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