[CQ-Contest] Rig Comparisons for Transmitter Noise

David Siddall hhamwv at gmail.com
Wed Sep 10 09:51:55 EDT 2014


With regard to transmitted trash and technology, at the ARRL Centennial
convention this summer NR0V received the ARRL Technical Innovation Award
for developing his "Pure Signal" software.  It runs on digital rigs such as
the Anan and any other with open source software, and with last week's
announcements from FlexRadio providing an open path into their 6000 series,
undoubtedly some form of adaptive predistortion for those radios will be
available soon.  Others will follow.  One nice thing is that continual
improvements will be implementable rapidly as new amateur transmitters
increasingly enter the digital domain.

Maybe the larger issue is the disincentive to run clean signals.  It is a
typical "tragedy of the commons" situation.  Contesters running NR0V's Pure
Signal would enable OTHERS to hear the weak ones, but would be
disadvantaged by competitors running their older technology radios (such as
the FT1000MP Mark IV as you point out) by trashing the frequency used by
the operator with the "pure signal".  In this regard, the recent rules
change in the CQ contests requiring at least halfway decent transmit
signals is a small step, and more importantly a push in the right direction.

As an aside, in this year's ARRL phone DX contest I had to substitute out
my Flex 6500 at the beginning of the contest (due purely to operator error
I later found) and I only had an FT1000MP Mark IV available.  Fortunately
it was SSB, not CW, but even then I ran it in class A hoping it would be a
little cleaner.

73,  Dave K3ZJ

On Sun, Sep 7, 2014 at 5:28 PM, David Siddall <hhamwv at gmail.com> wrote:

> Jim,
> Good stuff, thanks!
> I also recommend K3NA's article on adjusting SSB audio chain.  While
> specific to Orion, the principles are adaptable any any rig.
> http://www.k3na.org/articles/Transmit%20audio%20adjustment.pdf
> 73, Dave K3ZJ
> On Sun, Sep 7, 2014 at 1:13 PM, Jim Brown <k9yc at audiosystemsgroup.com>
> wrote:
>> Over the last decade or so, Rob Sherwood's extensive work on receiver
>> performance has done much to improve the receivers in modern rigs, but
>> transmitters have been sadly neglected.
>> A month or so ago I began work on a project to compare ARRL test data for
>> selected rigs, focusing on the trash they generate. I shared an early
>> version of that work on the Elecraft reflector, and it seems to have found
>> it's way to Yaesu, who has just put new firmware on their website to
>> improve the CW waveform.
>> I've done a lot of work on the piece since then, and it's near its final
>> form. If you're thinking about buying a new rig, it should give lots of
>> food for thought.
>> http://k9yc.com/TXNoise.pdf
>> Also, if you haven't already done so, see the slides for K6XX's excellent
>> presentation on Signal Cleanliness, which, among other things, shows how we
>> can set up and operate our existing rigs to produce a cleaner signal.
>> k9yc.com/K6XXAmpTalk.pdf
>> 73, Jim K9YC
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