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July 16th 03, 12:53 AM

(N2EY) wrote in message . com...
(Brian Kelly) wrote in message . com...
"Carl R. Stevenson" wrote in message ...

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.

Yeah, I saw it and passed. There's just so much a body has time to
"handle". SS is OK on the HF ham bands but BPL is bad. Beats me.

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

What the hell is the definition of a "legacy mode" anyway?

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.

Ayup.

Some basics:

Suppose Amateur A operates a 100 watt 15 meter SSB rig into a decent
vertical.

As an aside there is no such thing as a "decent" vertical if used
above 40M.

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?)

Nope.

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.

OR, in the cw setasides where 4-500 Hz filters are commonly used the
received energy from SS signals would be reduced by 80% vs. the case
with the 2.5 Khz ssb filter. Still ridiculous.

So we have an S6 noise level within the above area over 250 kHz of the
band from ONE station running 1 watt.

Who sez they would only run one watt and how many of 'em on the air
simultaneously would it take to (fill in the blank).

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?

Zilch. I routinely work stations which don't even flick my
oversensitive zero-inertia S-meter into the first LED segment.
Whatzzat if you believe S-meters, an SØ?? 25-30 dB weaker than the SS
signal?

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?

The band would be rendered useless for the hordes by anybody running
SS and that's why it ain't never gonna happen in our lifetimes.

73 de Jim, N2EY

w3rv