[TenTec] Corsair II PTO Problems

[Kevin Purcell]

The Paragon (I and II) used a "normal" 4 octave PLL synthesized LO  
(with all the usual problems of increased phased noise) to get GC  
coverage.

The Omni V (and VI) on the other hand used a narrow range VHF VCO  
(198.2 to 221.2MHz with 400Hz steps divided by 40 to get 4.97 - 5.53  
MHz in 10Hz steps) PLL synthesized VFO (to reduce phase noise) that  
was then mixed with crystal generated to generate the LO. Rather like  
the PTO + XO LO generation in the earlier Omnis, Corsairs, Argosies,  
Deltas, etc. This reduced the phase noise in the LO.

Sherwood measured the phase noise of the Omni V as -134dBc at 10kHz  
from the carrier. The ARRL review the Omni V (composite) noise  
spectrum is very flat (and actually a bit higher than the Sherwood  
number if my eyeballing the SA display is right). The Paragon is much  
more sloped (though the ARRL review scan you can't see the SA  
fiducial marks).

There are other differences too (e.g. see this link)

<http://tentecwiki.org/doku.php?id=563>

> The phase noise performance of the Omni-VI vs. Paragon II is -20db  
> better as well.
>

I think this is at close separations around 2kHz.

On Nov 28, 2007, at 11:43 AM, Rick Denney wrote:

> The Paragon, which was Ten Tec's first general-coverage receiver. The
> Omni V appear a year or two later, with a ham-bands-only receiver.
> Both used digitally synthesized VFO's.

--
Kevin Purcell
kevinpurcell at pobox.com