Bill Dumke wrote:
> Art,
>
> Sounds like we might be comparing apples and oranges here.
>
> The SDR-1000 is traditional Tayloe. The SoftRock versions, so far, are
> not
>
The SDR-1000 is a not a PRIOR-ART detector. It is a version of the Van
Gras detector which D.H. van Gras published in QEX in 1990 on page 7-10
in the September issue NINE YEARS before the Prior-Art detector was
published (1999). The prior-art detector is old old old. It has been
published so many times it is not funny. We really do need to REFUSE to
call this what it is not. Motorola holds the INCORRECTLY granted patent
on this mixer. It is yet another living testimonial to what has gone
wrong with the patent office. They did NO investigation whatsoever on
the patentable claims with anyone who can have done a modicum of search
for prior art.
As to the apples and oranges, Art and I have been discussing this off
line and I agree that we are comparing the SDR-1000 to his simulations
of the softrock versions of the mixer. Functionally they nearly
equivalent with one really important difference, inherently balanced
versus inherently unbalanced.
Here are the basic differences and how they arise. In the Van Gras
derived QSD, each of 4 phases has a cap hooked to the load and
integrates and then holds this for 3/4 cycle at the LO. The
differencing is done in the OpAmp or instrumentation amplifier which
follows on the 0,180 capacitors and the 90, 270 capacitors to produce
I/Q respectively. In the softrock detector, the capacitor itself does
the summing and integrating as follows: A transformer is in front of
the two capacitors. It has a center tapped secondary and the center
tap is grounded. Each of the capacitors has one leg grounded. At 0
degrees the I cap is connected to the "top" of the transformer secondary
for a quarter cycle and at 180 the I cap is hooked the "bottom" of the
secondary for a quarter cycle. Similarly, the "Q" cap is connected to
the top and bottom of the secondary of the transformer at 90 and 270
respectively.
The QSD, with its four caps and use of differencing in an op amp/ ina,
produces an inherently balanced output. The Prior-art detector and the
Softrock produce inherently UNbalanced output. In my estimation,
Gerald made a mistake in not allowing for balanced audio output and
hooked the balanced output up to the tip,ring,ground for I,Q on a
standard sound card cable. I understand why, but I have always wished
it were not hard wired this way.
I love the softrock. It is just the greatest thing and Tony is one of
the all time super nice guys. I do not want anything I say to be viewed
as detracting from his work. I think he is doing amateur radio and swl,
etc. the greatest service by giving us this inexpensive yet good
performance receiver to show how well we can do with well constructed
software and inexpensive front ends. It really does make it hard to
justify $13000 for a radio as anything other than as a status symbol.
We have seen a very nice collection of offerings form Alex (Rocky),
KGK, SDRadio, Flex and I am sure others.
GO TONY.
Bob
> What does your simulation show with a traditional Tayloe design?
>
> Bill WB5TCO
>
> Robert McGwier wrote:
>
>
>> Art:
>>
>> Let me reiterate what it is we OBSERVE and can measure with the QSD in
>> the SDR-1000.
>>
>> We do /***NOT***/ see conversion loss increase as the frequency gets
>> higher. We see a nearly flat 1 dB insertion loss (to withing reason but
>> so close, just fogettaboutit).
>>
>> What we do see is a steady rise it the noise floor. If you put in a -70
>> dBm signal at 14 MHz, you got approximately the same converted voltage
>> as you do at 54 MHz with -70 dBm signal. The MDS gets worse, the
>> loss does NOT.
>>
>> Bob
>> N4HY
>>
>>
>>
--
AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,
NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman
Laziness is the number one inspiration for ingenuity. Guilty as charged!
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/soft_radio/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
