EMRFD Message Archive 968
Message Date From Subject 968 2007-08-23 07:41:11 Giancarlo A FRONT-END WITH AN IIP3 > +50dBm ? 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:
The old mixers are fighting back Hi!
973 2007-08-24 09:09:10 Ed Almos Re: A FRONT-END WITH AN IIP3 > +50dBm ? The approaches taken by this research in using large toroid cores to
increase IP3 are interesting and other people are using this
technique. If you examine the preselector PCB on the new Hilberling
transceiver you will see a very large toroid which has been fitted for
this very reason.
Some very good pictures are available at http://www.hilberling.de/
995 2007-08-30 08:38:53 jr_dakota Re: A FRONT-END WITH AN IIP3 > +50dBm ? WOW, good stuff ... Thanks for the link, I probably never would have
stumbled across this on my own
It even answers the questi