"Larry W4CSC" wrote in message
...
I'm building an extensive NMEA network aboard "Lionheart" for its
owner who likes to have 2 of all the toys. I encountered a problem
adding a Yeoman to interface the paper charts to the network,
yesterday, that might be a good idea for everyone to know about.......

snip

Luckily, no damage was done. The Noland had simply latched to protect
itself and recycling the master power relay reset it to working again.

Has nothing to do with protecting itself. Just something that happens if you
overload an *unprotected* output on a CMOS circuit. Eventually the circuit
breaks.

big snip

Now with all the wires disconnected from my bruised NMEA network, I
put the logic probe on the Yeoman's input and output wires. YAAACK!
THE INPUT WIRES ARE HIGH.....BOTH OF THEM!! How can this be? This is
the INPUT, not the output! A reading with my DVM showed battery
voltage, 13.8V with no connection to them...both of them.

And this again proves the nessecity of galvanically isolated inputs on NMEA
devices. But many manufacturers try to save a dime and omit a cheap
optocoupler.
And it gets worse: even Noland dropped the galvanic isolation on their new
"improved" models.

commercial mode on
So, get the best multiplexers you can get: www.shipmodul.com
commercial mode off

Meindert

Larry,

Are you generally satisfied with the Noland mux? I installed one and
started having problems when the system started to scale up. It doesn't
handle saturation very well. I switched to one od Meindert's Miniplex-USB
units and have been very satisfied.

Doug

"Meindert Sprang" wrote in message
...
"Larry W4CSC" wrote in message
...
I'm building an extensive NMEA network aboard "Lionheart" for its
owner who likes to have 2 of all the toys. I encountered a problem
adding a Yeoman to interface the paper charts to the network,
yesterday, that might be a good idea for everyone to know about.......

snip

Luckily, no damage was done. The Noland had simply latched to protect
itself and recycling the master power relay reset it to working again.

Has nothing to do with protecting itself. Just something that happens if
you
overload an *unprotected* output on a CMOS circuit. Eventually the circuit
breaks.

big snip

Now with all the wires disconnected from my bruised NMEA network, I
put the logic probe on the Yeoman's input and output wires. YAAACK!
THE INPUT WIRES ARE HIGH.....BOTH OF THEM!! How can this be? This is
the INPUT, not the output! A reading with my DVM showed battery
voltage, 13.8V with no connection to them...both of them.

And this again proves the nessecity of galvanically isolated inputs on
NMEA
devices. But many manufacturers try to save a dime and omit a cheap
optocoupler.
And it gets worse: even Noland dropped the galvanic isolation on their new
"improved" models.

commercial mode on
So, get the best multiplexers you can get: www.shipmodul.com
commercial mode off

Meindert

On Mon, 29 Sep 2003 08:22:42 -0400, "Doug Dotson"
wrote:

Larry,

Are you generally satisfied with the Noland mux? I installed one and
started having problems when the system started to scale up. It doesn't
handle saturation very well. I switched to one od Meindert's Miniplex-USB
units and have been very satisfied.


First, I didn't buy it, the captain did. He had it a while before I
took over the electronics on the boat. I would have found out they
expected you to have the computer running all the time and would have
looked elsewhere. Noland's documentation sucks. I can't find
anywhere it says I have to use the TX output on the computer RS-232C
for raw NMEA output if I don't want to use the computer, but that's
how the thing works. It was made to use with The Cap'n and computer
controlling the network. I have a toggle switch to put the computer
in or out by switching between the TX terminal and the TLK terminals.
That's strike one.....

It's not shielded so it radiates all over the HF bands. Idiots.
You'd think this wasn't going into a BOAT with RADIOS. Idiots.

The TX output can only sink 15ma of current, according to what Roland
told me. Luckily, the load total I have on it is well below that, at
the moment. I'd simply add a switching transistor to boost it but
it's an aggravation and design flaw.

For these reasons, I would have looked elsewhere for a multiplexer. I
doubt I would purchase the one you have because I've borne his nasty
attitude on this newsgroup which would preclude me buying his products
even if they were perfect. Tact is one of a salesman's most important
traits.

Well, I've shielded the Noland in a budbox hooked to the shield system
and will do more of this after the whole system is up and running as
time goes by. Where we'll be operating on HF there's very little
interference, unlike the lower frequencies. Luckily, the Navtex
frequency is in between NMEA harmonics and it works fine. I haven't
monitored 500 Khz in years, but it's also noise free on the Icom.

It's all just too bad they all try to cut each other's throats and
NMEA seems powerless to cause its integration to be consistent with
good engineering practices. The shielded pair balanced line is a fine
idea.....It's just too bad most of them say to hell with it and invent
radiating systems like SeaTalk or Fastnet with unbalanced lines,
unshielded cheap plastic connectors and every place a cable hooks to a
device you're using unshielded screw terminals or cheap plastic
connectors, none of which fit anything else. How stupid they ALL are.



Larry W4CSC

3600 planes with transponders are burning 8-10 million
gallons of kerosene per hour over the USA. R-12 car air
conditioners are responsible for the ozone hole, right?

"Larry W4CSC" wrote in message
...
On Mon, 29 Sep 2003 08:22:42 -0400, "Doug Dotson"
wrote:

For these reasons, I would have looked elsewhere for a multiplexer. I
doubt I would purchase the one you have because I've borne his nasty
attitude on this newsgroup which would preclude me buying his products
even if they were perfect. Tact is one of a salesman's most important
traits.

Sorry to hear you feel that way Larry. I am not a typical salesman, I am a
technical guy that happens to sell his products to make a living. I also
like to help people out and get carried away sometimes in doing that. That
also means that I can react a bit offensive when someone explains something
to someone else and I feel the explanation is in error. But what drives me
to be like this is honesty. So if I offended you somehow, I apologize. I
just notice that you can also get carried away sometimes.... ;-)

Being on the subject, I would like to switch to salesmode again: :-) If you
want to try our multiplexers to see if they solve your interference problem,
I can arrange for you to get one on trial. If you're not happy with it, you
may return it and get a refund. Just let me know.

The shielded pair balanced line is a fine
idea.....It's just too bad most of them say to hell with it and invent
radiating systems like SeaTalk or Fastnet with unbalanced lines,
unshielded cheap plastic connectors and every place a cable hooks to a
device you're using unshielded screw terminals or cheap plastic
connectors, none of which fit anything else. How stupid they ALL are.

An unshielded multiplexer CAN be quiet on HF if designed properly. Ours also
has an unshielded box and unshielden screw terminals. But they work fine and
do not interfere on HF, nor are they susceptible to HF. We have tested them
according to IEC945, which goes up to 10V/m. No problem.

Regards,
Meindert

For these reasons, I would have looked elsewhere for a multiplexer. I
doubt I would purchase the one you have because I've borne his nasty
attitude on this newsgroup which would preclude me buying his products
even if they were perfect. Tact is one of a salesman's most important
traits.

That's a pretty unfair statement. I've had nothing but positive experiences
with
the man and the company.