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Date: Wed, 8 Feb 2012 19:39:57 +0000
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From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: QRSS3 "challenge" results
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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 <james.moritz@btopenworld.com> 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? =A0With 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 po=
wer
> from a given transmitter, compared to Opera. I suppose it depends whether
> you are more worried about corona on the antenna, or your electricity bil=
l
> ;-)
>
> 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 =A0between "good" and "average". Surely any lowe=
r
> 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, =A0and 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 =A0G4JNT
>
>
> On 8 February 2012 16:00, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> 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: rsgb_lf_group@blacksheep.org
>> 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 resul=
ts
>> (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
>
>
>
>
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