"Roger Long" wrote in
:
Thanks Larry, you are a treasure.
(c; Aw, P'shaw....Twern't nuthin' (blush)
I think I have it straight now although I had to look carefully at the
timing of your posts since the second appeared higher in the list.
No network here. My set up is about one baby step past a pencil and a
parallel rule. The handheld GPS is wired directly to the fuse for
the depth sounder and knotlog. The GPS "Data Out" line goes directly
to the radio "Data +". The radio "Data -" goes to the ground block on
the same screw that GPS power - connects to. The radio is on a
separate fuse.
That'll work.
It sounds like I can expect to hear the GPS talking to the radio in
the background. Would it be a good idea to put a switch in the data
line near the radio so I can silence it in conditions where I am
having trouble hearing or understanding or just don't like the noise?
I would probably leave it off most of the time as I'm only wiring this
up for the cool factor and so I will have my position handy if I ever
need to call for help and don't want to have bring the GPS in from the
steering station.
No, it's not that easy. The unbalanced, unshielded NMEA serial lines
RADIATE RF noise, but mostly not high enough to bother the VHF, which is
FM and fairly immune, anyways. These unbalanced NMEA lines eat the HF.
Our Icom M802/AT-130 and insulated backstay get eaten alive. If you're
going to talk on HF, we just shut off the ELECTRONICS MASTER SWITCH and
do without until we're done using the HF, even receiving a WEFAX. The
emergency VHF (Icom M59) and Icom M802 HF are on separate circuits so we
can do this, safely, and still monitor Ch 16 at sea. Shielding it is
damned near impossible because the instruments, themselves, in their
unshielded plastic cases radiate some of it...(sigh) You won't see it on
your VHF. Running it continuously is important for safety. If the radio
has a constant stream of GPS data, and shows the lat/long properly, a
Channel 70 emergency call is simply pressing the emergency button for 5
seconds. You won't have time to fool around hooking the GPS up while the
hull is flooding or in horrendous seas. Run it all the time.
The radio data lines go to a two screw terminal block. When I
purchase a back up GPS, I will probably dedicate that one to talking
to the radio so I still have position data available if the one in the
cockpit mount goes overboard.
Any old GPS will feed the radio. Hell, I bought a Garmin GPSMAP 185 for
$12 at a thrift shop and found the improved, new GPS antenna online for
$38 to fit it. They're really cheap and first class GPS receivers
because Garmin refuses to support the proprietary chart plugs that feed
them any more, trying to dump the next generation of profit margins on
us. My Garmin looks brand new because it was always stored under its
custom face cover...which I also got in the $12 package...(c;
BTW I have a ferrite core on the GPS lead. When I install the
autopilot, I'm going to avoid tying the power supply to in in the same
convienient cable run as the GPS and lead it separately with its own
ferrite core.
All for naught. You'll never be able to stop the NMEA from radiating.
Don't waste your time on cores and tin foil.
Another question that just popped into my mind:
When flying, we were religious about making sure that all power to the
radios and instruments was turned off before starting or stopping the
engine. I use my two battery bank as a single battery (for reasons
discussed at length a couple years ago). Am I at risk of frying or
shortening the life of my simple electronic items? I've gotten away
with it for two years as have apparently many other people. Saiing
involves frequent engine starts and shut downs while navigation is in
progress so a voltage suppressor in the power supply to the
instruments would be a better solution than an avionics master switch
such as I had on the aircraft.
Here's where Lionheart shines. When I took over her electronics suite,
electrical power came from whatever was closest to whatever box needed
power. How awful. My captain is a little forgetful, so I installed a
completely separate 12VDC bus for all the equipment, except the Icom M59
emergency VHF and Icom M802 for the reason of the noise, above.
This separate power bus has a fuseblock at the helm for the helm
instrumentation, one at the nav station for the nav station radios and
instruments, one in my side of the V-berth for my computer and one in the
captain's playroom (aft cabin with sheepskins..(c
for his computer.
The bus is rated for 50A and is so fused next to the Main Electronics
Contactor behind the helm (which in the Amel is the overhead cupboard
over the galley sink by the boat's main breaker panel.) This contactor,
a continuous-duty, 150A power contactor from NAPA Auto Parts, pulls 1/4A
to run its main coil all the while the boat electronics is on. The
contactor coil runs through a nice brass marine push-pull off-on switch
to the house power bus, where the contactor also gets its main DC power
to run everything. A BRIGHT red power panel light is right next to the
push-pull switch, and makes a really nice night light for the main cabin
without ruining your night vision at sea. His Immenseness goes right by
this light on his way to the yacht club up the hatch, so instantly
notices he has left the whole electronics load running by mistake and can
push the button in to shut it all down, throughout the boat, ONE
TOUCH!...(c; We like our simplistic ideas on Lionheart.
As the electronics bus gets it power off the monstrous two-bank 660AH
main house batteries DIRECTLY and CANNOT be hooked to a A-B-Both-OFF
switch in the OFF position, it is impossible to connect it to an unloaded
alternator, putting 20somthing VDC to the expensive electronics...unless
some complete idiot has pulled the monsters out of the bilge....??
Starting the engine/alternators (it has 2) has no effect on voltage until
the charging current racing at 120A into the house beasts causes them to
rise towards being charged.
If you have the electronics hooked to the starting battery, YES DO NOT
OPERATE ANY ELECTRONICS WITH THE STARTER! Awful transient voltage spikes
are caused by inductive kick in the starter....
Larry
----
A skilled marine electronic technician/instrument metrologist available
for service to exotic shipwrecks like Titanic....(c;