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    Re: Lights etc.
    From: Brooke Clarke
    Date: 2003 Oct 10, 18:26 -0700

    Hi Peter:
    
    Adding Al foil inside a conductive mast is a waste of time.
    
    I think that the different and varied results when using commercial
    radar reflectors comes about because of the frequency of the radar.  The
    reflector is designed to work over some range of frequencies
    (wavelengths) and outside this range may not do any good.
    
    During W.W. II "Window" if you're from the UK or "Chaff" for the U.S.
    (forget the German term) was used to generate large radar returns.  It's
    made by cutting some conductive material (Al foil works) to 1/2
    wavelength.  So if you know the frequency of a ships radar then you
    could compute the wavelength (WLmeters = 300 / frequency MHz) and divide
    that by 2.  Cut some wire to that length and tie it so some insulating
    line and hoist it up.  You can see that if there's different ships with
    different radar frequencies you need a number of different "Chaff" devices.
    
    have fun,
    
    Brooke Clarke, N6GCE
    
    
    Peter Fogg wrote:
    
    >On the poor radar signal offered by yachts, with and without an external
    >reflector:
    >
    >I've heard that one of the most effective ways of improving the signal
    >return is to stuff the mast with balled-up aluminium 'paper' sold for
    >cooking purposes, that it works better than an add-on reflector which is a
    >clumsy thing to have hoisted aloft. Why it should be so I know not, as the
    >mast is usually made of aluminium anyway. An added advantage is the material
    >stops the halyards clanking inside the mast while the boat rocks on its
    >mooring.
    >
    >There is also an electronic device that amplifies the radar signal before
    >returning it so the vessel using radar gets a signal that looks like an
    >aircraft carrier, thus difficult to miss, and another with an adjustable
    >audible alarm that warns of an incoming radar signal - a boon to solo
    >sailors.
    >
    >
    >
    >
    
    
    

       
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