A Front-end with an IIP3 > +50dBm ?

[I7SWX]

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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[Geoffrey Mackenzie-Kennedy-2]

Thanks Gian. At this QTH, which is in the first hop zone of 40m BC signals
on their way to N.America, the receiver's IMD3DR needs to be > 110 db approx
at 2 kHz spacing if used for weak signal SSB DXing above 7130 kHz. Of course
the LO must be very quiet.  The big problem I have here is BC transmitter
phase noise and the enthusiastic levels of modulation some use especially
when broadcasting music.

The old mixers might be fighting back but I don't think that they will win
:-)

73,
Geoff
GM4ESD


Giancarlo Moda <[hidden email]> wrote:
To: <[hidden email]>

> 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.

<snip>


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