soundcards on
the motherboard in general (generalisation).

Q2.    Which published technical specifications of a sound card are relevant
to digimode operation?

DRV> Dynamic range, for example:
http://www.m-audio.com/products/en_us/Delta44-focus.html

Q3.    On the basis of the answer to Q2, how does one judge whether one
sound card is "better" than another for digimode operation?

DRV> Less intermod, less noise, less spurious signals. Less problems due to
strong adjacent signals.

Q4.    Do list members have specific recommendations for cost-effective
external sound cards? (The sound card suggested by Simon costs around as
much in the UK as the 100W upgrade for the basic K3.)

DRV> External is a good idea as you can take it with you and it avoids noise
from the PC. SignaLink USB is good enough, don't know whether there is a K3
cable yet. FWIW the Delta-44 is GBP85 in the UK.

73 Chris, MØPSK

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[Julian, G4ILO]

On 8/16/07, Chris Gibson <[hidden email]> wrote:

[snip]

> Q4.    Do list members have specific recommendations for cost-effective
> external sound cards? (The sound card suggested by Simon costs around as
> much in the UK as the 100W upgrade for the basic K3.)

To be honest, notwithstanding Simon's comments, I'm skeptical of the
benefit of using an external sound card for ordinary data modes. There
are documented benefits for using one for SDR, but that is another
matter. I admit I have never tried using a laptop for radio use, but
the sound card chips on the laptop motherboards seem to be the same as
those used on desktop motherboards so I can't imagine it makes much
difference.

I find I can get pretty good copy of PSK31 (and CW, come to that)
using a Dell Axim PDA running PocketDigi sitting next to the K2 in its
cradle and receiving the audio from the loudspeaker via its built-in
microphone. Obviously, the copy isn't as good as on the PC with a
direct connection. But I think it shows that for modes like that, the
quality of the input really isn't that critical. I've seen greater
differences between different decoding programs. I think MixW is
slightly better than programs that use the PSK Core DLL, for example.

There are arguments for using an external sound card, such as being
able to keep the built-in sound card for other uses. But I wouldn't go
splashing out on an external sound card just on the suggestion that it
might give better results. Chances are, it will make no discernible
difference.
--
Julian, G4ILO K2 s/n: 392  K3 s/n: ???
G4ILO's Shack: www.g4ilo.com
Ham-Directory: www.ham-directory.com
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[Don Wilhelm-4]

Chris,

Typically, the more bits in the Soundcard A-D conversion, the better the
dynamic range.  There is also the noise floor of the soundcard to consider.

Most internal soundcards are 16 bit while the upgrades are typically 24
bits for the A-D.

The Soundblaster Live or Soundblaster Audiogy are good alternatives
IMHO, are available in USB connected external versions as well as
internal cards and will do a good job overall.  They are a bit more
noisy than the Delta-44, but not a pricey.  Depending on your
applications and your OS, there may be some differences in the drivers
available - check the various forums to get a feeling for any
troublespots - the SDR forums are a good resource for that information.

I doubt that you will notice a great difference with the better cards
for most data modes, although your receiving noise floor could be
improved with a good 24 bit card.  If you have interest in Software
Defined Radio, go for the best you can find that fits within your budget.

73,
Don W3FPR

Chris Gibson wrote:
> My own interest in the K3 is principally (but not exclusively) the
> digimodes. For that reason I was interested in the suggestion of Simon,
> HB9DRV that there might be an operational gain in using a "better" sound
> card than that on the PC motherboard. I don't know enough about computing to
> make judgements, and it would help me (and others in my position) if more
> knowledgeable and experienced folk on the list could offer advice on the
> following questions.
>
>  
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[KK7P]

In casual operation, I doubt you'll see much difference. However, if you
are planning on operating during a contest, or otherwise want to use a
wide audio path (SSB bandwidth) with AGC OFF (so strong stations don't
smother weak ones via AGC action) and with lots of signals
simultaneously present, then you'll want a system with very low IMD.

