On Sun, 14 Jun 2009 16:46:51 -0400, "Wilbur Hubbard"
wrote:

wrote in message
.. .
On Sun, 14 Jun 2009 14:45:20 -0400, "Wilbur Hubbard"
wrote:

"Brian Whatcott" wrote in message
. ..
Responding to abusive, wrong-headed posts from alias-Wilbur is very much
like banging one's head against a wall for fun - but I'll do it any way.

Radar output is the transmit power from the magnetron.
This pulse lasts 1 microsecond or less, and can be repeated 1000 times
per
second. 2.2 kW power for say 1 microsecond X 1000 per second gives
AVERAGE
power of 2.2 watts - but there is the processor, the display etc., etc
so
20 to 30 watts while transmitting is in the ball park.
A coupla amps in fact.

I expect there was SOMETHING correct in alias-Wilbur's post, but I
didn't
look at it that closely.


If you aren't transmitting you aren't using radar. Doh! And, if you have
working radar you are REQUIRED by the COLREGS to have it on and
operational
at ALL TIMES that you are under way.

RULE 7
RISK OF COLISION

(a) Every vessel shall use all available means appropriate to the
prevailing circumstances and conditions to determine if risk of collision
exists. If there is any doubt such risk shall be deemed to exist.

(b) Proper use shall be made of radar equipment if fitted and
operational, including long-range scanning to obtain early warning of risk
of collision and radar plotting or equivalent systematic observation of
detected objects.

(note: proper use does not mean turning the damned thing off to conserver
your battery power!!!)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We all know manufacturers fudge their stats to make it look like their
products are not the power hogs they really are. I refuse to believe the
claim that Rube made about their radar set only using 2.1 amps. It's
obviously way understated. Hell, the LCD display alone on my laptop draws
about that much power. The power brick outputs 19 volts DC at 4.5 amps.
The
radar set is a computer, too. It has a processor and that antenna spins
inside the dome so it has a motor and motors draw lots of amperage. We all
know that.

The bottom line is my original statement stands. Radar sets for sailboats
draw way too much power to be viable unless you run your motor or a genset
all the friggin' time.

Wilbur Hubbard


I operate my RADAR in full compliance with all applicable laws and
regulations, including the ones you cite above. I have only two
sources of power for charging my batteries. One is the little
alternator in my 9.9 hp outboard. The other is a 20 watt solar panel.
I NEVER connect to shore power (Don't even carry the cable) or take
batteries ashore to charge them.

It draws what I (and the manufacturer, and the laws of physics) say it
draws.

The outboard, at IDLE keeps up with the RADAR with plenty left over to
run VHF, GPS, Wind instrument, etc.

You can't hear my outboard running at idle from 4 feet away.

I usually don't need to run the outboard at all anyway. The puny solar
panel plays catchup very nicely during days at anchor. I do run the
motor during periods of low visibility and at night to both make up
for the lower output from the solar panel, and to give me an extra
margin of safety if a dimwit in a center console comes barreling
through the fog as they often do.

I have 2 group 27 AGM batteries, and have no trouble keeping them
fully charged.




At idle your 9.9 outboard (if it's a Honda or Yamaha) puts out all of about
half and amp at maybe 12.5 volts. It will barely charge a battery at that
voltage.

Incorrect. The output of the alternator is not linear from zero to
full throttle. Both I and my Fluke say you are wrong.

Photovoltaics rated at 20 watts are lucky to put out 15 under
optimal conditions (this means cold temps and zero angle on the sun with
clear sky.) 15 watts at 15 volts which is what you need to charge a batter
is about one amp.


Incorrect, as proved by my own measurements, taken under actual
operating conditions.


You, sir, are a LIAR! Your piddling little charging system will not run your
radar for long and keep the batteries charged at the same time.


Then I guess we'll have to declare it a MIRACLE!

Actually, only YOU will have to declare it a miracle, as I am a firm
believer in science, not miracles.