RE: [wsjtgroup] Do you think a sound card interface can make a difference?
- If you're interested in an interface at a much
lower price (and without an external sound card),
you may want to check out the MicroHam Keyer -
much like the Rig Expert, and works well. The
company provides exceptional customer support,
and provides free firmware/software updates regularly.
Yes, it's the computer program that does the
decoding, not "the box". Purportedly, the
external sound card "helps" by providing a less
noisy signal to work with. I've been using the
MicroHam Keyer for WSJT and it does an excellent
job, along with all the other digital modes. It
also features the WinKey CW chip, and lets you
use only USB connections - no serial port issues.
No financial interest, just a satisfied customer.
- "Russ K2TXB" <k2txb@...> writes:
> Does RigExpert provide an interface via the USB connection that looksYes.
> like a normal sound card, so that WSJT can interface?
> Other that that, it looks like a nice product, but OH the price!Yes, they are pricey. How much would you pay for an antenna that gave you
10 db better S/N?
> Also, I suspect that many high end sound cards will be just as quiet.The person who tested it (an EE with real test equipment, not me) stated that
> And finally, it still does not appear that RigExpert can decode anything.
> However it appears, Bob, that what you mean is that signals through the rig
> expert can be decoded when they are 10 db weaker than via other interfaces
> you have tested.
the RigExpert sound card codec (ADC) provides 10 db better S/N. That means
that under 'no signal' conditions, the noise floor of the sound card is 10 db
lower than the other tested cards.
I'd be very interested in any comments from Joe, K1JT, on these figures.
Bob Poortinga K9SQL
Bloomington, Indiana US
- Bob --
> RigExpert is not a program but it is more than an interface box. ItWhen something sounds too good to be true, it usually is.
> contains both an interface AND an external sound card. It is this
> external sound card that provides a 10db S/N improvement over internal
> sound cards.
Specifications of sound cards that refer to the "S/N" of the card are
completely irrelevant to use of the card with WSJT -- or indeed just
about any other ham radio software. The reason is that the
signal-to-noise ratio that matters for MS or EME (with WSJT), or for HF
use of PSK31, is determined far upstream of the device interfacing your
radio to your computer.
A sound card would have to be EXTREMELY poor -- so poor that it would be
unacceptable for "normal" computer uses such as recording/playing music,
etc. -- before its S/N rating would significantly degrade the decoding
ability of WSJT and similar programs.
The noise that the WSJT decoders must cope with is a combination of
cosmic noise, atmospheric noise, and receiver noise; sound card noise is
many tens of dBs weaker, and entirely negligible.
As it happens, there is one way in which poor sound cards can adversely
affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
rate. WSJT uses a sample rate of 11025 Hz for both input and output.
All sound cards claim to support this rate, but some do it by
interpolating rather poorly from another sampling rate.
The Rig Expert may be a convenient way to do your radio-computer
interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
weak meteor pings or EME signals.
-- 73, Joe, K1JT
- Joe Taylor K1JT <joe@...> writes:
> As it happens, there is one way in which poor sound cards can adverselyDoesn't sampling jitter also introduce noise? Wouldn't a highly-stable
> affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
sampling clock produce a lower noise floor resulting in better decodes?
> The Rig Expert may be a convenient way to do your radio-computerThanks, Joe, I was simply looking for a definitive answer in response to
> interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
> weak meteor pings or EME signals.
the claims of others.
Bob Poortinga K9SQL
Bloomington, Indiana US
- Bob Poortinga wrote:
> Joe Taylor K1JT <joe@...> writes:Yes, but for any plausible amount of jitter that noise will cause
>>As it happens, there is one way in which poor sound cards can adversely
>>affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
> Doesn't sampling jitter also introduce noise? Wouldn't a highly-stable
> sampling clock produce a lower noise floor resulting in better decodes?
negligible degradation of the WSJT audio signals sent from your radio to
the sound card input.
The "inaccuracies in sampling rate" that I mentioned are not jitter, but
rather a sampling rate that is constant but offset from the nominal
value by a significant amount. WSJT always requests a sampling rate of
11025 samples per second. The actual sample rate can be somewhat
different. Some recent sound cards are "off" by as much as 75 Hz,
sampling at about 11100 Hz instead of 11025. If uncorrected, this means
that the WSJT tone spacing will be off by about 0.7% in both time and
frequency, causing a loss of sensitivity up to about 2 dB.
The next WSJT version to be released will have the ability to correct
for errors in sound card sample rates.
>>The Rig Expert may be a convenient way to do your radio-computerHappy to help!
>>interfacing, but it will NOT gain you 10 dB (or even 1 dB) in detecting
>>weak meteor pings or EME signals.
> Thanks, Joe, I was simply looking for a definitive answer in response to
> the claims of others.
> 73 de Bob, K9SQL
-- 73, Joe, K1JT
- Hi Joe
Do you have any examples so we know which sound cards to avoid? For
example at the moment I'm using a cheap OEM PCI soundcard. I also have
an external Soundblaster USB card so I wonder if there would be a real
advantage in using that instead?
PS the facility to click on and decode pings & bursts in real time in
5.8.6 is wonderful!
Bob Poortinga wrote:
> Joe Taylor K1JT <joe@...> writes:
> > As it happens, there is one way in which poor sound cards can adversely
> > affect WSJT signals. It's not S/N, but rather inaccuracies in sampling
> > rate.