On Sat,10/18/2014 6:06 PM, Randy Thompson K5ZD wrote:
It is true that some rigs (depending on how they are operated) can produce
signals that appear wider than normal. Can you think of a way to express
this in technical terms rather than using a K3 as a reference. Contesting
needs to have a dialog around what is the accepted standard for signal width
or "cleanliness".
What test equipment would some use to evaluate their own signal in the
shack?
What would be a good test standard for someone listening to capture the
essence of the signal quality?
Randy, K5ZD
-----Original Message-----
From: CQ-Contest [mailto:cq-contest-bounces@contesting.com] On Behalf Of
Jim Brown
Sent: Sunday, October 12, 2014 4:57 PM
To: cq-contest@contesting.com
Subject: [CQ-Contest] Handicap For Dirty Rigs
In my study of the TX Noise produced by current transceivers, I noted the
significant advantage enjoyed by users of dirty rigs by pushing other
stations away from their TX frequency, and making it difficult (or
impossible) for stations to S&P near them. Consider the lineup of
hundreds of NA stations in the 15 kHz 160M JA window, and comparable
conditions from east coast to EU. One FTDX5000D burns five K3 channels;
one ICOM 7800,7700, 7600, burns three. I run a K3 and a Ten Tec Titan,
which is quite clean. I've established a run frequency for JA only to run
off by a guy with a dirty power amp 700 Hz away.
Competitors using these dirty rigs should pay the price competitively. I
propose a scoring penalty of 15% to the users of FTDX5000 and other Yaesu
rigs in that family (study ARRL data to understand why that's valid), and
10% to users of IC7800, 7700, 7600. KE1B, who uses a 7600 to drive a
solid state amp, wipes out 10 kHz of whatever band he is on for me on CW,
more on SSB. I'm not a WRTC competitor, but K6XX is, and his dirty TX
hurts Bob worse than me. By contrast, Bob and I, with K3s and tube amps,
can work 500 Hz apart and barely know the other is there. And Bob is
three miles closer than KE1B.
Is this fair? I contend that with the right to run high power comes the
responsibility to produce the CLEANEST signal consistent with the state
of the art. K3 has established the state of the art, and preliminary data
from the mfr suggest that Flex 6000-series may be as good. Kenwood
TS590S is 10 dB worse, at a very modest price. I contend THAT is state of
the art, and that ICOM and Yaesu fail to meet it.
Yes, I'm saying that users of these dirty rigs need to replace them with
cleaner ones. In 2008, I sold a pair of loaded FT1000MPs at significant
loss to be replaced by K3s. I did this because I could see from specs
that I needed to do that to coexist with my neighbors. Before that, I
owned a pair of TS850s and K2s. All sold.
And remember -- this is ARRL's data, not mine. :)
From my days in the civil rights movement of the '60s and '70s -- "if
you're not part of the solution, you're part of the problem!" I've dumped
my dirty rigs -- how about YOU?
73, Jim K9YC
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Hi Randy,
Thanks for your interest. A month or so ago, I put together a study of
ARRL Lab test data on a dozen or so contemporary rigs. My comments, and
suggestions for a handicap are based on that work. k9yc.com/TXNoise.pdf
Referring to Fig 5 in that document, we could define occupied bandwidth
at some arbitrary value of dB/re carrier. Not wanting to limit
contesters to a single radio, we might choose the TS590S at -70 dBC as a
no-penalty rig (0.96 kHz, still twice as wide as a K3), then assess a
handicap to rigs that exceed that. The FTDX5000 is ~2.6 kHz, the IC7600
and 7800 ~1.8 kHz. Althernatively, a -50 dBC value might be chosen.
The real concern here is that when the dirty signal is quite strong for
whatever reason -- competing hams nearby, big amplifier, mountaintop
location -- the dirty rig chews up much more than their fair share of
bandwidth.
How might this be verified on the air? Professional spectrum analyzers
to do this are quite expensive, and out of the range of nearly all hams.
I own two such units, a Rigol, and an HP 8590D. Neither come close to
the needed resolution bandwidth. The Elecraft P3, connected to the IF of
a radio with a sufficiently robust receiver, is quite capable of
measuring within a few dB at -50dBC with resolution bandwidth narrow
enough to clearly shows the width of signals. I'm using one with a K3. I
don't know how good the resolution bandwidth is for the new Flex
6xxx-series displays. Obviously, for any of these measurements, the
signal must be above the noise (and other signals) by at least 6 dB more
than the desired dynamic range.
I've been urging ARRL to do equivalent tests for SSB bandwidth using
pink noise as a test signal. For reasons noted in my report, pink noise
has been used as a test signal in pro audio for more than 40 years. I'm
currently pursuing this myself, and will publish if and when I've
produced anything useful.
73, Jim K9YC
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