On Sat, 30 Jan 1999 01:47:27 GMT wrt@eskimo.com (Bill Turner, W7TI)
writes:
>
>On Fri, 29 Jan 1999 19:23:17 -0600, Jon Ogden <jono@enteract.com>
>wrote:
><snip>
>>>If you send dit-dit-dit-dah and noise or QRM causes you to
>>>miss a dit and copy it as U instead of V, you have no way of knowing
>>>you got it wrong.
>>
>>Yes, I do. Let's say the V was the start of the word Very. When I
>hear
>>Uery, I know that I got it wrong. I have error correction.
>
>Ok, if you're happy with "uery", no problem. I'm not.
In the real world its called "fill" by experienced ops. Of course its not
applicable to copying code groups ( :
________________
>Yes, it CAN work magic. It's done with signal averaging. The DSP
>will record a short piece of signal, say a few hundred milliseconds,
>and analyze it looking for a pattern buried in the noise. The pattern
>of course, is the tone from the signal you're trying to receive. In
>effect it "subtracts" the totally random stuff from the non-random
>stuff and what's left is the signal. If you ever get a chance, watch
>a modern digital storage oscilloscope in action. Put in a sine wave
>which is totally buried in noise. In the "normal" mode, nothing is
>visible to the eye except what appears to be white noise. Turn on the
>"averaging" mode and like magic, the noise fades away and the sine
>wave appears. The first time you see this happen it will give you
>goose bumps. At least it did me.
It sure looks good on a lab scope and there are $10K + boxes that are
available but IMO the ham related stuff is mostly useless with a GOOD
radio.
I have bought and sold just about every ham style DSP unit on the market
during attempts to improve 160M DX and VHF meteor scatter results. The
only item I still have is one of the first DSP on the market, an old JPS
NF-60 automatic notch filter which far outperforms the multiple use boxes
for notching out carriers for those rare times I go on SSB.
Under the best of condx, the NF-60 was used in series with other DSP
units but outside of a lab I found that having only 2 hands really
limited the usefulness. Drift and tune forever which is why many EME ops,
etc choose the DSP between their ears.
73 Carl KM1H
.
>
>This same technology can be applied to radio. NASA has used it for
>years to dig spacecraft signals out of the noise. It works; now we
>need it applied to amateur radio. It's coming.
>
>
>73, Bill W7TI
>
>
>--
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>Problems: owner-amps@contesting.com
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>
>
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