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2848Re: Image question

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  • applewiz2000
    Jun 23, 2013
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      Hi Tom,,

      I don't think 0.4dB will make any difference. The algorithm (not that I have detailed knowledge of it) should be able to cope with small amounts of imbalance as one of it's major "raisons de etre".

      It's a fair bet that the Flexradios do not always have <0.3dB amplitude match between I/Q channels across all HF bands.

      I have not used PSDR-IQ V1.12 for years. The V2.5.2 version gets >40dB most of the time. Only Christos can really answer how good relatively the 1.12 rejection algorithm is compared to V2.5.x.

      Excellent to see a product I designed in good use. Time will tell if the Mitsubishi RD16HHF FETs outlast the Heathkit SB220 !!

      73s, Rob.

      --- In powersdr-iq@yahoogroups.com, tom <loeblt@...> wrote:
      > Hi Rob,
      > Your amp is still humming away here and the 20 watts drives my SB220 to
      > about 300 watts out.
      > I saw some numbers on an old posting from Bob, g8voi, that stated that
      > even a .4 db difference in the channels can degrade the image rejection
      > to the low 30 db range, so I was a bit concerned. I am somewhere around
      > 25 db rejection at the moment.
      > I thought perhaps I could insert a small pad in one channel to equalize
      > the audio between the SR and the PC audio card rather than tearing into
      > the Softrock but that may wind up being the only option.
      > As Christos suggested, the PSDR V12.20 EIA button seems to work very
      > well for me at the moment.
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