The least expensive soundcard that I own that does a reasonable job with
SDR (and by extension should do a reasonable job under the conditions I
described) is the Creative Soundblaster MP3+.  This is a USB-based
widget, and you can buy these from Creative's online shop, refurbished,
for $14.99.

73,

Lyle KK7P

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[Michael Keane K1MK]

At 09:08 AM 8/16/2007, Don Wilhelm wrote:
>Typically, the more bits in the Soundcard A-D conversion, the better
>the dynamic range.  There is also the noise floor of the soundcard to consider.
>
>Most internal soundcards are 16 bit while the upgrades are typically
>24 bits for the A-D.

Obviously, the performance specs for a 24-bit sound card should be
better than for a 16-bit card.

However, in his review of sound cards for Amateur Radio that appeared
in the May 2007 QST, Jonathan Taylor, K1RFD wrote that very few
digital-mode apps are designed to take advantage of the higher
precision when it is available.

Does anyone know which software apps actually do make use of the
extra bits and the higher performance of a 24-bit sound card?

73,
Mike K1MK

Michael Keane K1MK
[hidden email]

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[Joe Subich, W4TV]

> Obviously, the performance specs for a 24-bit sound card should be
> better than for a 16-bit card.
>
> Does anyone know which software apps actually do make use of the
> extra bits and the higher performance of a 24-bit sound card?

There is not much that can be done in the application to take
advantage of the 24 bit sound cards.  All of the devices are
limited on the "strong signal" end of the spectrum by their power
supply (typically 5 volt) which limits the signal to the ADC to
about 4.5 volts p-p.  On the low signal end, the digital software
is limited by the noise level from a "quiet band" (receiver IF
noise, atmospheric noise, etc.) at the receiver output.  From memory,  
most receivers I've seen show composite noise floors about 80 dB
below their peak output (peak output is generally around 200 mV
average or somewhat less than 1 volt p-p) with no antenna and
"quiet band" noise around 70 dB below maximum output.

Even if the DSP algorithms in the digital software could get 10
dB below the noise, the 16 bit sound cards with their 95 to 97
dB theoretical dynamic range would be more than enough for most
amateur work at HF.  

They key to getting everything you can with soundcard modes on
HF is having a very low noise audio amplifier between the
receiver and ADC (it may be in the soundcard) and minimizing
any power supply and logic noise in the sound card.  If you
will be using AGC and narrow filters in the receiver (one
key to maximum weak signal effectiveness), the receiver AGC will
limit the dynamic range into the sound card to well less than
40 dB (the difference between MDS and AGC threshold) in any case.

You want the peak audio to be as close to the 4 V p-p point
as possible to make maximum use of the sound card's available
dynamic range as you can.  If the maximum signal to the ADC is
only one volt p-p you have already given away 12 dB of DR!

73,

   ... Joe, W4TV
   

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of
> Michael Keane K1MK
> Sent: Thursday, August 16, 2007 11:49 AM
> To: Elecraft Reflector
> Subject: Re: [Elecraft] external soundcards for digimodes
>
>
> At 09:08 AM 8/16/2007, Don Wilhelm wrote:
> >Typically, the more bits in the Soundcard A-D conversion, the better
> >the dynamic range.  There is also the noise floor of the
> soundcard to consider.
> >
> >Most internal soundcards are 16 bit while the upgrades are typically
> >24 bits for the A-D.
>
> Obviously, the performance specs for a 24-bit sound card should be
> better than for a 16-bit card.
>
> However, in his review of sound cards for Amateur Radio that appeared
> in the May 2007 QST, Jonathan Taylor, K1RFD wrote that very few
> digital-mode apps are designed to take advantage of the higher
> precision when it is available.
>
> Does anyone know which software apps actually do make use of the
> extra bits and the higher performance of a 24-bit sound card?
>
> 73,
> Mike K1MK
>
> Michael Keane K1MK
> [hidden email]
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
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>
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>
>

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[David Cutter]

The SSM2165 is a good speech compressor and not expensive.  I'm assuming it
will work on data....?  to bring up the level as required.

