K3 SSB transmit spectral purity?

[Bill VanAlstyne W5WVO]

An interesting post just appeared on the Omni-7 board from Aussie Craig Dickson, VK3HE. He writes, in part:

"...[T]he second issue is SSB Transmitter spectral purity. [To me] it is still unacceptable to have SSB transmitters with 2-Tone IMD figures of -20 to -26 db below pep 3rd order... In my mind its a pity that the designers of the Omni 7 did not see it as a high design priority to make sure [it] had [a] transmitter that matched its excellent receiver performance. To me its of equal amazement that the designers of the K3 also chose to ignore this issue. If either the K3 or Omni 7 met commercial or NTIA standards for SSB signal purity it would have opened new markets and increased sales for both Elecraft and Ten Tec."

( Actually, a pretty audacious post for a guy whose QRZ page says "Inactive. I don't QSL." <LOL> )

In any case, all judgment aside -- We've seen very little discussion of the K3's transmitter design, and that's understandable in light of the tremendous breakthrough the guys have made in receiver performance versus price point. And I have no idea if Craig's statements in regard to the K3 have any merit at all. But I'm curious as to how Wayne and Eric would respond to Craig's implication that the K3's transmit purity leaves something to be desired. Guys, do you think Craig makes a valid point, or not? And if he does make a valid point, is this just a matter of marketability -- of the customer being unwilling to pay extra for technological refinements that, at the end of the day, don't directly affect his performance experience on the air? Or to put it another way: >From the market standpoint, the receiver has to be great, but the transmitter only has to be good enough? If everyone used SSB transmitters that met commercial standards, would the ham bands have less QRM overall?

Bill / W5WVO
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[Craig-89]

My  comments on the K3 have no merit since we don't
any  data on the K3's  IMD performance. However if its
  close to my K2's performance its nothing to brag
about. However how much can you expect from pair of
2SC2879's?

I wonder whats the point of pursuing goals for
receiver design that hits the limit of technology
when  all  this performance can be rendered useless by
 operators who are using transmitters that have  very
poor SSB transmitter IMD performance. There is also
the question of   design compromises   between the
needs of battery powered portable operation and fixed
station use. Clearly you don't need spectacular IMD
performance if you running a wire in a tree with 10
watts.

While their has been a relentless pursuit  towards
eliminating  keyclicks, one  has to wonder why the
same  objective has not been so hotly pursued for SSB
transmitters. There  is a good database of SSB
transceiver performance measurements  on SM5BSZ's
webpage.

http://www.sm5bsz.com/dynrange/rig_compare.htm

If you dig through the data you will find old data
there for the K2, and recently  some SSB IMD data for
the new Orion 2. Theres also some data there for the
IC7000, and as you will note the IC7000 has better
close in IMD performance than the Orion 2. While its
great hearing that an Orion user cannot hear SSB
stations close to their operating frequency because of
the excellent receiver, however  you may not always be
sure that your SSB transmitter may not be  causing
unnecessary interference to a nearby station that may
not be receiver performance  related.  This issue is
no different to the keyclick debate. However  you will
 notice in the Authors comment that he clearly states
that the Orion does not have the flawed ALC induced
splatter problems that  probably most Japanese radios
have. Even the IC7800 has this  problem.

So in the context that my post was made comparing any
of the new radios, the K2, K3 and almost any  of the
current top of the line radios they are all probably
similar in performance with no particular one standing
out. The Hilberling has a claimed IMD performance of
-36 below pep according to  the new brochure in QST.
This is for a radio operating operating on 13.8 volts.
-36 db below pep is a very good number for a 12 volt
radio. Again we  have no data and this could just be
commercial hype.

I have asked these questions in email about the K3's
final amplifier design and performance i have not
received  any further information. I guess we will
just have to wait for the ARRL's review.

Well insofar as my operational status is concerned i
am largely inactive  because of work reasons. However
i do operate now and then with my K2, so whats funny
about that? As for the QSL'ing i am  just honest
enough to state that i am not interested  in
collecting QSL's saving whoever sending money down a
black hole. I think thats considered good operating
practice  or manners.

Craig
VK3HE



--- Bill W5WVO <[hidden email]> wrote:

> An interesting post just appeared on the Omni-7
> board from Aussie Craig Dickson, VK3HE. He writes,
> in part:
>
> "...[T]he second issue is SSB Transmitter spectral
> purity. [To me] it is still unacceptable to have SSB
> transmitters with 2-Tone IMD figures of -20 to -26
> db below pep 3rd order... In my mind its a pity that
> the designers of the Omni 7 did not see it as a high
> design priority to make sure [it] had [a]
> transmitter that matched its excellent receiver
> performance. To me its of equal amazement that the
> designers of the K3 also chose to ignore this issue.
> If either the K3 or Omni 7 met commercial or NTIA
> standards for SSB signal purity it would have opened
> new markets and increased sales for both Elecraft
> and Ten Tec."
>
> ( Actually, a pretty audacious post for a guy whose
> QRZ page says "Inactive. I don't QSL." <LOL> )
>
> In any case, all judgment aside -- We've seen very
> little discussion of the K3's transmitter design,
> and that's understandable in light of the tremendous
> breakthrough the guys have made in receiver
> performance versus price point. And I have no idea
> if Craig's statements in regard to the K3 have any
> merit at all. But I'm curious as to how Wayne and
> Eric would respond to Craig's implication that the
> K3's transmit purity leaves something to be desired.
> Guys, do you think Craig makes a valid point, or
> not? And if he does make a valid point, is this just
> a matter of marketability -- of the customer being
> unwilling to pay extra for technological refinements
> that, at the end of the day, don't directly affect
> his performance experience on the air? Or to put it
> another way: >From the market standpoint, the
> receiver has to be great, but the transmitter only
> has to be good enough? If everyone used SSB
> transmitters that met commercial standards, would
> the ham bands have less QRM overall?
>
> Bill / W5WVO
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>

 
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