Radar controversy

[Adam]

A "friend" of mine, no realy not me a friend, is about to instal a furuno radar on the aft railing on his 25D Dory. He picked this location insted of the mast because he thinks and was told that you get less artifact and interference from the mast and riging. What dose the jury think. Were is the best place to mount the radar, Mast or aft railing and why.



Adam@zazzera.com

[John Vigor]

The aft railing is a wonderful place for the radar if you need radiation therapy, or if you're aiming at sterility.

Beware. Radar emits seriously harmful radiation at close quarters.



jvigor@qwest.net

[John R.]

The aft railing is a wonderful place for the radar if you need radiation therapy, or if you're aiming at sterility.

Beware. Radar emits seriously harmful radiation at close quarters.

Absolutely, you never install a radar transmitter dome on a stern rail or any place at or near the same height as a person on a vessel. That is a major no no. A stern pole or arch is appropriate though. The later being very esthetically untasteful in my opinion. A stern pole will work very well if it is made and installed properly and places the radar dome at a safe height.

I prefer a mast mount myself as that leaves the stern available for a pole to mount a wind generator. It also locates the dome far above any crew and clear of most rigging in the forward view of the transmitter. A gimballed mount is probably better than a fixed mount but then you have to deal with the flexing and bending of the dome cable all the time and that creates premature wiring failures. The transmitter mount choice amounts to another one of those pick your poison compromise decisions to often necessary for a installation project on a boat.

I have my radar dome on the mast on a fixed platform above the spreaders. Has worked fine for many years and haven't missed any targets,............ that I'm aware of!

[Frank Vernet]

Let's look at some basic radar principles. The idea behind a radar is to detect other surface contacts and land masses as early as possible and thereby avoid them!. Therefore you want to maximize the radar's horizon range or RHR. The formula for determining RHR is fairly simple:

RHR = 1.414(sq.rt. h + sq. rt. a) where h is the antenna height and a is the target altitude below which the radar cannot illuminate the object (we'll assume zero as we are at the same altitude as our contacts of interest!). (sq.rt. is Square Root of...). RHR is in statute miles.

Example: Say one of our overpowered friends is doing 25 kts at night with no lights and the radar is mounted on the stern rail (approx. 6'). Based on the above, you can expect to detect Speed Racer at about:

1.414(sq.rt 6)= 1.414(2.45)= 3.46 miles

If, however, the radar is installed 30' up the mast, the new detection range is approx. 7.75 miles or a 124% increase in the RHR!

In addition, mounting the radar low will increase sea clutter, false returns and the cabin will probably create a 20-30 degree shadow relative to your heading.

Performance aside, I have to agree with John V. and John R. The RF emitted by these units is substantial (I keep picturing the bad guys melting like wax in the finale of the first Indiana Jones movie). You definitly want to mount the radar well above people's heads.

To all: I hope this isn't too much geekiness for the board...I know how sailors love the techie side of things...eg. max theoretical hull speed et al...

Frank Vernet
Sirius, CD33 #84

[Mark Yashinsky]

The stern rail mount is handy for cooking dinner or heating water for coffee or tea.
Adam, are you sure "your friend" didnt mean a pole going up from the stern rail??? Typical is the pole at the stern or the mast. The pole at the stern can allow a manual adjustment the the dish to compensate for heeling.

[D. Stump, Hanalei]

Adam,

I am a Radiation Protection Specialist at a commercial nuclear power station in Connecticut. Be careful were you place that antenna! Microwave radiation CAN be harmful. Want to see how harmful, try this: (NO, don't really do this, I am only kidding!!!)

First, give your cat a nice bubble bath.

Dry as much as possible with a nice terrycloth towel.

Place mostly dry cat in your microwave oven at home, set it on High for 20 minutes.

Push Start button and STAND BACK.

The microwave radiation in the oven WILL dry your cat and also cause it to BLOW UP!!!