You can get a complete kit from www.box73.com DYC-817   (Code 734980)
External dynamic compressor kit for FT-817.

Or from OK1CDJ, but I can't find the link at the moment.

This will incur some extra noise, but there are components to adjust to
optimise compression etc.

David
G3UNA


----- Original Message -----
From: "Joe Subich, W4TV" <[hidden email]>
To: "'Michael Keane K1MK'" <[hidden email]>; "'Elecraft Reflector'"
<[hidden email]>
Sent: Thursday, August 16, 2007 5:50 PM
Subject: RE: [Elecraft] external soundcards for digimodes

>
>> Obviously, the performance specs for a 24-bit sound card should be
>> better than for a 16-bit card.
>>
>> Does anyone know which software apps actually do make use of the
>> extra bits and the higher performance of a 24-bit sound card?
>
> There is not much that can be done in the application to take
> advantage of the 24 bit sound cards.  All of the devices are
> limited on the "strong signal" end of the spectrum by their power
> supply (typically 5 volt) which limits the signal to the ADC to
> about 4.5 volts p-p.  On the low signal end, the digital software
> is limited by the noise level from a "quiet band" (receiver IF
> noise, atmospheric noise, etc.) at the receiver output.  From memory,
> most receivers I've seen show composite noise floors about 80 dB
> below their peak output (peak output is generally around 200 mV
> average or somewhat less than 1 volt p-p) with no antenna and
> "quiet band" noise around 70 dB below maximum output.
>
> Even if the DSP algorithms in the digital software could get 10
> dB below the noise, the 16 bit sound cards with their 95 to 97
> dB theoretical dynamic range would be more than enough for most
> amateur work at HF.
>
> They key to getting everything you can with soundcard modes on
> HF is having a very low noise audio amplifier between the
> receiver and ADC (it may be in the soundcard) and minimizing
> any power supply and logic noise in the sound card.  If you
> will be using AGC and narrow filters in the receiver (one
> key to maximum weak signal effectiveness), the receiver AGC will
> limit the dynamic range into the sound card to well less than
> 40 dB (the difference between MDS and AGC threshold) in any case.
>
> You want the peak audio to be as close to the 4 V p-p point
> as possible to make maximum use of the sound card's available
> dynamic range as you can.  If the maximum signal to the ADC is
> only one volt p-p you have already given away 12 dB of DR!
>
> 73,
>
>   ... Joe, W4TV
>
>
>
>> -----Original Message-----
>> From: [hidden email]
>> [mailto:[hidden email]] On Behalf Of
>> Michael Keane K1MK
>> Sent: Thursday, August 16, 2007 11:49 AM
>> To: Elecraft Reflector
>> Subject: Re: [Elecraft] external soundcards for digimodes
>>
>>
>> At 09:08 AM 8/16/2007, Don Wilhelm wrote:
>> >Typically, the more bits in the Soundcard A-D conversion, the better
>> >the dynamic range.  There is also the noise floor of the
>> soundcard to consider.
>> >
>> >Most internal soundcards are 16 bit while the upgrades are typically
>> >24 bits for the A-D.
>>
>> Obviously, the performance specs for a 24-bit sound card should be
>> better than for a 16-bit card.
>>
>> However, in his review of sound cards for Amateur Radio that appeared
>> in the May 2007 QST, Jonathan Taylor, K1RFD wrote that very few
>> digital-mode apps are designed to take advantage of the higher
>> precision when it is available.
>>
>> Does anyone know which software apps actually do make use of the
>> extra bits and the higher performance of a 24-bit sound card?
>>
>> 73,
>> Mike K1MK
>>
>> Michael Keane K1MK
>> [hidden email]
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>  http://mailman.qth.net/mailman/listinfo/elecraft
>>
>> Help: http://mailman.qth.net/subscribers.htm
>> Elecraft web page: http://www.elecraft.com
>>
>>
>
> _______________________________________________
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[Richard Kent]

