Slightly better performance than the NorCal 30..grin. 100 db image
rejection, wow! It must have one heck of a balanced mixer, I haven't been
paying attention to commercial gear at all, but nice to see a commercial
direct conversion receiver. I have been thinking for the last several month
about designing and building a direct conversion receivers with a Tayloe
mixer, followed by a DSP for audio filtering. Looks like they beat me to
it....
Cecil
KD5NWA
-----Original Message-----
From: tentec-admin@contesting.com [mailto:tentec-admin@contesting.com]On
Behalf Of Adam Farson
Sent: Wednesday, October 30, 2002 11:25 PM
To: Ten-Tec Contesting
Subject: RE: [TenTec] Re: TenTec digest, Vol 1 #729 - 11 msgs
<<...Tayloe quadrature mixer direct to the A/D and DSP...>>
The Rockwell-Collins 95S-1A receiver uses an image-reject I/Q mixer driving
the ADC at zero IF.
http://www.wa3key.com/95s1.html
Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/
Icom FAQ site:
http://www.qsl.net/icom/
-----Original Message-----
From: tentec-admin@contesting.com [mailto:tentec-admin@contesting.com]On
Behalf Of John Buck
Sent: Wednesday, October 30, 2002 19:44
To: tentec@contesting.com
Subject: [TenTec] Re: TenTec digest, Vol 1 #729 - 11 msgs
Jim,
OUCH! True but nasty. George will now have to try to recover. Watch out.
I think an interesting alternative approach is a Tayloe quadrature mixer
direct to the A/D and DSP. It seems to have excellent linearity and
dynamic range and even acts as a very narrow band front end filter. In
this case, the roofing filter can possibly be a digital brick wall low
pass operating at the high side of the received bandwidth. No other
stages are required except the 4X VFO and divider and some gain before
the A/D.
Aloha,
John KH7T
Jim, you wrote:
The argument that filters in the front end of a heterodyning
receiver are not needed if "everything" is absolutely linear
is just not so. The mixer is not linear, so an image reject
filter is NEEDED. And it might as well contribute to the
narrowing of the spectrum of energy to be handled by
the entire following system as well as doing the job of image
and spurious signal product rejection. To imply that the use
of narrow, muti-pole crystal lattice filters following the first
mixer is a "cover up" for poor linear design characteristics
of the front end or following stages, is just not being technically
honest.
Lots of words, hope this is understandable.
73, Jim KH7M
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