On Tue, 15 Feb 2005 04:44:49 GMT, Larry W4CSC wrote:


Isn't it amazing how 2,000 watts of peak RF power just appears from thin
air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its
the printer stepper motor that turns the rubber band that drives the PC
board antenna array...??

Not sure about the merits of this beef.
A radar with a pulse repetition period of 1 millisecond, and a pulse
width of 1 microsecond has a peak power about a thousand times greater
than its mean power - and this is a standard feature of pulse
radars....

Brian Whatcott Altus OK

Think "watt-seconds".

2000 watts for 2 microseconds requires 4 watt-milliseconds or 0.004
watt-seconds. Throw in the PRF, and the rest is heat.

Roger

http://derbyrm.mystarband.net/default.htm

"Larry W4CSC" wrote in message
...

snip

Isn't it amazing how 2,000 watts of peak RF power just appears from thin
air for only 1-2 watts more DC? Magic? Divine intervention? Maybe its
the printer stepper motor that turns the rubber band that drives the PC
board antenna array...??

I would like to see out 8 to 10 miles with the
radome mounted 20-30' up the mizzen.

Hi Bruce,

As Jeff says, your radar will not be able to pick up small targets past
your visible horizon (about 6.3 nm according to Bowditch). You will be
able to pick up big, tall contacts further out, but that's about it.

I'd stick to a 1.5 to 2 kw radar if I were you. Higher power doesn't
"burn" through anything, including fog, and I think 4 kw is over kill
for what you'll be doing. In fact at the short ranges you'll be
operating at, the higher power will probably be a disadvantage. The
RayMarine stuff looks pretty nice and has alot of nice features (like
color and MARPA (their adaptation of ARPA)). But I'd go with a small
Furuno if you can afford it or another JRC if you're on the cheap. Just
my biased opinion though. Walk around the docks and see what the
smaller commercial fisherman in your area use. They tend to only get
stuff that works, why not do the same?

Just remember, if you get too fancy a radar, chances are your attention
will be fixated on that fancy screen and not your main navigation tool:
your "Mark I Mod II Eyeballs" ;-)

Hope this helps,

Paul

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In article ,
renewontime dot com wrote:

Higher power doesn't
"burn" through anything, including fog,

Bzzzzt, wrong answer Dude, would you like to try for what is behind
Door #3??????

When was the last time, you measured Water Adsorption at 10Ghz?
Obviously, not in the last 50 years, since Xband has come into
Marine Radar use. Water Adsoption is a Significant cause of loss of
Targets, when the humidity of the air between the transmitter
and target is high. 4Kw PPP wil certainly "Burn thru" more
humid air than 2Kw PPP. One must also consider, that heavy rain,
like in squalls, will also tend to drop the siganl level of received
targets in the Xband, due to defraction of the RF by the rain droplets.

These, and other KNOWN, physical elements all play a part in
Maximum Detection Distance of a target in Marine Radar Systems.

Me one who deals with this stuff every day......

On Mon, 14 Feb 2005 21:22:32 GMT, Me wrote:

In article ,
renewontime dot com wrote:

Higher power doesn't
"burn" through anything, including fog,

Bzzzzt, wrong answer Dude, would you like to try for what is behind
Door #3??????

When was the last time, you measured Water Adsorption at 10Ghz?
Obviously, not in the last 50 years, since Xband has come into
Marine Radar use. Water Adsoption is a Significant cause of loss of
Targets, when the humidity of the air between the transmitter
Perhaps you mean 'absorption?' 'Adsorption is hardly possible for rf.



and target is high. 4Kw PPP wil certainly "Burn thru" more
humid air than 2Kw PPP. One must also consider, that heavy rain,
like in squalls, will also tend to drop the siganl level of received
targets in the Xband, due to defraction of the RF by the rain droplets.

These, and other KNOWN, physical elements all play a part in
Maximum Detection Distance of a target in Marine Radar Systems.

Me one who deals with this stuff every day......



Rodney Myrvaagnes J36 Gjo/a


Does one child rape really change Strom Thurmond's lifetime record?
For better or worse?

On Sun, 13 Feb 2005 17:20:53 -0500, "Bruce on horizon"
wrote:

I would like to see out 8 to 10 miles with the
radome mounted 20-30' up the mizzen. I

Sidebar question: Am I woefully ignorant on radar implementation or am
I correct in assuming that a target heading directly for one's bow
would be invisible to a mizzen mounted radar due to the three-to-four
degree "screen" of the main mast directly ahead?

Or am I missing something? Why the mizzen (aside from its convenience
and the fact few people use a mizzen stays'l, so nothing to hook the
radome or mount).

R.

I am not a schill for Practical Sailor (subscription newsletter), nor
do I play one on TV, but I do find their articles generally useful,
educational and informative. They did a piece on 'Entry Level LCD
Radar' in September '04, the preamble to which you can see he

http://www.practical-sailor.com/pub/...es/5003-1.html

MW

Stay away from Raymarine! Since they separated from Raytheon, they're
turning into cheap junk. Stick with Furuno.

--


Keith
__
"Usually, terrible things that are done with the excuse that progress
requires them are not really progress at all, but just terrible things." -
Russell Baker
"Bruce on horizon" wrote in message
...
I had a JRC 1000 on my first boat and now I am restoring a 43 Endeavour
ketch and it is time to think about radars. The JRC was a nice unit but
woefully underpowered. I would like to see out 8 to 10 miles with the
radome mounted 20-30' up the mizzen. I know that the 4kw will give more
power out and thus burn thru in foggy conditions but most of the 4kw units
have the big displays. Everyone on this group knows the drill...what will
give me the biggest bang for the buck with the best reliability amd a thin
small display.
Thanks
Bruce

--
Shield Finishes and Nauticoat Marine Finish Systems
www.shieldfinishes.com