FTDX5000 Design Flaw

[P.B. Christensen]

I just spent some time reviewing phase noise data for competing
transceivers.  The P/N plot at 1 kHz(Fc) and beyond of the FTdx5000 as show
in the December, QST product review looks no worse than the IC-7700,
IC-7600, Flex 5000A, Orion II, and Yaesu FTdx9000 series.  So, any design
limitation evident in the Yaesu FTdx5000 is something that needs to be
addressed by most manufacturers.  Arguably, the mediocre P/N result is
really a design limitation, rather than a design flaw.  I would think that
if the problem was pervasive, it would show at contest stations like K3LR,
where IC-7700/7800 transceivers are used.

But to your point, the K3 does excel in this metric and the competition
should do a better job with its future designs as well as placing more
importance on Tx IMD optimization.  Yaesu's success in their implementation
of Class A amp design is clearly evident -- but it's an inefficient way to
get to those Tx IMD numbers.

Paul, W9AC














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[Julian, G4ILO]

P.B. Christensen wrote

Yaesu's success in their implementation
of Class A amp design is clearly evident -- but it's an inefficient way to
get to those Tx IMD numbers.

Yes it would be nice to see more transceivers that are DSP based employ adaptive predistortion like expensive and feature-lacking but interesting ADAT ADT-200A. Could the K3 do that?

[Guy, K2AV]

In my K3, the two tone IM products are better at the output of the
100w stage than they are at the 10W point. There IS some serendipitous
cancellation going on.  But our excellent experience of side-by-side
K3's at IOTA on Core Banks, and the Field Day same band 40 m CW and
SSB stations separated by 300 feet, could not have happened in either
venue without the K3 TX already being very clean.

The adaptive predistortion would work for IM, but could not help out
with phase noise.  Personally, I'd put the priority on APD fairly down
until we start having common situations where the very low IM from the
K3 is troublesome.

73, Guy.

On Sun, Nov 21, 2010 at 1:02 PM, Julian, G4ILO <[hidden email]> wrote:

>
>
> P.B. Christensen wrote:
>>
>> Yaesu's success in their implementation
>> of Class A amp design is clearly evident -- but it's an inefficient way to
>> get to those Tx IMD numbers.
>>
>>
>
> Yes it would be nice to see more transceivers that are DSP based employ
> adaptive predistortion like expensive and feature-lacking but interesting
> ADAT ADT-200A. Could the K3 do that?
>
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> * G4ILO's Shack - http://www.g4ilo.com
> * KComm - http://www.g4ilo.com/kcomm.html
> * KTune - http://www.g4ilo.com/ktune.html
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/FTDX5000-Design-Flaw-tp5760598p5760648.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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[Joe Subich, W4TV-4]

>> Personally, I'd put the priority on APD fairly down until we start
>> having common situations where the very low IM from the K3 is
>> troublesome.

Transmit IMD can be improved significantly by operating the current
100 W amplifier at reduced power output and by updating the design
with a 48V supply/50V transistors for use with a real "fixed station"
supply.

Even using 24V transistors at 150W output with an 18V supply and 75W
output with a 12.0 V supply would go a long way to reducing transmit
IMD without all of the added complexity of APD.

73,

    ... Joe, W4TV


On 11/21/2010 2:54 PM, Guy Olinger K2AV wrote:

> In my K3, the two tone IM products are better at the output of the
> 100w stage than they are at the 10W point. There IS some serendipitous
> cancellation going on.  But our excellent experience of side-by-side
> K3's at IOTA on Core Banks, and the Field Day same band 40 m CW and
> SSB stations separated by 300 feet, could not have happened in either
> venue without the K3 TX already being very clean.
>
> The adaptive predistortion would work for IM, but could not help out
> with phase noise.  Personally, I'd put the priority on APD fairly down
> until we start having common situations where the very low IM from the
> K3 is troublesome.
>
> 73, Guy.
>
> On Sun, Nov 21, 2010 at 1:02 PM, Julian, G4ILO<[hidden email]>  wrote:
>>
>>
>> P.B. Christensen wrote:
>>>
>>> Yaesu's success in their implementation
>>> of Class A amp design is clearly evident -- but it's an inefficient way to
>>> get to those Tx IMD numbers.
>>>
>>>
>>
>> Yes it would be nice to see more transceivers that are DSP based employ
>> adaptive predistortion like expensive and feature-lacking but interesting
>> ADAT ADT-200A. Could the K3 do that?
>>
>> -----
>> Julian, G4ILO. K2 #392  K3 #222.
>> * G4ILO's Shack - http://www.g4ilo.com
>> * KComm - http://www.g4ilo.com/kcomm.html
>> * KTune - http://www.g4ilo.com/ktune.html
>>

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