Now, look inside the oven when cycle is complete. Imagine this is your head close to that antenna! NOT a pretty sight! By the way, the U.S. Navy has extensive procedures that must be followed when ET's are working on the Radar arrays! First procedure is: Lock It Out, Tag It Out!

Your emitter belongs as high in the rigging as you can get it. If you want to mount it at the stern, fine, just use the appropriate mounting pole to do that. Your head or body should NOT be in the microwave beam AT ALL.

One other thing, I think Edson makes a swing mount so that the emitter stays level to the surface of the ocean as the vessel heels. You might consider one of those.

I hope I don't take a beating for this, I really am only kidding about the cat. I like cats,(boiled or fried!!!)......

Dave Stump
Captain Commanding
s/v Hanalei(with a Beagle on-board!)

[Warren Stringer]

A "friend" of mine, no realy not me a friend, is about to instal a furuno radar on the aft railing on his 25D Dory. He picked this location insted of the mast because he thinks and was told that you get less artifact and interference from the mast and riging. What dose the jury think. Were is the best place to mount the radar, Mast or aft railing and why.

I think the cat in the microwave analogy is a bit overblown (VERY bad pun - intended) but I would not mount it where I would be directly exposed to the beam, either. Keep in mind that most small boat radars have a vertical beam spread of about 12-15 degrees above and below horizontal. So with a stern pole or arch mount, to keep your head out of the beam when you are standing at the helm, you probably want the unit to be 8-9 feet above you. Think about the aesthetics of this on a 25D.

Alternatives:

A self leveling mount on the backstay. These are available with the radome carried either ahead or astern of the stay, can be adjusted to the height of your choice, and take care of the heeling problem.

A mast mount, either fixed or self levelling. Here the major potential problem is fouling lines or sails when coming about.

For what it's worth, on my CD 36 we chose a fixed mast mount. We have not noticed any loss of signal directly astern. This is probably because the antenna is much wider than the mast and shoots the radar beam around it on either side.

Warren



wstringer@aristotle.net

[Warren Kaplan]

Place mostly dry cat in your microwave oven at home, set it on High for 20 minutes.

Push Start button and STAND BACK.

The microwave radiation in the oven WILL dry your cat and also cause it to BLOW UP!!!

Dave,
You may be a radiation protection specialist "theorizing" about what happens when you place a cat in a microwave oven, but when I'm not sailing I'm a veterinarian and have been for 32 years. I HAVE seen cats that some wise guy sadistic kids DID put in a microwave. They didn't blow up but why quibble about horrible effects! It sure wasn't pretty. As a matter of fact, it was down right gruesome. Now certainly radar isn't as concentrated or potent as a blast from a microwave oven set on high, or else there would be alot of "cooked captains" sailing the seven seas, but even in smaller doses it must have a cumulative effect. Put distance between the radar unit and your head. If that means putting it up the mast, prudence dictates that you do it!
Warren Kaplan
S/V Sine Qua Non



Setsail728@aol.com

[Mark Yashinsky]

Microwave "radiation" is not ionizing radation that you get from nuclear fission. Microwave energy will not give you that green glow. It is the the same energy that cell phones produce and COULD cause the same problmes that cell phones are being blamed on (the C word in the brain). Microwave energy will directly heat (local areas to a high level) items that have dipole molecules (water). Our bodies have a lot of water. What does heating areas of our bodies do to us??? I dont know, do you??? Also, do you foloow recoomendations to stand back from a microwave oven, when in use and periodically check the door seal for microwave leakage??? Do you limit cell phone usage and/or use a headset to keep the antenna away from you head???
Besides this, as was already stated, you get much better coverage, if you get the antenna up a bit.

[Larry DeMers]

Direct Microwave radiation in the eyes will cause cataracts and other problems. Higher levels of power will "cook" the recipient from the inside out..like a hot dog. I know personally of several cases in the Navy, where a tech was sent to work on the antennas, and walked in front of a microwave dish without thinking..and was killed.
The Russians have a particularly powerful radar mounted in the nose of some of their fighters. There are documented cases where the radar was turned on as the plane was taking off. People at the end of the runway got hit by the radar and were killed.

