Furuno Marine Radar - Manual (Page 18)

A/D Converter
The received IF signal is an analog signal. This signal
is converted to a digital signal in order to undergo
various processing in the display unit. The A/D
(Analog to Digital) converter converts analog signals
to digital signals.
Signal Processing
This section is the heart of the Radar and contains
computers, memories, and other IC’s. Extensive use of
digital techniques permits high speed processing.
Control Unit
The control unit contains various keys and controls for
adjustment of the Radar picture. Whenever a control
setting is changed the associated reaction appears
almost immediately on the display. In some Radar
designs, the control unit is separate from the display
unit.
Basic Radar Terms
Radar Resolution: Different than display
resolution, which is a measure of the pixels in an LCD
display, Radar resolution describes the Radar’s ability
to distinctly display two Radar targets which are
close to each other. Radar has two types of resolution:
range, and bearing.
Bearing resolution is a measure of the capability of
the Radar to display as separate targets the echoes
received from two targets that are at the same range
and close together. The principal factor affecting
bearing resolution is horizontal beamwidth. The
narrower the horizontal beamwidth the better the
bearing resolution.
Figure 6 - Example of
bearing resolution
Range resolution is a measure of the capability of the
Radar to display as separate pips the echoes received
from two targets that are on the same bearing and
are close together. The main factor that affects range
resolution is pulselength. A short pulselength gives
better range resolution than a long pulselength.
Figure 7 - Example of range resolution
Generally, use a short pulselength on short ranges for
better range resolution, and a long pulselength on long
ranges for longer range detection.
Beamwidth: Beamwidth is the angular width,
horizontal or vertical, of the path taken by the Radar
pulse. Horizontal beamwidth ranges from 0.75 to
5 degrees, and vertical beamwidth from 20 to 25
degrees.
Figure 8 - Example of
scanner beamwidth
Radar FAQ’s continued ...
Q: Can I cut my Radar cable to length or should I coil it and store it?
A: It is not recommended to cut your Radar cable. Find a place to hide and coil the excess. If there is no other
way to hide the cable, it can be reduced in length but this should be done by an authorized Furuno USA dealer.
If not performed correctly, cutting the cable could lead to corrosion and may result in voiding the warranty.
Adjusting the cable length will also affect the timing of the Radar. Please confirm that the timing is still correct
if any changes are made to the cable length.
Q: What are the “streaks” or “spiral lines” that sometimes show up on my Radar display?
A: If they appear intermittently and then go away, it is most likely Radar interference from other vessels
or perhaps even a second Radar aboard your own boat. Furuno Radars offer several levels of interference
rejection, or “IR”. IR is usually selectable from a menu setting. Start by applying the first level of IR and see if
the interference stops. Even if higher levels of IR are necessary, you will note very little degradation of your
Radar picture. CAUTION: Interference Rejection may suppress certain very weak targets and/or Radar signals
from RACON buoys.
Q: Will I be able to detect weather with my Furuno Radar?
A: Yes, most marine Radars will detect weather fronts. With Furuno true color Radars you will be able to see
individual weather cells at a great distance.
Q: I am purchasing a Furuno Radar system and was wondering if I would be better off with an open array
unit or a radome type of antenna unit?
A: Generally speaking, an open array Radar antenna will have better performance than a radome antenna of
comparable output power. The open array antenna focuses its output beam better then the radome, resulting in
better bearing resolution and target discrimination. This focus is best measured by the horizontal beam width
of an antenna. The smaller the horizontal beam width the better the target resolution. If you have the space, the
open array is the best choice for maximum performance.
Q: What are the benefits of upgrading from a dome antenna (closed array), to a larger, more powerful
open array antenna?
A: The larger Radar antenna has a narrower horizontal beam width. Therefore, the Radar display has better
target resolution (a sharper picture). Greater power combined with higher resolution give the operator a
better chance of detecting and separating small, weak targets at a greater distance as well as the ability to better
penetrate through fog and bad weather.
Q: I have accessed the installation menu for my Furuno Radar but cannot select heading or sweep timing
adjustments. When selected with the [ENTER] button the Radar display just beeps twice and nothing
happens. Why?
A: Heading alignment and sweep timing adjustment cannot be selected unless the Radar is in transmit mode.
Place Radar in transmit mode before accessing the Installation Menu.
Q: My Radar doesn’t pick up targets as far as it previously did. What could be the cause?
A: The most likely cause is the magnetron. Please contact your local Furuno dealer for repair information.
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