Chris,
        Built on the motherboard type sound cards need to be checked before
using them for more than just listening. Many, but not all, are designed to
provide signals for "cheap computer" type speakers. This means that the
audio bandpass is pre-distorted to "match" these speakers. Often this means
a boosted bass and sometimes boosted treble. All Windows versions have some
control of this depending on the driver in use. However, sometimes this is
designed into the chipset and changing it in Windows makes it worse.
        The other problem I have had is excessive noise. Power supply, chip
noise you name it. One that I measured barely made -40db noise floor. This
may not sound so bad, broadcasters are to make -60 min. for the entire
system. In this case the card is too noisy adding it to a system makes the
noise worse.
        Many third party "audiophile" type sound cards both internal and
external have flat response and noise floor well beyond -60db. Most have
better bypassing and dynamic range. Another difference could be that these
cards often sample out to 96K and some even higher sample rates, a benefit
if experimenting with SDR. Your software may not use the extra resolution or
the sample rate, but a card capable of better will generally do better even
in the lesser mode.

Good Luck
Richard Kent

My own interest in the K3 is principally (but not exclusively) the
digimodes. For that reason I was interested in the suggestion of Simon,
HB9DRV that there might be an operational gain in using a "better" sound
card than that on the PC motherboard. I don't know enough about computing to
make judgements, and it would help me (and others in my position) if more
knowledgeable and experienced folk on the list could offer advice on the
following questions.

Q1.    Does experience suggest that there can be an observable operational
gain in using a sound card different from that built into the PC?

Q2.    Which published technical specifications of a sound card are relevant
to digimode operation?

Q3.    On the basis of the answer to Q2, how does one judge whether one
sound card is "better" than another for digimode operation?

Q4.    Do list members have specific recommendations for cost-effective
external sound cards? (The sound card suggested by Simon costs around as
much in the UK as the 100W upgrade for the basic K3.)

73 Chris, MØPSK

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[Bill Steffey NY9H]

At 12:19 PM 8/16/2007, David Cutter wrote:
>The SSM2165 is a good speech compressor and not expensive.  I'm
>assuming it will work on data....?  to bring up the level as required.

wonder if the control of the existing SSM2165 on the K2's ssb board
is adequate to optimize the data....????

bill

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[Joe Subich, W4TV]

> The SSM2165 is a good speech compressor and not expensive.  
> I'm assuming it will work on data....?  to bring up the level
> as required.

You don't want compression on data modes.  Better to use a good
low noise, single rail op amp with a low noise reference as a
preamplifier to bring the maximum receive level up to 4 V P-P.
Compression effects the characteristics of some data modulation
modes (one reason for the suggestions to not run any transmit
ALC with data modes other than FSK).