Now the power that our radars operate at is far, far less than these examples, but the effects, although proportional are the same. Do Not Expose Yourself to any radiation. Do not look into the working radome as you will expose your retinas to the radiation.

Mounting the radome on a stern rail has got to be the most foolish thing I have read of in a long time. Has this person not looked about himself and seen how others mount their antennae? Jeesh...sounds like a Darwinian award candidate to me.

Personally, I use a stern monted pole for the radome, and it works great. I am most interested in the short range performance, as that is when I need information about "hard things" the most..following channel markers through a channel, looking for the marina entrance in fog, trying to find the opening in a rocky shoreline, to a anchorage that is landlocked and hidden etc. Rarely do we use the radar at a range of more than 3 miles. Only when crossing Superior do I use the long range..and we generally see the ships visually about the same time we see them on radar, especially at night, as they light up like a city afloat. My nominally rated 16 mile radar seems to have an effective max. range of 12 miles when mounted on the stern pole. I would argue that this is more than sufficient for most requirements.

Cheers!

Larry DeMers
s/v DeLaMer
Cape Dory 30

Microwave "radiation" is not ionizing radation that you get from nuclear fission. Microwave energy will not give you that green glow. It is the the same energy that cell phones produce and COULD cause the same problmes that cell phones are being blamed on (the C word in the brain). Microwave energy will directly heat (local areas to a high level) items that have dipole molecules (water). Our bodies have a lot of water. What does heating areas of our bodies do to us??? I dont know, do you??? Also, do you foloow recoomendations to stand back from a microwave oven, when in use and periodically check the door seal for microwave leakage??? Do you limit cell phone usage and/or use a headset to keep the antenna away from you head???
Besides this, as was already stated, you get much better coverage, if you get the antenna up a bit.

demers@sgi.com

[D. Stump, Hanaslei]

Warren,

Uh, OK, maybe not BLOW UP, but not pretty(actually depends on how fast a cat boils!). WHY would ANYONE put a cat in a microwave oven??? If I had a kid that did that he would be mast headed for a LONG time!

Oh, if you are wondering why YOU don't cook when you stand in front of your microwave while it is operating, look at it next time you are using it. When you look through the window, you will see a mesh screen. The holes in the screen are at the same frequency as the microwave radiation, and that radiation will not pass through the screen! Neat, huh? If it could get through, it might stop your clock, if you had a cardiac pacemaker installed.

You know, sometimes all it takes is common sense, and I guess that's what this is all about...I remain....

Dave Stump
Captain Commanding
s/v Hanalei(NO cats on board, only a NAUTICAL Beagel!)

[D. Stump, Hanalei]

Mark,

Yes, ionizing radiation does occur with nuclear fission, but it is NOT what causes the "Green Glow". That is caused by neutron radiation that has caused "activation" of the material through which it passes.

A while ago, 3 Japanese workers assembled a critical mass in front of themselves while reprocessing spent nuclear fuel. They suffered massive radiation exposure , and two died last I had heard. In all probability, they probably saw the green flash! The green flash does not occur in the air around them, it actually occurs in the vitreous humor of the eye ball. This material contains a lot of water, and a particulate radiation passing through water at greater than the speed of light through water will cause the electrons in surronding atoms to snap temporairly to a higher energy state. When the electrons release this energy and return to their initial stable state, they will release energy in the visible light spectrum! This is called Cherenkov Radiation and IS the GREEN glow that we all hear so much about.

Ah, come on, let's go sailing, I do this all week.......

