[Moon] QRA64 false decodes

[Zdenek SAMEK-OK1DFC]

Just only comment of false decoding due to EA9LZ operating.
Even I had big pile up, I was decoding properly all stations, and always the
strongest was decoded. Same situation on 6 and 3cm. I will have on my web, 
decoded files to public check if anybody will be interesting.
>From this traffic only one recommendation for QRA64D using. 
After CQ of DX station, everybody on band can call him even CFOM. Only if 
you see, that DX is answering to let say G3WDG, stop to call DX, because due
to not proper pointing to the Moon can be change strongest of signal and DX 
will decode different station as is calling. So if all stations will stop 
and wait to next CQ of DX, all goes well and not any problem was recognize 
during all time.
p.s. back at home after two day driving yesterday around 22"00 local time, 
see you from next expedition in 2018!


-- 
Zdenek - OK1DFC
www.ok1dfc.com
QRV EME 144 MHz - 10 GHz
WAC 432 - 1296 - 2320 MHz
WAZ #9 - WAS 432 #29
DXCC 432 - 1296 MHz

---------- Původní e-mail ----------
Od: G3WDG via Moon <moon at moonbounce.info>
Komu: Peter Sundberg <sm2cew at telia.com>
Datum: 13. 10. 2017 14:40:54
Předmět: Re: [Moon] QRA64 false decodes 
"Hi Peter 

Yes, QRA64 is not completely immune from false decodes - we saw one or two 
while doing the simulation work that went into the Dubus 3/17 article and 
I have seen one or two while monitoring band noise for long periods. Joe 
can probably explain this better, but there is always a finite chance of 
the decoder reaching a false solution when the signal to noise ratio is 
low. 

The developers put in a significant amount of work went to reduce false 
decodes to a level where they very uncommon. 

Also, and quite importantly on the rare occasions where you do see one, 
our experience is that they are clearly obvious as false, like in your 
example where the callsign and locator make no sense. 

Both on the air and in the simulations (which involved many thousands of 
files) we have never seen a false decode that could have confused or 
invalidated a QSO, such as printing a wrong callsign or incorrect report. 
Because of this (and its superior decoding of very weak signals) QRA64 has 
an advantage over other 'slow' modes, when employing correlation decoding 
to improve sensitivity. 


73 

Charlie 





> Hi Charlie, 
> 
> This was a QRA64 decode today of the DL0SHF 10 GHz EME beacon, 
> apparently there are false decodes in QRA64 also under certain 
> circumstances: 
> 
> 1144 -22 2.5 1144 :* CQ AR8NDK JB02 
> 
> Normally decodes look like this 
> 
> 0820 -11 2.5 639 :* CQ DL0SHF JO54 
> 
> I often monitor Per DK7LJ's superb 10G EME beacon for extended 
> periods to get a feeling for the different limitations of my EME 
> window with my small dish. Limitations are mainly based on blockage 
> from different towers on my property. And I must admit that the false 
> decode above was quite surprising and highly unusual. 
> 
> 73 
> Peter SM2CEW 
> 
> 
> 
> At 10:46 2017-10-10, G3WDG via Moon wrote: 
> 
> snip.. 
> 
>>With QRA64 it is our 100% experience 
>>that you can rely on a decode being correct. 
>> 
>>73 
>> 
>>Charlie 
> 
> 
> 


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