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
