I've often thought that a bit of SDR software might be able to
accomplish this. My thought was to use a sliding cursor on a spectrum
(panadapter) display to center on a particular signal, "capture" that
signal in a defined and reasonably narrow bandwidth (say 20 Hz for CW
and 2 KHz for SSB), read a wider (say 20 KHz) window around that signal
in narrow slices (maybe 20 Hz for both modes) to identify the energy
bursts that time wise track track the cursor window. It should be
possible to separate the wideband trash from other signals by comparing
the slice bursts to the average energy found in those segments when the
cursor window is "quiet". I'm not sure how short in time the windows
would need to be captured, but ideally they should be quick enough to
properly capture and quantify key clicks. I haven't totally convinced
myself this process would be feasible for SSB due to the variations and
complexity of human voice, but I think it should be quite practical for CW.
Once the spectrum was quantified, it would be possible to create a
profile of the total transmitted energy and "negative weights" could be
assigned to each analyzed segment based upon their magnitude
(proportionate to the energy in the cursor segment) and their separation
from the cursor frequency. Neither the magnitude weight nor the
separation weight need be linear factors ... they could have some kind
of logarithmic curve to more strongly penalize stronger or further
energy. Add up the segments and the result would be a "value" that
could be used to grade a signal.
The hardware required could be as simple as a Softrock feeding a decent
computer soundcard. The software would need to be written by someone
more capable than I, but to be honest, I'm surprised that someone has
not already done so. I'm pretty sure that the processing power is there
for it.
Defining "goodness" for purposes of point deduction or disqualification
is quite another matter, of course. That becomes much more subjective,
but it could be as simple as using the ratio of energy within/without a
defined bandwidth as a multiplier for scores. If 30% of your energy was
outside a predefined limit, your score might be reduced by 30%. Just
thinking out loud here ...
A useful aspect of this technique is that it could be applied to any SDR
file ... it wouldn't need to be performed in real time.
73,
Dave AB7E
On 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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