Much different from the OMNI V?
----- Original Message -----
From: "Bill Tippett" <btippett@alum.mit.edu>
To: <tentec@contesting.com>
Sent: Wednesday, April 13, 2005 18:30
Subject: [TenTec] Orion Synthesizer Design
> W3ULS:
> >Can someone explain the seemingly large discrepancies between the 1993
> QST transmit composite noise and the 2003 Ten-Tec phase noise graphs for
> the OMNI VI?
>
> It could simply be poor resolution of the photo
> of the 1993 spectrum analyzer plot. Compare the following:
>
> January 1993 QST Review of Omni VI, photograph on page 5...
> http://www2.arrl.org/members-only/prodrev/pdf/pr9301.pdf
>
> ...to plot on p. 18 of the Omni VI+ Expanded Test Report from
> 1997. It looks much better even though I expect the synthesizer
> designs (VI versus VI+) are basically identical.
>
> http://www2.arrl.org/members-only/prodrev/pdf/lab/omni-6.pdf
>
> Orion's phase noise below 2 kHz is a major contribution.
> Assuming 130 dBc/Hz, and adjusting 27 dB for noise bandwidth,
> this means Orion's phase noise is -103 dB at 2 kHz using a 500
> Hz bandwidth filter. By comparison, both the Elecraft K2
> and Icom IC-7800 had IMD that was "phase noise limited" at
> 2 KHz spacings using 500 Hz bandwidths. Sherwood's IMD
> measurements of 80 dB at this spacing implies the phase noise
> of both rigs were about 23 dB worse than Orion at 2 kHz.
>
> http://www.sherweng.com/table.html (see footnote "f")
>
> This also indicates why adding narrow roofing filters
> alone (e.g. new Inrad for Omni VI or Yaesu MP) can only go
> so far without running into phase noise limits of the basic
> synthesizers. Even more amazing is that Orion holds <130
> dBc/Hz down to 200 Hz spacings! This means that a very
> narrow filter like the 600 Hz Inrad #762 can be used to
> full advantage at extremely narrow spacings without any
> degradation due to phase noise limiting.
>
> In looking at the article, I see it was written July 21,
> 2004. I wonder if Ten-Tec used the time before publicly
> releasing it to apply for patents? I sure hope so! This
> is a REAL contribution to the state-of-the-art, unlike the
> unabashed marketing HYPE coming from other manufacturers.
>
> 73, Bill W4ZV
>
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