Dave Stump
Captain Commanding
s/v Hanalei

[Larry DeMers]

Most radar rcvr's have a null zone built into the circuit. This is a delay that prevents the rcvr from even seeing the area within a few inches of the rcvr, so the echo from the mast is ignored (or it would swamp out everything else coming behind it due to it's strength). On our 16 mile Ratheon radar, the closest I can see something is probably 5-10 ft. away..but it just shows up as a blob in the center of the display..

The only problem with a mast mounted radome, especially one mounted higher than the spreaders, is that you are sacrificing close-in range for a slightly longer range. That cone of 10-12 deg. that the radome emits will certaily hit a target 25 ft. out in front of a boat if the stern mount (either pole or the ultra expensive Questas backstay mount) option is used. But once you move that puppy up the mast, you move the cone of detection forward quite a lot..perhaps 100 ft. or more.

Now usually, the guys that want it mounted up the mast also go for more power too, thinking that they will now be able to see even better. The problem is the minimum range that these units oiperate at. The higher the power, the higher the minimum range that they can detect a bounce from. So combine the two..a high powered radome mounted high up the mast..above the spreaders for example, and you will see less of the stuff directly in front of you..the stuff that will be a problem over the next few minutes...kinda self defeating.

Another argument frequently used by those advocating higher output power and high mounted radomes is that they can see through rain easier. Well, with the narrower beam width (3 deg. vs. 6 or more on the LCD units), yes there will be an improvement in definition close up. But in practice, our 6 deg. wide beam/LCD unit can see thru moderate rainfall, fog, snow, just fine. I have tested this myself over an over, in real live use. It is all dependant on the rain and sea clutter settings. With these tools, you can remove most of the rain, and see a target in the rain..up to a point. Maybe the bigger units move this point forward a tad..but the cost differential is not worth that alone.

Cheers!

Larry DeMers
s/v DeLaMer
Cape Dory 30

A "friend" of mine, no realy not me a friend, is about to instal a furuno radar on the aft railing on his 25D Dory. He picked this location insted of the mast because he thinks and was told that you get less artifact and interference from the mast and riging. What dose the jury think. Were is the best place to mount the radar, Mast or aft railing and why.

I think the cat in the microwave analogy is a bit overblown (VERY bad pun - intended) but I would not mount it where I would be directly exposed to the beam, either. Keep in mind that most small boat radars have a vertical beam spread of about 12-15 degrees above and below horizontal. So with a stern pole or arch mount, to keep your head out of the beam when you are standing at the helm, you probably want the unit to be 8-9 feet above you. Think about the aesthetics of this on a 25D.

Alternatives:

A self leveling mount on the backstay. These are available with the radome carried either ahead or astern of the stay, can be adjusted to the height of your choice, and take care of the heeling problem.

A mast mount, either fixed or self levelling. Here the major potential problem is fouling lines or sails when coming about.

For what it's worth, on my CD 36 we chose a fixed mast mount. We have not noticed any loss of signal directly astern. This is probably because the antenna is much wider than the mast and shoots the radar beam around it on either side.

Warren

demers@sgi.com

[Olli Wendelin]

Microwave ovens in the Navy buildings where I work are periodically tested for microwave leakage. It is suprising how many new units fail the test and leak excessive amounts of radiation.

Did you ever notice the signs that prohibit pacemaker users from entering public areas where microwave ovens are used. They all leak to some extent, as do cell phones and radars, in all directions.

The amount of leakage has been deemed "acceptable" for public use. Of course in 10 years congress will probably decide to reduce "acceptable" by 90% based on "new" data.

I'll stay ahead of the curve and maximize my distance from radomes, microwaves, and cell phones.

Olli Wendelin
BLUE MOON
Charleston, SC



wendelin@spawar.navy.mil

[Frank Vernet]

Dave,

Stop it already! I'm getting flashbacks of my 6 months at NAVNUCPWRSCOL at NTC Orlando back in 1978...I'm that close to curling up in a fetal position on the floor.

I agree w/ you...let's go sailing.

Frank Vernet
Sirius CD33