[EIDXA] K3 Intermod

Thu Apr 19 10:15:05 EDT 2012

Nelson,

I hesitate to enter this discussion/debate for many different reasons, 
but...

I have some experience with mixing K3s and other radios at PJ2T.  So what 
I am about to offer is direct experience/observations from someone who has 
worked to put together a station infrastructure for Multi/Multi 
competition.

1)  The K3 has a very capable receiver.  It is quiet and for that reason 
is regarded as one of the most "fatigue free" radios.  The fact that it 
has a second receiver with the same design for split, diversity, etc. 
makes it unique and contributes to its status as highly capable.

2)  The K3 has an outstanding synthesizer with very low phase noise.  This 
helps with a variety of mixing products that make multi-transceiver 
operation possible.

3)  For normal, typical ham station installations it is likely one of the 
best, most cost effective solutions.  It has high praise by many for its 
overall performance.

Now having said that, I will offer its challenges.  It seems to have spurs 
and unusual antenna "re-radiation" characteristics that are dependent on 
how it is assembled.  I have had the opportunity to sit three different 
K3s side by side, different releases of software and hardware variants, 
and assembled by different people.  Each had different spurs and birdies 
and showed up in other receivers on other bands.  Now at PJ2T we go 
through an extensive planning and pre-operational exercise to select 
specific frequencies for each band to minimize interference.  We have stub 
decoupling/filters.  We have cascaded bandpass filters, and as you note we 
have an extensive copper strap interface that is common for the four main 
operating positions.  We have to jump through pretty difficult hoops when 
we add a 5th station for a specific contest.  But the key is that we pick 
our frequency of operation based on extensive pre-contest testing.  We 
listen for not only harmonic relationships but also specific radio induced 
noise and strange signals that appear to be radio dependent.

We can mix FT-1000MPs, FT-1000 MkVs, FT-2000s, Omni-V, TS-930s, and 
IC-765s and each of these radios have different noise/emission 
"signatures" and we adjust accordingly.  The same thing happens when we 
bring the K3 on line.  The only difference is that once we characterize an 
FT-1000MP we can substitute another FT-1000MP and get the same signature. 
The same goes for most of the other compliment of radios.  but the K3 is a 
bit of an enigma in that there is no consistent noise/emission 
"signature".

I would bet that unless you stress an installation like a DX-pedition in a 
hostile environment, you would never know about these issues.  Now take 
the hostile Malpelo Island environment and it becomes very challenging. 
Poor/impossible common grounding between the A and B stations, heat, 
humidity, etc. - most transceivers would not do well.  Look at TS-930S 
which was a good radio during their heyday.  Great when operated on stable 
60Hz.  Take one to field day on a generator where the line frequency 
varied between 50-60Hz and the radio heated to the point where you could 
cook on it until the power dropped back.  Some of the Ten Tec radios would 
shut down in high humidity conditions.

So let's make this more personal on my part.  I struggle with the decision 
to move to a K3 for a few well documented reasons.  First I am a contester 
and that has its own challenges.  I love the receiver in the K3.  I love 
the completely separate second receiver - it has more versatility for 
split receive including diversity reception.  But I think what challenges 
me more than anything is that I have seen the hood up on more than one K3 
during a contest.  That is one thing if you have a backup, but if you 
don't then you lose while you make on line repairs or you throw in the 
towel.  The event that has me more challenged than anything with the K3 is 
the connector robustness.  We have had two power amplifier DC power 
connections fail during the high humidity operation at PJ2T - and I 
believe you have experienced a similar challenge.  I can better deal with 
a component failure than I can connectors.  I know broken is broken, but 
having built radios for my livelihood, I know connector choice is one of 
the critical design issues.  And I am challenged by tin plated connectors. 
 They fail.  So that is what is causing me the most consternation.

The fact that the radios did not fail on Malpelo speaks volumes for me and 
my decision.  I have used the new ICOMs like the IC7700 and personally I 
do not like them.  I have used the FT-2000 and believe there are better 
receivers out there.  But the bottom line is that everyone has their 
favorite for whatever reason.  You pay your money and you make your choice

So for Glenn and the Malpelo Team, they have their experience that will 
guide their decision making in the future.  For them and their style of 
operation the K3 may not fit their need.  For others it might.  You made 
your decision based on your research and preferences.  I will make my 
choice based on my criteria.  We may wind up with the same radio or not.

Rick

"Nelson Moyer" <ku0a at mchsi.com> 
Sent by: eidxa-bounces at mailman.qth.net
04/19/2012 08:04 AM

To
<eidxa at qth.net>
cc

Subject
[EIDXA] K3 Intermod

Glenn's indictment of the K3 receiver got me thinking about why HK0NA
experienced intermod and other K3 DX'peditions haven't reported that
problem. Could it be that that inadequate station grounding on the rock
could have been the culprit? I'm sure that the seawater ground at Ducie 
was
much more effective than anything they could have achieved at Malpelo,
considering that its solid rock. The only conductive material would have
been the guano and algae on the surface.

I know we all have our favorite radios, and I think Glenn likes ICOM, but 
to
issue a very public blanket indictment of the K3 based upon HK0NA 
experience
only seems a bit harsh to me. If ground issues were the problem, perhaps a
qualifier is in order before Glenn gives his talk at Dayton or wherever.

Nelson, KU0A

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