posted 12-16-2003 02:44 PM ET (US)            

You can use the range rings to see how far things are from your dock.

Could be fun for a few days, or at parties - show your guests!

If you set it up properly, or have somebody do it for you, radar is fairly easy to use and usually works by turning the switch to "On", or "Standby" then "On".

posted 12-16-2003 10:16 PM ET (US)            

I don't have radar on my whaler, however our biggest boat has radar. The important thing with radar is very crucial:

Mount it way above your head. Because I see these boats that have radars really close to them. Radars give off radiation that is very harmful to yourself (particularly to your heart). So mount it high.

Our boat is equiped with a Radar Arch, smaller boats too, but it is important to mount it on an arch if you are going to put it on the boat.

P.S. How old are you?

posted 12-17-2003 07:47 AM ET (US)            

Bugsy-
I am 17 and it will be mounted on the roof way above my head.

posted 12-17-2003 03:04 PM ET (US)            

Yeah, I'm 16, I have montauk...email me at JAZZ17BW@aol.com
:)
I'll send you some pics!

posted 12-19-2003 06:08 PM ET (US)            

A rule of thumb is 1.23 times the square root of the Antenna Height so for example: A 6 foot antenna should be able to see a contact at 3.01 miles. This is a limiting factor of RF Propagation without regard to a environmental factor like surface ducting or scattering. it is also called RADAR Line of Sight (LOS)

Range is a factor all to itself... PRF or Pulse Repetition Frequency is the Output of RADAR source. Usually measured in MHZ. The RANGE of RADAR is dependant on the Signal going out and coming back. So two way travel is a measured in YDS and is approx 81,000 yds for one way travel and 162,000 yds back to the receiver.

The Ability to see two contacts on the same bearing is a factor Pulse Width. This a factor of Antenna Shape

posted 12-19-2003 08:35 PM ET (US)            

Regarding the formula; wouldn't the effective range change, depending on the height of the object that the pulse is reflecting off of? In other words, you might spot a 6 foot high boat 3.01 (using your excellent example) away from you, but a 100' structure would be observed much farther away.

posted 12-19-2003 11:21 PM ET (US)            

Actually I only gave half the formula as I am used to it as application for Airborne Search Radars

the correct exact formula is 1.23 x Sqrt of Antenna Alt times 1.23 x Sqrt of the contact....

posted 12-20-2003 12:27 AM ET (US)            

Isn't your equation ignoring a few things. Effective range of the radar is also dependent upon:

Antenna gain
Cross Section of the target
Average power of the transmitter
Wavelength of the transmitted signal
Antenna scan rate

In a vacuum, the maximum detection range of a radar system =

4th root of

(P*G*c*A*t)/((4pi**2) * Smin)

where

P=average transmitted power
G=antenna gain
c=radar crosssection of target
A=effective area of antenna
t=time-on-target. Also could be pulsewidth if P is the Peak power instead of the average power.
Smin=minimum detectable signal of radar. This is based on the system's signal-to-noise ratio

Pulsewidth is the duration of a radar's transmitted pulse. It's the distance between the leading and trailing edges of the pulse as it travels through space and it's a function of the transmitter.

Notice that the detection range increases at a rate of 1/4 the amount that transmit power is increased. So, a 2000W system is NOT going to have double the range of a 1000W system.

Outside of a vacuum, in the real world, the range is decreased by the atmosphere, the target not being centered in the transmitted beam and by the fact that the some of the reflected returns are not from the center of the transmitted beam.

The "target not being centered in the transmitted beam" can be an issue if the radar antenna is mounted too high. The bottom portion of the transmitted beam might be causing target returns and those returns will be weaker than if the main part of the beam had hit the target.

posted 12-20-2003 08:29 AM ET (US)            

The Funcionality of RADAR is actually dependant on the PRF or Pulse Repetition Frequency. Certain Radar Frequencies travel farther. example an I-Band Radar (a typical Search RADAR) should always be limited by the Radar LOS.

RADAR LOS is the THEORETICAL RANGE of that radar based on antenna height and Contact.

Radar Cross section had little to do with range. Either a contact will reflect RF energy Back or it will not.

Pulse Width is a function of a RADAR beam going out and decerning two contacts on a same line of bearing at different ranges.

Range Resolution is to determine two contacts on same range at different bearings.

There are volumes written on Radar Theory, my lessons taught to me in the Navy are for Aviation Anti-Submarine Search Radars, primarily the LN-66 Made by Marconi. Great Radar!

posted 12-21-2003 08:19 AM ET (US)            

On the Aircraft Carrier I served on in the Arabian Gulf, our Radar in Operations could not usually pick up the Iranian Boghammers or Whalers. (yes the Iranian Islamic Republican Guard uses Whalers) BUT the Commanding Officer had a Faruno on the bridge, and they could pick them up. Not so much the boat itself but the Wake caused by the fast movers and the Sea Return showing up on a wake.

posted 12-21-2003 11:01 PM ET (US)            

My radar arch will place my antennae about 7' above the water. Given that limitation, is there any reason to look for radar designed to be effective at 24 miles?

