Re: [CQ-Contest] Understanding the dynamic error free RBN algorithm

[Brett Graham <vr2bg@harts.org.hk>]

DJ7WW added:

> Very true and a contester already adressed a contest sponsor and 
> insisted on
> disqualification of his competitor (ahead of him of course), whos harmonic
> was shown on a different band in RBN.
>
> 73
> Peter
>
> -----Original Message-----
>
> S56A4ZR said:
>
> > > Real life 0IF RX could achieve 60 dB unavoidable image rejection and
> > > this is not enough in contests. Our ham freqs are NOT channelized
> > > although one knows where the image is!
> The most popular version of QSD receiver has EVEN HIGHER response at
> harmonics of its LO than -60 dBc
Though it should be noted that the LO spurious response of QSD receivers 
does not appear on multiples of the frequency the signal is really on.
Direct sampling SDRs can have a spurious response that will appear on 
multiples of the frequency the signal is really on.  Or AROUND the 
multiple of the frequency the signal is really on, as can be seen from 
RBN spots.
CT1BOH has shown multi-multis who might find themselves behind DR1A in 
the next CQ WW the basis for making the same complaint.
I found it easier to see the spurious responses of the various SDR 
architectures from looking at RBN spots on weekdays, as the few 
DXpeditions or special event stations that might actually be on >1 band 
simultaneously are easy to find/exclude.
Figuring out which RBN spots or signals in a recording from a SDR are 
actually there as the station has >1 transmitter QRV or is really a 
fecal signal - or is just a spurious response of the SDR - should make 
for a good challenge.
73, ex-VR2BG/p.

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