...of course -
thinking this through further...
QRSS is also about 50% duty cycle, so if we insist on the mean power
rule for Opera, it has to apply to QRSS as well.
So leave the QRSS and Op curves where they are, and move WSPR 3dB to the left.
Which means WSPR now crosses the QRSS curves at a point corresponding
to a significant proportion of failed characters.
This is exactly what you might expect when comparing a heavy error
corrected code against one carrying no correction. The former is all
or nothing, the latter ends up, well, ...just dubious.
It would be interesting to now do the same comparison with DFCW, and
DFCWi which are closer to 100% duty cycle modes and have a sort-of
mental soft error correction added. But of course, we have now gone
away from simple on-off.
Andy G4JNT
On 8 February 2012 19:39, Andy Talbot <[email protected]> wrote:
> Communications theory doesn't care if your transmitter can deliver
> more power. It only takes into account the actual power is does
> transmit
>
> If you are limited by PA power output capability, then at OP2 / WSPR
> speeds, you'll have to accept you will win 3dB using WSPR
>
> Think of it in electricity bill terms rather than in PA capability.
>
> Andy
>
>
> On 8 February 2012 18:32, James Moritz <[email protected]> wrote:
>> Dear Andy, Rik, LF Group,
>>
>>
>> G4JNT wrote:
>> ...>When you generasted the Opera and WSPR audio files, did you take into
>> account that Opera should be compared using the mean power? With its
>> 50% duty cycle, this means an Opera Tx has to have twice the power
>> rating of one running WSPR for equal S/N ratios...>
>>
>> ... But on the other hand, you could argue that since the TX power is in
>> practice normally limited by the PEP available from the PA. So by having
>> 100% duty cycle, WSPR effectively doubles the available average output power
>> from a given transmitter, compared to Opera. I suppose it depends whether
>> you are more worried about corona on the antenna, or your electricity bill
>> ;-)
>>
>> I think it is interesting that there is only a small difference between
>> "average" and "top 10" operators - down to about 70% correct copy, there
>> appears be less than 1dB between "good" and "average". Surely any lower
>> levels of accuracy would be pretty useless for communicating information,
>> even in an amateur context. This suggests the "human factor" in QRSS
>> reception is perhaps quite a small factor.
>>
>> Cheers, Jim Moritz
>> 73 de M0BMU
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> If you used peak power (ie. the same transmitter amplitude), the curve
>> plotted for Opera will have to move 3dB to the right, making it more
>> comparable with WSPR - and then more as one would expect.
>>
>> Given the similarity of the error correction overhead for Opera and
>> WSPR, and nearly matching symbol rate for OP2 ,and that OOK and FSK
>> have comparable error rates for the same mean power, suggests the two
>> modes should give roughly similar performance.
>>
>> Only 27 responses, that doesn't seem very many compared with the
>> numbers that monitor this reflector.
>>
>> Andy G4JNT
>>
>>
>> On 8 February 2012 16:00, Rik Strobbe <[email protected]> wrote:
>>>
>>> Dear all,
>>>
>>> the results of the "QRSS3 challenge" can be found at
>>> http://on7yd.strobbe.eu/QRSS/
>>> Hit refresh if you still see the old challenge.
>>>
>>> Thanks to all who participated !
>>>
>>> 73, Rik ON7YD - OR7T
>>>
>>> ________________________________
>>> Van: Rik Strobbe
>>> Verzonden: donderdag 2 februari 2012 18:17
>>> Aan: [email protected]
>>> Onderwerp: QRSS3 "challenge"
>>>
>>> Dear all,
>>>
>>>
>>>
>>> as mentioned some days ago I generated a whole series of Opera, WSPR
>>> and QRSS3 audio with a known SNR.
>>>
>>> For Opera and WSPR it was easy to determine the lowest SNR for a proper
>>> decode. But for QRSS3 it is much more difficult as it depends on the
>>> operators "sharp eye". It must be somewhere in the range of -24 to -28dB
>>> SNR
>>> (@ 2.5kHz BW).
>>>
>>> Today I did put all the QRSS3 screenshots in this range in a
>>> website, where you can fill in what you see (decode) for each screenshot.
>>>
>>> I would like to invite all of you to give it a try and send me the results
>>> (the more entries the better the statistics).
>>>
>>> After some time (Feb 10th) will put all results into some nice tables
>>> and graphs and make them available.
>>>
>>> Of course no personal (individual) results will be published. But based on
>>> the results every participant (who keeps his results) can see where he
>>> ends.
>>>
>>>
>>>
>>> The "QRSS3 Challenge" can be found at http://on7yd.strobbe.eu/QRSS/
>>>
>>>
>>>
>>> 73, Rik ON7YD - OR7T
>>
>>
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 2012.0.1913 / Virus Database: 2112/4795 - Release Date: 02/07/12
>>
>>
>>
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