Under extreme contest conditions on any band, CW rules! Why
is this so? The answer is very simple...noise bandwidth. On the
low bands, noise tends to increase as you move down in frequency.
This is due to three primary reasons:
1. Local atmospheric noise (i.e. lightning storms) is propagated more
effectively on the low bands, 160 being the extreme.
2. Local manmade noise is worse on the low bands (powerline leaks,
electric fencers, and a multitude of other local sources)...again
160 being the extreme.
3. Local signal congestion interference is worse on the low bands
because you do not have the effective skip zone protection that
higher bands afford. This case is inverted on the higher bands
where most interference is from strong distant stations, but it is
more difficult to generate DX signal strengths as strong there as
commonly experienced on 160 or 80 from local stations (-20 to -30 dBm).
Because of noise, any mode which allows a smaller (i.e. narrower)
noise bandwidth will be more effective in communications than a mode
which requires larger bandwidths. W8JI recently commented on this on
the FT-1000MP reflector:
http://mailman.qth.net/pipermail/1000mp/2002-August/003416.html
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The reason is noise power is directly proportional to receiver
bandwidth, while signal level is constant as long as the signal is
narrower than the bandwidth. If you have a 100Hz filter bandwidth and
a 100Hz signal bandwidth, and switch to a wider 1kHz bandwidth, you
increase noise ten dB.
(This is most of the reason why people think PSK is significantly
better than other modes like CW. The digital system uses a ~70 Hz
filter in the computer but and the "ear" listening hears the signals
through a 2.1kHz SSB bandwidth of the receiver. Switch to a 100Hz
filter and copy a slow CW signal at slow typing speeds, and that
"apparent" advantage evaporates.)
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SSB has an advantage in contest conditions where there is
relatively low manmade or atmospheric noise (20-10 meters) and
especially where interference due to signal congestion is not an
issue (i.e. 10 meters). Where congestion interference becomes an
issue, CW again has the advantage because of its narrow noise
bandwidth. In this case, the noise is primarily due to adjacent
signals rather than atmospheric or local manmade noise. The WRTC
teams made most of their contacts on CW because signal congestion
was severe on all of the bands below 10M and their 100W signals
were most effectively heard on CW using narrower bandwidths than the
wider bandwidth SSB requires. Taking a quick glance at the results,
only ONE of the 52 teams made more contacts on SSB than CW, and the
top 5 stations made 62% of their total contacts on CW, even though
scoring incentives were identical for both modes:
http://www.wrtc2002.org/results.htm (click on Full WRTC2002 Score
sheet link at the bottom for Excel spreadsheet)
I don't believe any current digital mode has an advantage
over either CW or SSB in contest conditions, not due to any
bandwidth considerations, but simply due to the awkwardness of the
human/computer/radio interface in making contacts rapidly (tuning,
identifying, exchanging, etc.) IMHO the human brain coupled to a
radio is a far more powerful combination under contest conditions
than any mode which requires a computer for coding/decoding signals.
This might change in the future but that's how I see it today.
73, Bill W4ZV
P.S. The 2000 CQ 160 CW & SSB Contests had nearly identical
participation levels (December 2000 CQ Magazine listed 4606 unique
calls for SSB and 4512 for CW), so participation does not explain the
advantage CW demonstrated in the contest results. Also, the 2001 ARRL
bandplan was not in effect for any 160 contest results previously
referenced, so all USA SSB stations had full access to the entire band.
(Of course there WAS a bandplan in effect before 2001 but nobody honored
it until Riley Hollingsworth sent enforcement letters last September).
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