[Elecraft] FTDX5000 Design Flaw

Sat Nov 20 19:09:55 EST 2010

Hi Joe

A recall for Yaesu is the new FT6000! Yaesu's  past  history with the keyclick debacle makes me believe that a recall of any Yaesu product is very unlikely.

The FT5000 with its tuning birdies, image rejection and now wideband phase 
noise problems is fast becoming an expensive lemon. 

It is unlikely that the FT5000 will be used in any multi multi station with these phase noise problems. It will also make the FT5000 unusable for VHF contesting with transverters in Europe.  Wideband phase noise problems can cause huge problems for line of site VHF contesting. There are VHF radios that are worst than the FT5000, the Icom IC910H is one of them.

73
John

--- On Sat, 11/20/10, Joe Subich, W4TV <lists at subich.com> wrote:

> From: Joe Subich, W4TV <lists at subich.com>
> Subject: Re: [Elecraft] FTDX5000 Design Flaw
> To: elecraft at mailman.qth.net
> Date: Saturday, November 20, 2010, 8:10 AM
> 
> >> This transmitter when combined with a full power
> amp could wipe
> >> weak signals in an entire amateur band for anyone
> living within a
> >> few miles of the transmitter (see the math
> calculation below).
> >> While a number of other transceivers have this
> problem, I wouldn't
> >> expect a top of the line $6K radio to have such
> lousy composite
> >> transmit noise.
> 
> 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
> 
> 
> On 11/20/2010 12:08 AM, John, KI6WX wrote:
> > There have been a lot of comments on the reflector
> about the QST review of
> > the FTDX5000.  However, no one has noted a
> significant design flaw in the
> > transmitter that shows up in the review.  Refer
> to Figure 3 that shows the
> > composite transmitter noise.  It shows a noise
> level of -130 dBc/Hz from 10
> > kHz to 1 MHz (and probably beyond).
> >
> >
> >
> > This transmitter when combined with a full power amp
> could wipe weak signals
> > in an entire amateur band for anyone living within a
> few miles of the
> > transmitter (see the math calculation below). 
> While a number of other
> > transceivers have this problem, I wouldn't expect a
> top of the line $6K
> > radio to have such lousy composite transmit noise.
> >
> >
> >
> > This problem is created either in the radio's
> synthesizer or its transmit
> > amplification chain.  The K3 was specifically
> designed to minimize composite
> > transmit noise.  The K3 QST review showed a
> transmit noise level of -155
> > dBc/Hz at a 100 kHz offset.  This is 4 S-units
> less noise than the FTDX5000
> > at the same offset.
> >
> >
> >
> > This is not a theoretical calculation.  I know of
> one case of composite
> > transmit noise where an amateur transmitter wiped out
> weak signal reception
> > across an entire ham band in a receiver located
> several miles away.
> >
> >
> >
> > -John
> >
> >   KI6WX
> >
> >
> >
> >
> >
> > CALCULATIONS
> >
> >
> >
> > Assume that we have a FTDX5000 transmitting CW on 20
> meters followed by a
> > 1.5 kW amp.  The transmit power is +62 dBm. 
> At a 100 kHz offset, the
> > transmit noise is -68 dBm/Hz.
> >
> >
> >
> > Assume that the FTDX5000 transmit output is fed to an
> isotropic radiator (0
> > dB gain) on top of a hill and we have a receiver also
> with an isotropic
> > antenna in a valley with line of sight to the
> hill.  For directional
> > antennas, the sum of the antenna gains depends on
> where they are aimed and
> > could be greater or less than the 0 dB in this
> example.  For the moment,
> > we'll place the receiver 1 mile from the transmit
> antenna.
> >
> >
> >
> > The path loss between the transmit and receive
> antennas is 60 dB, which
> > implies the receive power of the transmit noise will
> be -128 dBm/Hz.  The
> > normal atmospheric noise on 20 meters is about -144
> dBm/Hz, which means that
> > the transmit noise will be 16 dB greater than the
> normal background noise.
> > This noise will be spread across the entire band
> whenever the FTDX5000 is
> > transmitting.  If it is transmitting CW, the
> receiver will hear noise
> > modulated in Morse code.  If it is transmitting
> SSB, the noise will vary
> > with the voice modulation peaks.  The receiver
> would have to be more than 6
> > miles away for the noise to drop to background
> levels.
> >
> >
> >
> > Another way to look at this problem is how many
> S-units would the show up in
> > a 500 Hz receive bandwidth.  The total power in
> the noise is -101 dBm in the
> > 500 Hz bandwidth.  S4 is -103 dBm, so the noise
> would be about a S4 signal
> > level.  Each time you halve the distance to the
> transmitter, the noise will
> > increase by 1 S-unit.  If you live 1000' from a
> FTDX5000, you could see a
> > noise level of S7.  You can reduce the noise by
> using a narrower filter, but
> > you would have to drop down to a 100 Hz filter to
> reduce it by 1 S-unit.
> >
> >
> >
> > This calculation was done with the transmit antenna on
> top of a hill so we
> > could use free space radiation to calculate the path
> loss.  If both antennas
> > are on a flat surface of earth, the path loss will be
> somewhat greater, but
> > the exact magnitude requires using antenna radiation
> software such as NEC-4.
> >
> >
> >
> >
> >
> >
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