? Good points, Jan E.. Does 0.91 db (1850w vs. 1500w, <1/6 S-unit)
more output really make a difference on HF when QSB is running around 3
S-units?. Some folks on AMPS have argued that it does. I am not
convinced.
I'll naively assume that this is just an academic question -- 1850W PEP
output exceeds the maximum legal limit permitted to amateur radio operators
on HF. Of course, none of us should be running more than the legal limit,
right? It might be politically incorrect to say this on AMPS, but IMHO,
contest and DX operators who do so are cheating. QRO ops who do it for
ragchewing get no respect from me, either. All of these folks ought to spend
more time working on better antennas. That's where the FCC gives us a free
pass to increase ERP on HF. It's fun to make amps that can output more than
1500W, and perhaps that's a good idea so that the tubes can loaf along at
the legal limit, but we shouldn't be transmitting at higher power levels.
As for .91 db making a difference, theory would suggest that it doesn't.
Also, I don't think I've ever heard anyone doing on-air tests in which the
difference between, say, 1150W and 1500W could be detected by the receiving
station. However, I will say that my contest run rates and success at
breaking DX pileups consistently improved when running 1500W on the 87A
versus 1000W on the SB-221. Quite often I was able to break a pileup by
switching from the SB-221 to the 87A. That's why I replaced the SB-221 with
the LK550-ZC. This sort of report may be unscientific and anecdotal, but
there are many ops who report the same thing. Maybe it's psychological,
maybe not. When you look at the theoretical gain advantage of stacked beams
versus single beams, or monobanders versus tribanders, they are actually
pretty small in terms of both dB and S-units. But there's little doubt about
which antennas do better in contests.
This reminds me of debates in high-end audio circles. Pyschology and wishful
thinking have always played big part in that arena. However, there is no
doubt in my mind that some esoteric equipment combinations actually do sound
a lot better to a trained ear. The audiophiles swear up and down that it
sounds different, while the scientifc types say the measurements show no
difference. Some of the so-called differences are purely psychological
(there are lots of snake-oil salesmen out there), but some are not. I
believe this happens because we are lacking complete knowledge about how the
human ear and brain process sound, and do not have measurement techniques
that reveal exactly why it sounds better and what it is that the equipment
is doing differently.
One of the most contentious debates concerns incredibly expensive high-end
speaker cables and interconnects. After I bought a *very* good system, I
borrowed a bunch of high-end inteconnects from the local dealer. As I
recall, some of these cables cost as much as $1000 per pair! I thought this
was a joke, but I was able to hear distinct differences between different
brands of cable in their emphasis of high and low frequency signals. It was
subtle to most people, but I could hear it easily on my ribbon speakers.
Subsequent measurements of the cables revealed a 100% correlation between
what I heard and cable capacitance. Lower capacitance cables emphasized the
highs, and higher capacitance cables emphasized the lows. Evidently, the
cables were acting like audio filters. In fact, one set of very expensive
cables had mysterious sealed black boxes on one end. The capacitance of
these cables was huge compared to the other cables. They made the highs
sound mushy and made the bass sound very nice.
I also found, of course, that shorter cables had less capacitance. My system
uses an active crossover that separates the highs and lows, so I made my own
set of short interconnects for the highs using some very-low capacitance
Belden thin coax and some high quality RCA connectors. These interconnects
cost a fraction of what the high-end cables cost and made the highs sound
crisper than any of the expensive cables I borrowed. BTW, the same set of
cables used with different speakers might sound harsh. What you hear depends
on a complex combination of variables. Psychological aversion to spending
huge bucks for a two-foot pair of RCA interconnects, or something real?
.91dB may only buy a few S-units, but that can make a huge difference when
copying weak signals or when the band is noisy. Most people seem to do their
on-air tests when signals are relatively strong and the differences are
harder to detect. I think it would be more revealing to do these tests with
the very weak, almost "ESP" signals that are common in contests and DXing.
The point is, small differences can make a difference, but sometimes that's
hard to quantify scientifically. There are still some areas where the human
detector is superior to a hardware detector.
73, Dick WC1M
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