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  1. #11

    Re: Can the radar see through the flybridge?

    I just wanted to note, most commercial RADOMES, and military ones for that matter are constructed from fiberglass mixed with other non reflective materials. I can tell you from personal experience, fiberglass boats can be difficult to see when attempting target acquisition because they have such a low RADAR cross section (RCS). Typically the primary return comes from other metallic structures (i.e. Engines, T-Top Support, Antennas, Metallic Paint Etc). Drug smugglers have gotten keen to this fact, and have gone to great lengths to reduce the RCS, that we are now often forced to track them by observing the wake of the vessel. This of course requires fancy processing, which is another topic in its entirety.

    For this reason, RADAR can typically "See" through fiberglass. What becomes problematic is if there are other metallic or reflective material inside of the fiberglass structure which your are trying to "See" through. I can also imagine a scenario where moisture trapped in fiberglass could cause issues too.

    With regards to safe distances from the RADAR, there are many variables which delineate this. These typically include EIRP (I would go with Worse Case), Beam width, Free space Path Loss, and Frequency. Using some pretty straight forward equations, one can calculate what the minimum safe distance should be from the array. That being said, virtually all the manuals from RADAR manufacturers address what is acceptable and safe.

    Another item I would be cautious about is the term "blanking". Typically blanking takes place in processing (i.e. video blanking). Just because you see no returns in the video does not mean the transmitter is not longer turned on when the array is pointed towards you, or to the aft of the vessel. The term I typically use is sector scan, which typically works as follows; Transmitter is turned on from 271 through 089 degree, and then is off from 090 through 270 degrees. It is entirely possible consumer RADAR manufacturers consider these two terms as synonymous, but I would double check to make sure you are not getting a false impression the RADAR is in fact not transmitting in your general direction.

    Quote Originally Posted by thoward View Post
    The radar does not pick up through the fiberglass. You will see 180* forward.
    Last edited by av8torrich; 07-23-2014 at 07:50 PM. Reason: Grammar

  2. #12

    Re: Can the radar see through the flybridge?

    From a furuno installation manual.


    1.38 Sector Blanking
    Administrations may require the radar to stop
    transmitting toward the bridge when it is installed
    on the foremast. Two blanking areas can be set at
    installation. No echoes appear in the blanking
    areas.

    Area of no transmission
    (no echoes appear)
    Figure 1-29 Blank areas where
    transmission is suspended


    Raymarine, garmin and others have the same warnings and setting.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  3. #13

    Re: Can the radar see through the flybridge?

    Agreed "Sector Blanking" is the same as what I call Sector Scan.


    Quote Originally Posted by Boatsb View Post
    From a furuno installation manual.


    1.38 Sector Blanking
    Administrations may require the radar to stop
    transmitting toward the bridge when it is installed
    on the foremast. Two blanking areas can be set at
    installation. No echoes appear in the blanking
    areas.

    Area of no transmission
    (no echoes appear)
    Figure 1-29 Blank areas where
    transmission is suspended


    Raymarine, garmin and others have the same warnings and setting.

  4. #14

    Re: Can the radar see through the flybridge?

    Quote Originally Posted by av8torrich View Post
    Agreed "Sector Blanking" is the same as what I call Sector Scan.
    I wonder how many experts here are wondering if they've been nuking themselves?

    This is a perfect example of why DIY is not always the best way.

    I don't give myself stitches (very often anymore) because a Dr. Does it better. I don't do my own taxes either. I pay a professional and don't worry about the cost. They're worth it.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  5. #15

    Re: Can the radar see through the flybridge?

    To be honest, you would be surprised how close you can safely get to an array. I am not recommending going out of your way to do so, but typically its feet not tens of feet. I have been working in RF and Electromagnetic's virtually all of my career. Most of us know, you get more unwanted radiation from the sun than reasonable exposure to surface search consumer RADAR.

    Installations are amazingly pretty straight forward, with a little attention to detail. While I agree it should be treated with a healthy amount of respect, I do not think it is something that needs to be feared. I think because folks cannot see this particular type of electromagnetic phenomena, people treat it like voodoo.

    Quote Originally Posted by Boatsb View Post
    I wonder how many experts here are wondering if they've been nuking themselves?

    This is a perfect example of why DIY is not always the best way.

    I don't give myself stitches (very often anymore) because a Dr. Does it better. I don't do my own taxes either. I pay a professional and don't worry about the cost. They're worth it.

  6. #16

    Re: Can the radar see through the flybridge?

    Quote Originally Posted by av8torrich View Post
    Agreed "Sector Blanking" is the same as what I call Sector Scan.
    I wonder how many experts here are wondering if they've been nuking themselves?

    This is a perfect example of why DIY is not always the best way.

