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!"

"Larry W4CSC" wrote in message
...
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.

But you only connect the shielding on the transmitting side of the cable,
right? Never connect shielding on both sides unless it is part of the data
connection. It is always better to have signal and return in a pair,
shielded by a screen that is connected on the TX side.

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.

Hold on! That cannot be right. If the NMEA source you connect to the M802
has a NMEA A (+) and a NMEA B (-) line, it is a balanced output where both
wires are 'live'. If you connect that to the BNC of the M802, which is
unbalanced (BNC is grounded), you'll effectively short circuit the NMEA B to
ground. In such a case, you only connect the NMEA A to the input and the
ground of the NMEA talker to the ground of the listener. you should leave
the NMEA B unconnected.

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.

Normally this kind of interference could be solved by looping the NMEA wires
through ringcores, effectively breaking the antenna formed by the wires.

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.

Indeed. And if the NMEA wires are longer, you can 'break' them by using
ringcores.

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.

No problem to round off the edges. I have for instance, put RC networks on
the NMEA outputs. You can see the round-offs but a UART samples the signal
on several (mostly 16) positions within one bit time. So slow slopes on the
signal are no problem. It's not egde-driven but level driven.

Meindert

On Mon, 10 Nov 2003 15:01:06 +0100, "Meindert Sprang"
wrote:

"Larry W4CSC" wrote in message
...
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.

But you only connect the shielding on the transmitting side of the cable,
right? Never connect shielding on both sides unless it is part of the data
connection. It is always better to have signal and return in a pair,
shielded by a screen that is connected on the TX side.

It's all connected as a Faraday shield on one end only. Sure wish it
were foil coax in a sealed environment, dammit. This open crap around
screws eats my shorts.

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.

Hold on! That cannot be right. If the NMEA source you connect to the M802
has a NMEA A (+) and a NMEA B (-) line, it is a balanced output where both
wires are 'live'. If you connect that to the BNC of the M802, which is
unbalanced (BNC is grounded), you'll effectively short circuit the NMEA B to
ground. In such a case, you only connect the NMEA A to the input and the
ground of the NMEA talker to the ground of the listener. you should leave
the NMEA B unconnected.

Won't work unless you connect the coax shield of the BNC connector
(radio ground) to the NMEA -. This is EXACTLY what I'm talking about!
MANY of the instruments you buy has NO BALANCED NMEA lines! The
RL70CRC NMEA inputs are balanced lines....The Garmin are not. The
Icom is not. NMEA (-) B input to the VHF is grounded hard inside the
box. It's input is unbalanced, too. Yeoman's input and output is
unbalanced, as is the B&G Network instruments. None of these have a
real NMEA (-) and will NOT read data hooked from NMEA + to
screen/shield/ground, from the multiplexer or any balanced NMEA
transmitter source hooked up independently. You can't connect it if
IT AIN'T THERE!....

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.

Normally this kind of interference could be solved by looping the NMEA wires
through ringcores, effectively breaking the antenna formed by the wires.

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.

Indeed. And if the NMEA wires are longer, you can 'break' them by using
ringcores.

Oh, boy, let's patch it......screw that. Let's fix the manufacturing
problems and STANDARDIZE!

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.

No problem to round off the edges. I have for instance, put RC networks on
the NMEA outputs. You can see the round-offs but a UART samples the signal
on several (mostly 16) positions within one bit time. So slow slopes on the
signal are no problem. It's not egde-driven but level driven.

Meindert


I gave up trying to make it quiet. I got it lowered a bit in
strength, but it's still buzzing away like a cheap SCR light control
all over the place........

If there's a REAL emergency I HAVE to hear, I'll just shut it down and
use the radio in PEACE.



Larry W4CSC

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