On 8/19/2012 11:40 PM, Bill Frantz wrote:
> The other reason I might want an external interface is to have a
> larger dynamic range into the computer. Most computers have a 16
> bit A/D. With a 24 bit A/D you will have less trouble with
> strong signals causing overload when trying to receive weak signals.
With real receivers you probably will never notice the difference in
dynamic range between a 16 and 24 bit sound card. The receiver AGC
- even only modest AGC - will keep the dynamic range presented to the
sound card well within anything the 16 bit sound card can handle.
That is *unless* the 16 bit card is poorly designed with internal
noise that wastes a significant part of the 16 bit range.
Even without AGC, the range between "background noise" (the noise
floor of the demodulation process including sky noise, thermal
noise in the IF, etc.) and the clipping point of the audio output
can be considerably less than 90 dB in "real" receivers. Audio
output levels tend to range from around 10 mV with "no signal" to
just under 5V P-P (2V RMS) at best ... that's less than 50 dB.
Even if one assumes the software can decode a 1 mV signal in the
10 mV nose floor, the resulting dynamic range is still much less
than 90 dB provided by a properly designed 16 bit sound card and
unless the 24 bit soundcard uses other than the typical 5V power
supply, its real performance will be limited by the same 5V P-P
audio levels!
Taken a step further - if the receiver produces a 1 mV noise floor
with 24V P-P output (+/- 12V supplies), that's *still* less than
90 dB of range.
73,
... Joe, W4TV
On 8/19/2012 11:40 PM, Bill Frantz wrote:
> The other reason I might want an external interface is to have a
> larger dynamic range into the computer. Most computers have a 16
> bit A/D. With a 24 bit A/D you will have less trouble with
> strong signals causing overload when trying to receive weak signals.
>
> IMHO, using the computer audio I/O is a nice way to get your
> feet wet in digital modes. However it is like a beginning rig --
> limited in performance. People who opt for an Elecraft class
> radio probably will want something better.
>
> Cheers - Bill, AE6JV
>
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