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!"

"Larry W4CSC" wrote in message
...
On Sat, 8 Nov 2003 20:09:43 +0100, "Meindert Sprang"
wrote:
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....

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

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.

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?

Nope.

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.

Yes. Tried it. 15Watts of VHF against the box didn't hurt it. We tested up
to 12V/m (that is above the required limits of IEC945) and it kept on
working.

May we test your plastic box in the FCC Lab? I can make that
arrangement if you like.....

Please be my guest.

Meindert

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!"

"Larry W4CSC" wrote in message
...
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.

Of course it all depends on the application. Certain areas just need
complete shielding where extremely low limits are required. All I am saying
is that to get something like NMEA equipment quiet and unsusceptible to HF
and VHF at reasonable levels like specified in IEC and FCC standards
applicable to that kind of equipment, it is not necessary to have everything
shielded. And I believe a lot of equipment present on the market prove this
statement.

And judging from your previous posts here in this group, the interference
problems you have had are caused by certain NMEA equipment that is
definately not FCC approved. Check the multiplexer and expander you so much
prefer: no FCC approval and well known to produce interference.

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.

I am not sidestepping the issue. I just happen to have good experience with
NMEA, without any interference on HF.

Unshielded 4800 baud data has no place around a submicrovolt HF
receiver within a few feet of its receiving antenna....

Like I said befo with properly filtered outputs, which is just mandatory
if you want to get something through the IEC of FCC tests, there will be no
problem. I mean, it is stupid to have NMEA drivers capable of running at
10Mbaud if you only have to drive 4800 baud. So with the properly
dimensioned drivers and RC networks, the slew-rate of the output datasignal
is brought back so such a low figure, that there are no significant
harmonics present over a few 100 kHz.

AS with consumer electronics, until the regulators step in to force
the manufacturers to conform to some sort of radiation standard,
nothing will change.

I don't understand what your implying here. Navigation electronics without
specific IEC945 approval falls in the same category as consumer electronics
and is therefore subject to the same EMC limits. So there ARE regulations
enforced.

But we seem to keep on disagreeing on this subject. So lets end this
discussion.

Best,
Meindert

On Sun, 9 Nov 2003 23:25:24 +0100, "Meindert Sprang"
wrote:

And judging from your previous posts here in this group, the interference
problems you have had are caused by certain NMEA equipment that is
definately not FCC approved. Check the multiplexer and expander you so much
prefer: no FCC approval and well known to produce interference.

I was waiting for this. I've bypass the Noland and it still tears up
MF-HF. If I run just the Garmin and nothing else you can hear it.
Any one of the instruments in the boat radiates into the Icom M802
quite badly. The more you turn on, the more noise there is.....

Oh, yeah, the Noland, too!....(c;



Larry W4CSC

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

"Larry W4CSC" wrote in message
...
On Sun, 9 Nov 2003 23:25:24 +0100, "Meindert Sprang"
wrote:

And judging from your previous posts here in this group, the interference
problems you have had are caused by certain NMEA equipment that is
definately not FCC approved. Check the multiplexer and expander you so
much
prefer: no FCC approval and well known to produce interference.

I was waiting for this. I've bypass the Noland and it still tears up
MF-HF. If I run just the Garmin and nothing else you can hear it.
Any one of the instruments in the boat radiates into the Icom M802
quite badly. The more you turn on, the more noise there is.....

Any chance of using ferrite ringcores on the NMEA lines to surpress it ?

Meindert

On Mon, 10 Nov 2003 07:56:03 +0100, "Meindert Sprang"
wrote:


Any chance of using ferrite ringcores on the NMEA lines to surpress it ?

Meindert


Not as long as the unbalanced lines are all exposed like they are.
Every cable from every instrument uses a Belden foil-shielded pair.
But the radiation is going to happen, anyway, because the output of
some of the instruments is unbalanced, inserting a radiating ground
inside the faraday shield. Most instruments, you have to abandon the
shield (screen connection for you UK readers) at the point where the
instrument's unshielded power cable with its dangling data lead hangs
out. There's no way to complete the shielding to the instrument.

Maybe Icom is right. Make all the NMEA connections via a coax
connector, unbalanced. M802 uses a BNC, in total abandonment of any
NMEA balanced concept. The shield of the coax to that BNC MUST be
connected to NMEA B (-) to get data on the radio's DSC display. So, I
figured RF from the transmitter's case follows this odd ground down
into the network shield and screws it all up. But that didn't pan out
because the network does the same thing with the cable to the Icom
disconnected. Lucky for me that during short SSB transmissions, the
system components just ignore the trashed data, so the users don't see
there's no NMEA data for the 20 seconds the SSB is talking. I think
this is the reason more people don't mention or notice it. The
displays just freeze until you stop talking or take a breath when the
SSB output power drops to a very low level and data stream resumes.

Oddly enough, I don't notice this malady on the Seatalk unbalanced,
unshielded part of the system. This may be because its cables are
much shorter and all the Seatalk instruments are very close together.
(RL70CRC Plus, Smart Heading Sensor, WAAS-GPS). Even the GPS receiver
built into its antenna has a very short cable because I found a great
little unused place right on top of the helm to port of the crank
handle for the main sheet traveler to put both Garmin and Raymarine
GPS antennas. Coverage through the fiberglass hardtop on the cockpit
is excellent and noone uses the antenna for a grabhandle like they did
when the antennas were initially on top of the hardtop. It's cable to
the Seatalk plastic box with European screw terminals is only about
10" long. None of the Seatalk wires are over 24", making them much
too short to fit an 8 Mhz wavelength.

Seatalk radiates, too, even on these short cables. If I shut down the
whole NMEA network and just run the RL70CRC Plus, WAAS-GPS and Smart
Heading Sensor with the NMEA cables unplugged from the RL70, I can
still hear data noise from the Seatalk across the HF bands. Someone
knows about this because none of the Seatalk harmonics is on a marine
HF channel. I only have a few in the ham bands.

It's just too bad there isn't a STANDARD everyone was FORCED to follow
that would completely eliminate this easily-fixed interference. USB
and RS-232C and RS-422 running at home don't tear up my ham station
sitting right next to the computer. I just can't believe marine
electronics cannot be built for these lofty prices that doesn't
interfere, either.

Ferrites won't stop the plastic boxes and unshielded cables with
square waves in them from radiating unless you rounded off the edges,
which would trash the data timing. The computers in the plastic boxes
also radiate. Doesn't take much to trash a submicrovolt receiver and
open its squelch. We used to have an Adler-Barbour 12V
electronic-controlled cold plate that just ATE, of all frequencies,
Channel 16 with its incessant pulsing, opening the squelch of all the
VHF receivers with a maddeningly repetitive pulsing shuusssh of the
closing squelch.....It only trashed 16, the channel you listen to
most. Drove all the helmsmen crazy until we figured out what it was
and shut it down. It's someone else's problem now. This fridge runs
off a 1-cyl engine compressor.



Larry W4CSC

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