On Sat, 8 Nov 2003 20:09:43 +0100, "Meindert Sprang"
wrote:

"Larry W4CSC" wrote in message
...
The only 2400 Mhz RFI source on your boat is probably your microwave
oven at 2450 Mhz. There is no interference from 150W of HF through
the wireless.....LIKE THERE IS ON EVERY WIRE OF THE NMEA SYSTEM aboard
the boat. NMEA wiring cannot be effectively shielded as long as.....

You just take every opportunity for a rant about NMEA, don't you?

What rant? The truth is an unshielded RS-232 serial connection with
ground hooked to one side of the damned balanced line is a big
transmitter! Unshielded plastic crap has no business around an HF
receiver with any kind of a switching IC inside it.
Well....duhhhh....

I don't give a **** about your maximized profits in that plastic box.

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?

Hmm...100mbit is 100 Mhz. So, there's a carrier buzz around the upper
end of the FM band....then there's that 3rd harmonic at 300 Mhz, way
above Channel 16, as it were....well? Duhh....

Of course, the wireless network equipment is all built to FCC
SPECIFICATIONS (i.e. Type Accepted, Class B Computing Device?) and is
SHIELDED to pass?.....well, duhhhh... 2400 Mhz isn't gonna tear up
anything on our boat. Will it yours?

NONE of the plastic boxes the damned cheap marine crap comes in is
shielded in the first
place against the HF transmitter or your 5W walkie talkie on deck.

Another one: It is NOT necessary to put electronics in a shielded boax to be
EMC proof. It all depends on proper PCB layout. A lot of equipment in
plastic unshielded boxes carry FCC or CE approval. They don't get that
approval when the equipment is radiating like hell or going dead when keying
an SSB.

May we test your plastic box in the FCC Lab? I can make that
arrangement if you like..... Even if the damned thing had the most
rudimentary sprayed-on shielding like the monitor you're reading or
the computer sitting next to it, it would be an improvement. But,
then, of course, I'd want SHIELDED BALANCED WIRES in SHIELDED
CONNECTORS, next, wouldn't I.....not some damned fool screw terminals,
or worse yet spring terminals like B&G and Raymarine uses, as if we
were hooking up a student lab station in a grade school project.

You wanna SEE radiation, wait until those cheezy spring terminals
corrode against the copper wires making that great DIODE harmonic
generator! I've already found two!

Whatever happened to those nice metal, waterproof, shielded connectors
with all the wires INSIDE the shield, instead of hangin' out the end
of a cheap plastic cable with a little tab labeled NMEA (+)?


Larry W4CSC

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