[EIDXA] K3 Intermod

Thu Apr 19 11:38:27 EDT 2012

Thanks for your thoughtful and informative contribution, Rick. Yes, I had
the dreaded PWR ERR fault on my K3 toward the end of  HK0NA. It turned out
to be burned pins on the PA cable from too many RTTY calls on too many bands
; )

Nelson, KU0A

-----Original Message-----
From: reheinri at rockwellcollins.com [mailto:reheinri at rockwellcollins.com] 
Sent: Thursday, April 19, 2012 9:15 AM
To: Nelson Moyer
Cc: eidxa at qth.net; eidxa-bounces at mailman.qth.net
Subject: Re: [EIDXA] K3 Intermod

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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