was. I've noticed that, unless there's QRM, reducing the receiver
bandwidth really doesn't help, so the limit factor is the "processing".
the processing just can't make the effective bandwidth any lower.
brains can't. It would be interesting to compare the performance at 15 wpm.
> On 2019-05-19 9:50 AM, Wes wrote:
>> FT8 reports negative SNRs number but we both know those are bogus.
>
> All of the modes that quote negative SNRs are doing so by using SNR
> in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth
> (bandwidth of the final filter whether than be a narrow IF filter,
> the "ear-brain" filter or a software [computation] filter).
>
> If one looks at the SNR thresholds of the various Joe Taylor "slow"
> modes, 80% of the "negative" SNR can be attributed entirely to the
> difference between the occupied bandwidth and the [excess] measurement
> bandwidth. The remainder can be attributed to software processing
> algorithms that take advantage of the fact that noise is random while
> the signal is not - in essence reporting using a "peak noise" level
> while actually decoding against a "minimum noise" level (like copying
> CW through static crashes - one looses a dit/dah during the crash but
> fills that in from the context).
>
> 73,
>
> ... Joe, W4TV
>
>
> On 2019-05-19 9:50 AM, Wes wrote:
>> I feel like I'm gonna be slappin' a tar baby by responding.
>>
>> Since we are discussion HF radios, I was assuming HF. I realize
>> JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly
>> random. If your computer clock is off, sorry, no QSO. FT8 reports
>> negative SNRs number but we both know those are bogus.
>>
>> Wes N7WS
>>
>>
>> On 5/19/2019 5:58 AM, Ed W0YK wrote:
>>> JT65, JT9, FT8.
>>>
>>> 73,
>>> Ed W0YK
>>>
>>> -------- Original message --------
>>> From: Wes <
[hidden email]>
>>> Date: 5/19/19 07:49 (GMT-06:00)
>>> To:
[hidden email]
>>> Subject: Re: [Elecraft] Sensitivity - Was K4 Observations
>>>
>>> What current modes hear below the noise level?
>>>
>>> Wes N7WS