On Mon,4/13/2015 6:53 AM, Paul O'Kane wrote:
However, the rules make no
attempt to define excessive bandwidth, and I'm not
aware of any penalties having been imposed for this
reason alone. If I'm wrong, I'd be happy to be
corrected.
I'm guessing that this is for the same reason that the FCC Rules are
written more or less the same -- the minimum bandwidth required for the
means of transmission. That allows for progression of the state of the
art, and measurements by ARRL Labs show that the current leader for CW
cleanliness is the Elecraft K3.
This, then, defines the minimum bandwidth required for transmission.
Second in line seems to be the Kenwood TS590. ICOM's and Yaesu's big
boats using keying that burns at least twice the bandwidth, and this
after Yaesu's recent firmware upgrade. Before that it was four times wider.
Further, those numbers assume the user has selected the slowest rise
time from the rig's menu system. If a faster rise time is selected,
occupied bandwidth increases.
I've found that I can make measurements with about 75 dB of dynamic
range and very high frequency resolution with a P3/SVGA connected to a
K3 as long as I take care to keep that test setup out of overload. This
test platform isn't nearly good enough to compare the best radios for
phase noise, which should be much better than 120 dB below the signal,
but it IS good enough to yield good data down to at least 70 dB below
the signal with resolution of a few Hz. It's nearly 100X better than my
HP8590D!
This dynamic range can be achieved only with a dummy load and a tap
feeding the test set, but can be approached with a very strong signal on
a dead band. I used this setup to test N6TA's FTDX5000 before and after
he did the firmware upgrade. The improvement is substantial below 40 dB,
but doesn't do much above that level.
With the measurements I've done, The FTDX5000 and K3 perform quite
comparably on SSB, and I suspect we will see that with other rigs in
this class. The trash on SSB and RTTY comes from overdrive in the system
-- everything from clipping in the audio chain to IMD in the RF chain,
the use of AGC to set drive to a power amp, and failure to match power
amps carefully to the antenna. Spectral displays that provide waterfalls
clearly show splatter produced by SSB signals as horizontal lines on
splatter peaks.
I think it's long past time for those of us who can accurately observe
this stuff to be naming names and submitting that info to the contest
sponsors.
73, Jim K9YC
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