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...-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