[hpsdr] Not HPSDR - G3SBI H-Mode Mixer as tested by PA3AKE

[Giancarlo Moda]

Hi All,

If you like to know more about D’MIXER that removed
the mixer from the most critical stages in a receiver
see what Martein Bakker, PA3AKE, has just published; a
magnificent document regarding his evaluation of Colin
Horrabin’s "H" mode mixer under various test
conditions and using many different transformers and
active devices. He spent thousands of Euros on proper
test equipment, and as many hours obtaining his
published    results. This is the real way we should
do measurement but certainly it requires a lot of
investment in $$$$ and working time and also
knowledge. Martein’s document has a lot of pages with
a lot of information and it is a good reading for
peoples that know what he is talking about and also
for people that want to learn. This is a sharing of
information and knowledge that sometimes is missing in
our amateur radio environment. As Harold Johnson,
W4ZCB, stated: I commend the read to your attention,
LOTS of meat in the   pages. You can get the document
at:
    
   
http://www.xs4all.nl/~martein/pa3ake/mixers-overview5.pdf
  
I am sure you will see that Harold is right, there is
a lot of meat to chew and digest too. The comparison
is not only associated to the FST3125 switches but
there is a very interesting comparison with modern
video switches.
  
A good friend of mine, Eraldo Sbarbati, I4SBX, has
done a similar work during 2005 winter. A lot of work.
He has made tests on commercial mixers and then on the
H-Mode with the 3 transformers  (G3SBI original
configuration, used in the CDG2000) and the 2
transformers (I7SWX simplified version, used in the
STAR) using various balun cores (size, material and
turns configurations) using homebrewed transformers. 
He has also checked where the mixers loose the 1:3
ratio. I4SBX has started the publication of these
reports in the Italian Ham Magazine RKE, Radio Kit
Elettronica, since this past summer. The final two
articles fully dedicated to the H-Mode Mixer, with
particular focus on the two transformers version, are
expected to be published in the March and April 2007. 
Eraldo’s tests include the divide by two (74AC74), and
fundamental squarers (using 74AC86 XOR and LVDS
receivers). The comparison is also referred to the
super CDG2000 RTX, front end and post-mixer roofing
filter.

 It will not be possible to make the translation from
Italian into English of all six issues due to
copyright and the work required. I will discuss with
I4SBX any possibility of publishing a digest of his
work, including his tables and graphics produced using
the N2PK VNA. You will be kept posted 
 if 

  
G3SBI H-Mode Mixer invention has still a lot to give
...  Thanks so much Colin!
  
  73 and enjoy PA3AKE’s document.
  
  Gian
 I7SWX
 



 
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