[Elecraft] FTDX5000 Design Flaw

[Eugene Balinski]

The phase noise on the original Icom IC-751 (not the "A"
versions) was so bad that it was banned from our
multi-transmitter field day site.  Seems it took out a
number of bands when transmitting-.

Gene K1NR

On Sat, 20 Nov 2010 12:48:53 -0800
 "John, KI6WX" <ki6wx at pacbell.net> wrote:
> The ARRL is aware of this issue.  This problem was
> discussed in my 1988
> articles on phase noise in QST (March & April issues).
>  The article notes
> that a high phase noise transmitter degrades the
> performance of a low phase
> noise receiver to that of the transmitter.  This article
> started the ARRL
> making composite transmit noise measurements.
> 
> A strong signal (>S9+50dB) from a transmitter with
> broadband -130 dBc
> composite noise in a 500 Hz bandwidth reduces the
> receiver's blocking
> dynamic range to 103 dB.  Most top notch receivers show a
> blocking dynamic
> range of around 140 dB.  In this case, the dynamic range
> is reduced because
> the noise floor is increased.
> 
> I don't think most hams are aware of the problem.  If you
> have a nearby ham
> running high power and your receiver doesn't work well
> when they are
> transmitting, you just assume that the signal is too
> strong for your
> receiver.
> 
> This problem is like splatter or key clicks.  It doesn't
> impact the owner of
> the transmitter, but instead degrades the receiving
> environment of those who
> live near them.  There is little incentive for the owner
> of the high
> composite noise transmitter to improve their equipment.
> 
> -John
>  KI6WX
> 
> > 
> > The FTDX500 wouldn't be the only one, if a -130 dBc
> composite noise
> > number defines failure. If you have access to QST
> reviews, compare:
> > 
> > Flex 5000
> > FT-2000
> > Orion II
> > IC-7700
> > K3
> > 
> > all of which plot tx composite noise at 100 or 200 W
> out to 1 Mhz. You
> > can draw your own conclusions, but the FTDX5000
> apparently isn't
> > exceptional in that regard.  The Flex is no better than
> -120 dBc out
> > to 1 MHz, the FT-2000 is slightly worse than the
> FTDX-5000, and the
> > Orion II is no better than -130 dBc out to 100 kHz. The
> Icom rigs seem
> > to do a little better. The K3 performance indeed far
> surpasses the
> > others. I could find no comment on these numbers in the
> reviews.
> > 
> > Bob NW8L
> > 
> > > Why is this not sent to the Editor and Technical
> Editor or QST as
> > > well as the lead test engineer at the ARRL lab?  What
> was their
> > > response?
> > >
> > > If the radio's transmitted phase noise is that bad,
> Yaesu should be
> > > forced to recall all units currently in the field.
> > >
> > >
> > > 73,
> > >
> > >    ... Joe, W4TV
> > >
> 
>
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