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Re: New overview ARRL/QST Product Reviews

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  • PA1HR
    Hello Nico, I would be glad to change the figures when they have been published in ARRL/QST, because this is my source. What Jay sent me I immediately
    Message 1 of 66 , Sep 1, 2011
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      Hello Nico,

      I would be glad to change the figures when they have been published in ARRL/QST, because this is my source. What Jay sent me I immediately corrected in my overview.

      Otherwise Mr. Icom, Kenwood, TenTec, Yaesu, etc. will ask me to change their figures too...

      I follow discussions where Rob Sherwood is being involved with more than great interest, but only act according the publications in ARRL/QST.

      73! Hans PA1HR.




      --- In perseus_SDR@yahoogroups.com, "iv3nwv" <nicopal@...> wrote:
      >
      >
      >
      > --- In perseus_SDR@yahoogroups.com, "PA1HR" <hans@> wrote:
      >
      > > I corrected my overview and just published it.
      >
      > It's still inconsistent, Hans
      >
      > If you understand the figures you have published and if you agree that the sensitivity of a receiver has nothing to do with a two-tone test signal spacing you have the following options:
      >
      > 1) Correct the Perseus IP3@2kHz.
      > If the DR@2kHz is 3 dB less than that at 20 kHz spacing, the IP3 should be 4.5 dB lower than published, that's to say 30.5 dBm and not 35 dBm.
      >
      > 2) Correct the Perseus DR@2kHz.
      > If the IP3@2kHz does not differ from the 20 kHz value, the DR@2kHz should equal the value at 20 kHz spacing.
      >
      > I leave the choice up to you, but if you prefer the option #2, you should place the Perseus at rank 4 instead of rank 7.
      > Leaving the table as it is would be the worst option.
      >
      > You can also compare ARRL figures with those published by Rob Sherwood:
      > http://www.sherweng.com/table.html
      >
      > Rob did not measured any difference in the DR figure of Perseus when the spacing is changed. Which is what usually happens in a direct sampling receiver.
      >
      > 73s
      > Nico / IV3NWV
      >
    • df9ic
      Hi Leif, I agree that my two tone IMD2 example was wrong. As long as I test with nearly perfectly periodical signals (thus with a very small bandwidth) there
      Message 66 of 66 , Sep 18, 2011
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        Hi Leif,

        I agree that my two tone IMD2 example was wrong. As long as I test with nearly perfectly periodical signals (thus with a very small bandwidth) there is always enough oversampling for all spectrum components.

        > I do not understand the theory behind this statement,
        > (or I do not understand the statement.) More relevant
        > is that I find something else when actually doing the
        > measurement:-)

        I just wanted to express that NL reduction by dithering needs a high ratio of the dithering bandwidth (finally limited by the sample rate) to the signal bandwidth (RX bandwidth). While a linearization scheme working with postdistortion based on a physical model of the ADC can be inherently wideband.

        But I agree that this has no relevance for shortwave reception of narrowband signals.

        Henning
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