JRC makes a 1000 series and a 1500 series. The main difference between the two units is the peak signal strength, but both are supposed to be more than adequate at ranges of 8-10 miles. (Actually, the theoretical range is 16 miles, but the less powerful unit probably isn't "seeing" much at that range.) It sounds like my low antennae height will limit me to more like 6-8 miles regardless of which unit I buy (assuming I'm trying to pick our small craft.) What do you think?

posted 12-22-2003 09:14 AM ET (US)            

your question requires two answers.

first of all assuming that your Antenna Heigth is 7th feet your Radar Horizon or Line of sight is only 3.25 Miles. This is a factor of physical location of antenna. Not neccessarily what you really see regarding ranges.

Assuming your Radar Antenna is a rotating antenna and if it has a slow RPM setting, I think 12 miles is a reasonable range to expect from your radar set. 12 Miles is also the rule of thumb for visual horizon and curviture of the earth at mean sea level.

A few factors I have not really touched on are the environmentals that effect Radar signals. There is always ducting that occurs near surface. This is a factor of Moisture and particles suspended in the air or whatever transmission medium you use. It is not uncommon to see extended ranges at the surface on a radar display out to 48 and even 150 miles... this is based on ducting that produces a sound channel for the radar wave to bounce off... A example is AM radio stations on a cloudy night... some times you can receive AM signals hundreds and thousands of miles away due to the surface ducting.

Short answer... yes your surface radar ranges should be reasonable to ranges of 8-24 miles.

Keep in mind Operator proficiency is also critical and you will need to practice with a sea return, high and low RPM's (will change your PRF as they rquire a different and varying frequency at different RPM) and background noise (like clouds, rain, shoreline, jetties and the like)

Hope this helps.

posted 12-22-2003 10:15 AM ET (US)            

Your effective detection range will be the sum (plus, not times as indicated above) of these two distances.

So, with a 7 foot high antenna (3.25 mile radar horizon), you should be able to pick up:

* a 7 foot high target like another boat at 6.5 miles (3.25 + 3.25).

* a 50 foot high target (lighthouse, small ship, etc.) at 11.9 miles (3.2 miles + 8.7 miles).

David

posted 12-22-2003 10:21 AM ET (US)            

Thanks for correcting my bearing drift. I thought I put plus, infact I erred and put times you are correct

posted 12-22-2003 12:00 PM ET (US)            

For example, a 24 mile radar will typically be able to pick up a smaller (less reflective) target at 10 miles than a 12 mile radar would, all other things (like the antenna & target heights, sea state, rail, etc.)

Then again, you have to balance this against cost, power consumption and antenna size.

I would think that in a small, maeuverable boat like a whaler, you are really mostly concerned with seeing things that are within a mile or two of your boat, assuming that you have a GPS that can tell you generally where you are and what direction you want to go. For example, GPS gets you close to the harbor entrance, radar allows you to steer between the piers once you get there. In terms of avoiding collisions with other boats or fixed objects, you really care most about what is within a few hundred yards.

posted 12-22-2003 12:00 PM ET (US)            

For example, a 24 mile radar will typically be able to pick up a smaller (less reflective) target at 10 miles than a 12 mile radar would, all other things (like the antenna & target heights, sea state, rail, etc.)

Then again, you have to balance this against cost, power consumption and antenna size.

I would think that in a small, maeuverable boat like a whaler, you are really mostly concerned with seeing things that are within a mile or two of your boat, assuming that you have a GPS that can tell you generally where you are and what direction you want to go. For example, GPS gets you close to the harbor entrance, radar allows you to steer between the piers once you get there. In terms of avoiding collisions with other boats or fixed objects, you really care most about what is within a few hundred yards.

posted 12-22-2003 12:01 PM ET (US)            

For example, a 24 mile radar will typically be able to pick up a smaller (less reflective) target at 10 miles than a 12 mile radar would, all other things (like the antenna & target heights, sea state, rail, etc.)

Then again, you have to balance this against cost, power consumption and antenna size.

I would think that in a small, maeuverable boat like a whaler, you are really mostly concerned with seeing things that are within a mile or two of your boat, assuming that you have a GPS that can tell you generally where you are and what direction you want to go. For example, GPS gets you close to the harbor entrance, radar allows you to steer between the piers once you get there. In terms of avoiding collisions with other boats or fixed objects, you really care most about what is within a few hundred yards.

posted 12-22-2003 12:01 PM ET (US)            

For example, a 24 mile radar will typically be able to pick up a smaller (less reflective) target at 10 miles than a 12 mile radar would, all other things (like the antenna & target heights, sea state, rail, etc.)

Then again, you have to balance this against cost, power consumption and antenna size.

I would think that in a small, maeuverable boat like a whaler, you are really mostly concerned with seeing things that are within a mile or two of your boat, assuming that you have a GPS that can tell you generally where you are and what direction you want to go. For example, GPS gets you close to the harbor entrance, radar allows you to steer between the piers once you get there. In terms of avoiding collisions with other boats or fixed objects, you really care most about what is within a few hundred yards.

posted 01-06-2004 12:18 PM ET (US)            

I have read this string with great interest. I however have a question that some of you more knowledgeable users of radar might be able to answer.

Considering the 3-4 mile horizion due to antenna height, would a smaller unit such as the JRC, have the power to punch thru dense fog or heavy rain at that range? Or is it still a matter of large dome (big antenna) 18" vs 12" and as the hot rodders say there is no substitute for power.

Thanks