Larry,
Do you have ferite beads at both ends of all your NMEA cables? If so, do
they help?
krj

Larry W4CSC wrote:
"Wout B" wrote in
:


Hi,
Talking about "decent" multiplexers, all our NMEA multiplexers have
"automatic GPS back-up switching" (plus many other NMEA sentence
management features). Read about it he
http://brookhouseonline.com/gps_backup_switching.htm . I have
been playing with the idea to add a buzzer to warn the user when it
switches to the backup GPS. As the "no GPS data" detection is already
present, this is very simple to do. If there is sufficient interest,
we'll include it as a standard feature. If you want it NOW, we'll add
a buzzer to the present model for a small charge if you decide to buy
one. Wout
Brookhouse


I'd rather see shielded connectors so I can run shielded pair cables and RF
bypassing of all inputs to keep the HF SSB from screwing all the NMEA crap
attached to it. Shielding everything would also make it so we could HEAR
the HF receiver and get our WEFAXes without the constant drone of NMEA
radiated interference from all the unshielded, unbalanced connections with
just open wires sticking out of things. NMEA needs to get its act together
and enforce some standards on its members....

Of course, we could dump all this proprietary crap and just wire the boat
for Ethernet, negating the need for multiplexers in 1970 serial
connections. Ahhhh....addressable Ethernet instruments all speaking the
SAME language through a good $49 wireless Netgear router to the wireless
laptop in my berth....(c;

"krj" wrote in message
. ..
Larry,
Do you have ferite beads at both ends of all your NMEA cables? If so, do
they help?

Ferrite beads don't do much on HF, but all the more on VHF. But like I said
in me other replay, it's more important to terminate the wire correctly. If
you have a shield, do not use it as a signal return as with coaxial cable.
Only connect it on one side so no current can flow through the shield,
otherwise it will radiate being a perfect antenna.

Meindert

Meindert,
The problem is that all the Raymarine Seatalk cables use red for yellow
for data, red for + volts, and the shield for - volts. Saves cost of s
third wire.
krj

Meindert Sprang wrote:

"krj" wrote in message
. ..

Larry,
Do you have ferite beads at both ends of all your NMEA cables? If so, do
they help?


Ferrite beads don't do much on HF, but all the more on VHF. But like I said
in me other replay, it's more important to terminate the wire correctly. If
you have a shield, do not use it as a signal return as with coaxial cable.
Only connect it on one side so no current can flow through the shield,
otherwise it will radiate being a perfect antenna.

Meindert

"krj" wrote in message
.. .
Meindert,
The problem is that all the Raymarine Seatalk cables use red for yellow
for data, red for + volts, and the shield for - volts. Saves cost of s
third wire.
krj

I see. What you *can* do against HF interference is to run each cable 10
loops through a ferrite ring core.

Meindert

krj wrote in
:

Larry,
Do you have ferite beads at both ends of all your NMEA cables? If so, do
they help?
krj



I tried that, too. They reduce the noise, somewhat, but the open screw
terminals on the Noland multiplexer, the unbalanced lines making all the
unshielded NMEA cables into a giant transmitting antenna just bypass them
beads or clamshell ferrites so much it's nearly useless.....

I bought a new Maxtor 300 GB external portable hard drive for my system,
today, in a moment of weakness at Best Buy ($299). It came with the nicest
WELL SHIELDED USB-2 and Firewire cables with clear plastic coverings so you
can see the braided shield inside....oh, the longing for a whole boat
network like that...(c;