> Many hardware and software decoders are cheap enough to warrant
> running in parallel on the same signal which provides the strengths
> of each, as conditions vary.
There is one caveat when running multiple decoders on a single receiver
- be certain to do it in such a way as the receive signal (audio) is
distributed equally to all decoders - including the soundcard. It is
very easy to find that one device has a lower input impedance than
others and "hogs" the audio ... or that one device requires a lot
less drive than others and overdrives easily.
A less obvious problem that can "color" any comparison is operating
the devices at a "compromise" audio level that fails to make effective
use of each decoder's dynamic range. With a compromise input level,
some devices may be driven into distortion prior to the A/D converter
while others may be operating in an area of low A/D resolution.
An audio distribution amplifier with individual level controls for
each output is almost mandatory unless all devices have individual
preamplifiers and their own (hardware) input level control. The
input level (drive) to each device should be adjusted so that the
maximum signal level is slightly (6 to 10 dB) below the input clipping
point to make the best use of each device's dynamic range.
73,
... Joe, W4TV
On 8/31/2010 5:29 PM, Ed Muns wrote:
> Dick, K7VC, wrote:
>> I would like to thank everyone for their inputs on the best
>> hardware RTTY decoder.
>>
>> As good as these units are, I have detected what seems to be
>> an undercurrent of opinion that even the best are still using
>> decade-old technology and the best modern software solutions
>> are surpassing the best hardware solutions. Am I reading this right?
>
> Depending on how you define "best", this conclusion will be correct or not.
> RITTY is decade-old software technology that is superior to most other
> software and hardware decoders in some signal detection scenarios. What is
> important to you?
>
> * only weak signal detection
> * realistically available decoders
> * non-zero-beat signals
> * signals buried in QRN
> * pile-ups
> * nearby loud signals
> * multipath
> * flutter
> * all conditions with equal probability
> * etc.
>
> Many hardware and software decoders are cheap enough to warrant running in
> parallel on the same signal which provides the strengths of each, as
> conditions vary.
>
> Ed - W0YK
>
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