    I don't give myself stitches (very often anymore) because a Dr. Does it better. I don't do my own taxes either. I pay a professional and don't worry about the cost. They're worth it.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  7. #17

    Re: Can the radar see through the flybridge?

    Quote Originally Posted by av8torrich View Post
    To be honest, you would be surprised how close you can safely get to an array. I am not recommending going out of your way to do so, but typically its feet not tens of feet. I have been working in RF and Electromagnetic's virtually all of my career. Most of us know, you get more unwanted radiation from the sun than reasonable exposure to surface search consumer RADAR.

    Installations are amazingly pretty straight forward, with a little attention to detail. While I agree it should be treated with a healthy amount of respect, I do not think it is something that needs to be feared. I think because folks cannot see this particular type of electromagnetic phenomena, people treat it like voodoo.
    My example would be a simple 4K open array.

    100w/meter squared RF is measured at 55 inches or almost 6 feet.
    10W/meter squared RF is measured at 178 inches or almost 15 feet.

    If I had to run for a few hours with a RADAR mounted right in front of the bridge 4 feet away Id be concerned.

    The point is the manufacturers have added a blanking area that you can set to not radiate humans. Every installation manual I have seen from RADARs has the warning to not shoot through people so I figure they know something about it.

    Its the same with SSB. There is a suggested distance from people to the antenna.

    When you get radiated all the time your on your boat it makes the outdoors less healthy.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  8. #18

    Re: Can the radar see through the flybridge?

    Those are, or have to be main beam power density measurements. This mean you are in the main beam. If you go back, you will note I told said a couple feet above and a couple feet below and you will be out of the main beam of RADAR. You will note there are many Raymarine 4KW HD RADAR installs on very small center console boats. In most of those cases you are not getting 6' - 15' away ever. That is because when you look at the antenna beam pattern, you will note that the power is attenuated pretty heavily a couple of degrees from main beam (-3dBm Point). It is not uncommon to see >45dBm of attenuation in less than five degree in some applications.

    With regards to SSB, I find a requirement which requires someone to stay 15' away at 2182 KHZ LSB suspect. While the output of the transceiver may be 100W (low duty cycle), the antennas which are used for this application have less that unity gain! Not only are the antennas incredibly inefficient at these frequencies but the are omni directional in nature. For most people, you would have the install the vertical array dead center of your 30' boat and walk to the bow or stern to your make a call on your radio? I don't think that makes much sense,

    Look at how the USCG installs not only RADAR, but MF GMDSS on their smaller RIB's. You will note, at all time their personal are much closer than 15' and most of the time closer than 6' to the two antennas in question.
    Last edited by av8torrich; 07-24-2014 at 05:15 AM.

  9. #19

    Re: Can the radar see through the flybridge?

    Quote Originally Posted by av8torrich View Post
    Those are, or have to be main beam power density measurements. This mean you are in the main beam. If you go back, you will note I told said a couple feet above and a couple feet below and you will be out of the main beam of RADAR. You will note there are many Raymarine 4KW HD RADAR installs on very small center console boats. In most of those cases you are not getting 6' - 15' away ever. That is because when you look at the antenna beam pattern, you will note that the power is attenuated pretty heavily a couple of degrees from main beam (-3dBm Point). It is not uncommon to see >45dBm of attenuation in less than five degree in some applications.

    With regards to SSB, I find a requirement which requires someone to stay 15' away at 2182 KHZ LSB suspect. While the output of the transceiver may be 100W (low duty cycle), the antennas which are used for this application have less that unity gain! Not only are the antennas incredibly inefficient at these frequencies but the are omni directional in nature. For most people, you would have the install the vertical array dead center of your 30' boat and walk to the bow or stern to your make a call on your radio? I don't think that makes much sense,

    Look at how the USCG installs not only RADAR, but MF GMDSS on their smaller RIB's. You will note, at all time their personal are much closer than 15' and most of the time closer than 6' to the two antennas in question.
    SS IS A PITA. We can usually get 6 to 10 foot from the antenna but not much more. The RADAR is usually above the people on the navy and coast guards boats that I've worked on.

    Blanking is only important if your in line with the scanner. If it's a foot or two above you it's pattern will go over hour head for the first 15 feet. After that the RF power drops enough to be safe.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  10. #20

    Re: Can the radar see through the flybridge?

    I found this link which I thought was pretty good:


    http://www.ybw.com/forums/showthread...lth-and-Safety

    I thought the author was able to describe the topic in a fairly straight forward manner. May be worth a review.

    Quote Originally Posted by Boatsb View Post
    SS IS A PITA. We can usually get 6 to 10 foot from the antenna but not much more. The RADAR is usually above the people on the navy and coast guards boats that I've worked on.

    Blanking is only important if your in line with the scanner. If it's a foot or two above you it's pattern will go over hour head for the first 15 feet. After that the RF power drops enough to be safe.

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