[hpsdr] Not Hpsdr - A Front-End with an IIP3 > +50dBm ?

[Giancarlo Moda]

Dear friends,

A Front-End with an IP3 over +50dBm? 

Some of you may think 
”it’s a joke ! Gian ‘s brain
got heated-up by the South Italian sunshine” 
.
Maybe
.

Our friend Martein, PA3AKE, as you know, has done
quite an important work on looking and measuring
performances associated to the H-Mode Mixer with
different kind of switches starting from the FST3125
and ending with the FSA3157, resulting with IP3 around
+50dBm. But what can we do with a mixer like that when
front-end Band pass filters may have problems to reach
an IP3 of +40dBm (see the CDG2000 input coils and
transformers IMD limitation) without talking about the
post mixer roofing filter that may not even reach an
IP3 of +30dBm.

Well Martein has been continuing his silent work on
input Band Pass Filters and roofing xtal filters. He
has just published his findings on the input BPF, at
the moment the one for 40 meters band, and more
important how to bring the roofing filters IP3 over
+50dBm !!!
YES
 maybe my brain has been heated up but Martein is
living in Holland and the sunshine heat is more
mitigated there 


He still has to do some more work, particularly on the
front-end BP filters, but he has certainly done a few
things very important:

1)	The result is an MDS of -133dBm in SSB bandwidth
and an IIP3 of +51,2dBm resulting in an IMD3DR of
122.8dB on 40M. !!!!

2)	He has put a lot of efforts to write the associated
documentation for the benefit of all of us. You will
be surprised when reading all his measurements and how
he solved problems.

3)	As Colin Horrabin, G3SBI , the inventor of the
H-Mode Mixer, said: Martein’s effort is the first he
knows to break the 120dB IMD3DR boundary!!! (real life
figures not simulation)

Martein has also rearranged and updated is web page,
enjoy the visit:

http://www.xs4all.nl/~martein/pa3ake/hmode/index.html

The old mixers are fighting back Hi!

73

Gian
I7SWX



       
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