In article ,
"bushman" wrote:

How much does the mast effect the picture when the radar is mounted on the
stern?
How big of a slice does the mast block when the radar is mounted to the
mast?
Dang that's two questions.
- Allen
Endeavour 37 sloop
about 22' to mast 8" cross section
budget radar unit undetermined.



Ok, I like the "Pencil - Eyeball" analogy, but you need to take
into account the Wavelength of the Radar and the Horizontal
Beamwidth of the Antenna.

Small noncommercial Marine Radars will have H. Beamwidths of say
5 or more degrees. This means that this radar can't really
differentiate Targets at the same range that are within 5 degrees of
each other. It also means that your mast shadows and reflects SOME
Transmitted Energy whenever the antenna is within +/- 2.5 Degrees
of the Mast and other Conducting Rigging. Now if the obstruction
is Multiple Wavelengths wide, it will present a much bigger obstruction
and loss of Transmitted Energy, by reflection, as well as a resulting
loss of Receive Sensivity in that direction. Since 99% of Marine Radars
in the Small Vessel Catagory, are XBand, Wavelength, is 3 cm. So if
your mast is more than 12cm wide is presents a measuable loss, or
shadow, in that specific direction.

Typically, targets within 4 miles, of ANY 3Kw or higher power, Marine
XBand Radar have a much higher SNR (Signal to Noise Ratio) than
what is considered the minimum required to paint a target. This
Means that it can stand a significant loss of transmitted power and
receive sensitivity and still paint a target in the directrion of the
obstruction. Where things get dicey, is when you trying to paint
a bouy out at the horizon, that has minimal Radar Crosssection, and the
mast is in the way.

Bruce in alaska
--
add a 2 before @