You've got THAT right, Phil !! But the closer you are to 90
degrees in the first place the less "learning" time. Fun stuff, this SDR.
The problem to solved is a sharp, fast tuning, BPF....not as sharp as
would be required for transmitting and FCC Tx specs, but not 5Mhz wide either,
and not requiring plugging, preferably automatic.
73 Kees K5BCQ
----- Forwarded Message -----
Date: Sat, 21 Jan 2006 09:30:00 +0800
Subject: Re: [softrock40] frequency sensitivity?
Yes and no! The phase does vary as you move away from
the frequency at
which the phase is exactly 90 degrees. With a
conversion receiver this would seriously degrade
your image rejection - as
an example an error of 0.1dB in
amplitude and 1 degree in phase will result
in a maximum image rejection of
However, with the software that is used with the SoftRock (Rocky,
etc) errors in I/Q phase and amplitude are automatically corrected by
software continuously 'learning' what the optimum settings are for ~80dB
image rejection. This is an incredible breakthrough and will
SDR's - I call it "the four lines of code that changed the
----- Original Message
From: "Marvin Moss" <mmoss@...>
Sent: Saturday, January 21, 2006 1:34
Subject: [softrock40] frequency sensitivity?
> Perhaps this
has already been covered, but since the 90 degree phase shift
> of the RC
combo is true only at one frequency, what effect does the phase
have as it increases or decreases as you get of the 90 degree
>from the softrock in
> That is, do you get increasingly poorer performance
> terms of images, rejection, sensitivity,
demodulation performance, etc. as
> you get farther away from the one
frequency where it is exactly 90
> No virus found in this incoming message.Edition.
> Checked by AVG Free
> Version: 7.1.375 / Virus Database: 267.14.21/235 - Release
No virus found
in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.375 /
Virus Database: 267.14.21/235 - Release Date: 19/01/2006