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!
Direct HF sampling ADC RX like QS1R or Perseus with 16 bits has dynamic
range over 100 dB with a single, clean XO and no inherent images. This is
several orders of magnitude better then single bit QSD.
We are dealing with low error rates and further processing would reduce
insertion mistakes while increasing omissions. I like to catch erronious
ones - HI.
73 de Mario, S56A, N1YU
----- Original Message -----
From: "Brett Graham" <vr2bg@harts.org.hk>
To: <cq-contest@contesting.com>
Cc: <s56a@bit.si>; <ct1boh@gmail.com>
Sent: Sunday, July 21, 2013 3:19 AM
Subject: Re: [CQ-Contest] Understanding the dynamic error free RBN algorithm
S56A said:
One of my posts was censored so I repeat again - the main problem of RBN
are
cheap QSD 0IF RX with I/Q images due to sampling in the middle of CW
bands.
Just make QS1R requirement for RBN connection and live happily ever
since!
Not true - that the cause of wrong-frequency RBN spots can be attributed
to I/Q gain/phase unbalance of QSD SDRs.
There are a number of mechanisms involved, depending on the SDR used.
Parroting that it is all due to just one mechanism & only with one
particular receiver architecture will not change this.
QS1R is unique in that it is not QSD, yet it has the problem of spurious
responses that look like the one mechanism that keeps getting blamed - a
mechanism that shouldn't be seen with that particular receiver's
architecture.
And don't forget, we have already been told that wrong-freq RBN spots are
all due to fecal signals.
Everything is what you are told it is & what you are allowed to say
yourself is decided for you!
-ex-VR2BG/p.
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