[Elecraft] SSB IMD

[Jan Erik Holm]

Yes I´ve seen those figures, there are are lot of
data from component manufactures however by the
time we see the finished product data doesn´t
even come close.

I tried to look for the data on the FT-990 that
K6LL informed about but couldn´t find it. I was
thinking what reference level they used, I think
I remember ARRL changed their procedure, the -38
prity well could be -32 in real life.

However, something struck me, why is it we see
this big variation in data on the IMD3? We have
a spread between -38 to -24 dB. A number of
people has measured below -30 dB and as far as
I know "only" one around -38 dB. Who is right
and who is wrong?
Is there something critical in the radio that
gives this outcome? Critical adjustment perhaps?
Is it very sensitive what PS we use (ala W4ZV)?

As I said before, here I am first time on 20m
SSB and people report trash around my signal,
i e bad IMD. However at that time I had K3 at
120W, aftter I´ve made measurements and it
looks like something slowly starts to happen
at 80W.
Also I have myself heard K3´s on SSB with "trash"
around the signal "however" I have also heard
K3´s that did NOT have that.
So what´s going on here, I´m getting reel puzzled
and frankly quite tired of this.

I wish there would be a "service manual" available,
like there is for any Japanese rice box. I mean
a manual that contains all data for all adjustments.
Why not??

/ Jim SM2EKM
---------------------------
Joe Subich, W4TV wrote:
> 
>> Jan Erik Holm wrote:
>>> Bill and others, hold on and think about these
>>> figures. -35 to -38 dB IM3 !! We are dealing
>>> with 2SC2782 transistors operating at around
>>> 12V DC. I say no more, the knowledge and intelligent 
>>> individual will understand.
> 
> I would be careful here ... the Toshiba 2SC2879 data sheet 
> clearly does -38dB IMD at 60 watts with VCC=12.5V.  There
> are certainly devices capable of that level of performance  
> means that there are devices capable of that level just as 
> there are devices capable of similar levels of performance 
> at 120-140 watts per device with Vcc=28V. 
> 
> I would expect the 2SC2879 to also be capable of this level 
> of performance ... if not, I would have expected the design 
> of the KPA3 to have been based on another device. 
> 
> 73, 
> 
>    ... Joe, W4TV 
>