On Sun, 9 Nov 2003 10:08:42 +0100, "Meindert Sprang"
wrote:


That is nonsense. It all depends on proper PCB design. I HAVE measured it,
for crying out loud!

Gee, the manufacturers that HAVE to pass FCC specs on radiation don't
know that. They spend lots of money coating cases, using metal
cabinets, and other shielding. You should go into consulting. Organ
manufacturers would love to put out digital organs and keyboards
without having to coat the whole thing in tin foil and expensive
shielded boxes with foil shielded data lines to pass the FCC tests.

Why would NMEA at 4800 baud produce more interference than a 100mbit
network
on UTP (U=Unshielded)?

Well, duhhh.....Lemme see....we have a 4800Hz square wave...so
starting at the fundamental frequency of 4.8Khz, a square wave (just
pretend it's not data for a minute) has an odd harmonic every 4.8Khz
from 4.8Khz to....well....30 Mhz, easy?

You were talking about interference on 2400MHz, right? Apart from that, have
you ever heard of slew rate? A properly filtered 4800 baud output has
filters on it, which just cuts off any higher harmonics that can be
dangerous. So even with a single wire hooked up to the NMEA output, it can
be silent on HF.

Whoa, sport! Your attack on me was about 4800 baud NMEA and it
RADIATES LIKE HELL into the HF on every boat I know of because of the
way you manufacturers treat the interconnects, dangling the 4800 baud
pulses out there in unshielded space. Quit sidestepping the issue.
Unshielded 4800 baud data has no place around a submicrovolt HF
receiver within a few feet of its receiving antenna....


AS with consumer electronics, until the regulators step in to force
the manufacturers to conform to some sort of radiation standard,
nothing will change. We'll all still receive expensive new equipment
with data wires dangling out open to hook to the cheap terminals on
the unshielded plastic boxes......



Larry W4CSC

"Very funny, Scotty! Now, BEAM ME MY CLOTHES! KIRK OUT!"