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Re: [linrad] Low phase noise LO

Dear Edson,

   I have built an I/Q system with two diode ring mixers, two very
low-noise op-amps for 14mhz.

   Local Oscillator is LC, stabilized with a PIC microcomputer.

   Quite cheap and a VERY good performer. Works very nicely with ISA audio

   My biggest problems are that many/most newer PCI sound cards are very
lacking and.

   Also, some versions of linrad crash?? Still haven't figured out
exactly what is going on. i.e.- lir00-48 works fine, lir00-50 just stops
when I turn on fft3 (I am not using fft2).

   just my 2 cents.

   It might be useful to start a thread on how to simply measure
performance of linrad type systems.

   warm regards,
   john, ni1b

On Mon, 3 Feb 2003, Edson Pereira wrote:

> Greetings!
> I am thinking about building a simple direct coversion IQ receiver and am
> pondering what would be a good local oscilator to use. I will either use a
> diode ring mixer or a Tayloe-like mixer. In both cases, from what I have
> read,the local oscilator should have low phase noise. A DDS would be
> convenient, but it seems that the phase noise is poor. Does any one have
> any suggestions? Would an AD9852 or AD9854 DDS be satizfactory? I don't
> what to make the circuit too complex.
> 73,
> -- Edson, 7n4ncl