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July 15th 03, 12:07 AM

(Brian Kelly) wrote in message . com...
"Carl R. Stevenson" wrote in message ...

. . . amongst NCI's membership, and it should be pointed out
that this is the norm in the rest of the world and no real harm seems to
have come from the lack of restrictive sub-band-by-mode limitations such
as
those currently embodied in the Commission's Rules."

Simply stating the facts as perceived in terms of the membership's views.
This
is NOT NCI's issue though ... though, as I have said over and over, I
*personally*
would hate to see the digital/CW sub-bands overrun by SSB.

Carl check me here but wasn't it you who advocated the abandonment of
all mode setasides in order to be able to run wall-to-wall spread
spectrum on 20M?

Read that sentence carefully:

"I *personally* would hate to see the digital/CW sub-bands overrun by
SSB."

Spread spectrum isn't SSB.

The rallying cry I recall hearing was "no setasides for legacy
modes"...

The discussion you recall, Brian, was an exchange between Carl and
either KE3Z or W1RFI (halfheimer moment has me mixing them up, but I
think it was Jon) here some years back. IIRC, Carl thought that HF
DSSS (direct-sequence spread spectrum) could be overlaid atop, say, 15
meters. His opponent pointed out that even a QRP station with a simple
antenna would lay down an increased noise level to "narrow-band" users
for miles around if that were allowed.

Some basics:

Suppose Amateur A operates a 100 watt 15 meter SSB rig into a decent
vertical. Let's say he is S9+20 dB or louder over, say, a 5 mile
radius, and his signal is 2.5 kHz wide. That is, a 2.5 kHz wide rx
picks up almost all of the signal Amateur A transmits. (Does anybody
see anything amiss with the above numbers?)

Now suppose Amateur A switches to DSSS and spreads that same 100 watts
over 250 kHz of the band. For mathematical simplicity, let's assume
the power is equally distributed over the 250 kHz, though in reality
it will drop off towards the edges and be highest in the center. A 2.5
kHz receiver will now intercept only 1% of that DSSS signal, because
it is 100 times wider than the rx passband. So the DSSS signal sounds
like noise, but its level is 20 db lower - S9. If Amateur A drops his
power to 1 watt, the noise will drop 20 dB more - to about S6.

So we have an S6 noise level within the above area over 250 kHz of the
band from ONE station running 1 watt. Spread the signal over the
entire band instead of 250 kHzand the noise level drops less than 3
dB. How much weak-signal DX you gonna work with an S5 noise level over
the entire band?

Note also that if propagation is decent, it's not unusual to hear
S9+20 dB signals from 100-watt-and-simple-antenna stations hundreds or
thousands of miles away. What if each one of those signals dumped its
own S5+ noise level on you, even though they were running 1W out?

73 de Jim, N2EY