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of David Cutter
> Sent: Thursday, August 16, 2007 1:19 PM
> To: Joe Subich, W4TV; 'Michael Keane K1MK'; 'Elecraft Reflector'
> Subject: Re: [Elecraft] external soundcards for digimodes
>
>
> The SSM2165 is a good speech compressor and not expensive.  
> I'm assuming it
> will work on data....?  to bring up the level as required.
>
> You can get a complete kit from www.box73.com DYC-817   (Code 734980)
> External dynamic compressor kit for FT-817.
>
> Or from OK1CDJ, but I can't find the link at the moment.
>
> This will incur some extra noise, but there are components to
> adjust to
> optimise compression etc.
>
> David
> G3UNA
>
>
> ----- Original Message -----
> From: "Joe Subich, W4TV" <[hidden email]>
> To: "'Michael Keane K1MK'" <[hidden email]>; "'Elecraft
> Reflector'"
> <[hidden email]>
> Sent: Thursday, August 16, 2007 5:50 PM
> Subject: RE: [Elecraft] external soundcards for digimodes
>
>
> >
> >> Obviously, the performance specs for a 24-bit sound card should be
> >> better than for a 16-bit card.
> >>
> >> Does anyone know which software apps actually do make use of the
> >> extra bits and the higher performance of a 24-bit sound card?
> >
> > There is not much that can be done in the application to take
> > advantage of the 24 bit sound cards.  All of the devices are
> > limited on the "strong signal" end of the spectrum by their power
> > supply (typically 5 volt) which limits the signal to the ADC to
> > about 4.5 volts p-p.  On the low signal end, the digital software
> > is limited by the noise level from a "quiet band" (receiver IF
> > noise, atmospheric noise, etc.) at the receiver output.  
> From memory,
> > most receivers I've seen show composite noise floors about 80 dB
> > below their peak output (peak output is generally around 200 mV
> > average or somewhat less than 1 volt p-p) with no antenna and
> > "quiet band" noise around 70 dB below maximum output.
> >
> > Even if the DSP algorithms in the digital software could get 10
> > dB below the noise, the 16 bit sound cards with their 95 to 97
> > dB theoretical dynamic range would be more than enough for most
> > amateur work at HF.
> >
> > They key to getting everything you can with soundcard modes on
> > HF is having a very low noise audio amplifier between the
> > receiver and ADC (it may be in the soundcard) and minimizing
> > any power supply and logic noise in the sound card.  If you
> > will be using AGC and narrow filters in the receiver (one
> > key to maximum weak signal effectiveness), the receiver AGC will
> > limit the dynamic range into the sound card to well less than
> > 40 dB (the difference between MDS and AGC threshold) in any case.
> >
> > You want the peak audio to be as close to the 4 V p-p point
> > as possible to make maximum use of the sound card's available
> > dynamic range as you can.  If the maximum signal to the ADC is
> > only one volt p-p you have already given away 12 dB of DR!
> >
> > 73,
> >
> >   ... Joe, W4TV
> >
> >
> >
> >> -----Original Message-----
> >> From: [hidden email]
> >> [mailto:[hidden email]] On Behalf Of
> >> Michael Keane K1MK
> >> Sent: Thursday, August 16, 2007 11:49 AM
> >> To: Elecraft Reflector
> >> Subject: Re: [Elecraft] external soundcards for digimodes
> >>
> >>
> >> At 09:08 AM 8/16/2007, Don Wilhelm wrote:
> >> >Typically, the more bits in the Soundcard A-D conversion,
> the better
> >> >the dynamic range.  There is also the noise floor of the
> >> soundcard to consider.
> >> >
> >> >Most internal soundcards are 16 bit while the upgrades
> are typically
> >> >24 bits for the A-D.
> >>
> >> Obviously, the performance specs for a 24-bit sound card should be
> >> better than for a 16-bit card.
> >>
> >> However, in his review of sound cards for Amateur Radio
> that appeared
> >> in the May 2007 QST, Jonathan Taylor, K1RFD wrote that very few
> >> digital-mode apps are designed to take advantage of the higher
> >> precision when it is available.
> >>
> >> Does anyone know which software apps actually do make use of the
> >> extra bits and the higher performance of a 24-bit sound card?
> >>
> >> 73,
> >> Mike K1MK
> >>
> >> Michael Keane K1MK
> >> [hidden email]
> >>
> >> _______________________________________________
> >> Elecraft mailing list
> >> Post to: [hidden email]
> >> You must be a subscriber to post to the list.
> >> Subscriber Info (Addr. Change, sub, unsub etc.):
> >>  http://mailman.qth.net/mailman/listinfo/elecraft
> >>
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> >> Elecraft web page: http://www.elecraft.com
> >>
> >>
> >
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>

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