Radar question

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Beflyguy

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C Dory Year
2009
C Dory Model
255 Tomcat
Vessel Name
Seven Please
After installing a new radar, there seems to be some kind of false images aft that are pretty much always there. I assume this is caused by the post for the anchor light or the GPS receiver but I'm not sure if I just need to raise the GPS or if the 1" diameter post will still cause a problem. Any opinions on this?



Radar.jpg


Neah_Bay.jpg
 
You might try reducing the gain of your receiver/chartplotter. It would be unusual for a commercially designed setup like your picture shows to create so much interference. Do you see similar false returns from large targets such as slab sided steel ships, etc? Do you see your wake or wave tops in a small chop?
 
what you are seeing is the waves behind you. Your radar should tilt down in the front a little when the boat is at rest. that way when you are bow up your radar is level and showing the water in front of you at closer distance. did you install your self? did you use a shime or spacers on the back bolts? if you have then try adjusting the sea state on the radar.
 
I too was thinking of the gain/sea state settings. Your light bar is not causing that return and your unit will "see" about 25 degrees (12.5 down/12.5 up) so unless you are really pointing toward the moon the wedge does not make much difference. (Though I too have a 2 degree wedge because it just felt right).

To give you an example - my radar will paint a HIGH bridge until I am almost going under it.
 
I believe the tower has a 5 degree forward tilt. It doesn't seem to show any waves, even at Neah Bay with 4-6' swells and 3-4'chop. The ghosts seem to be always there, always aft and boats small and large show up well in any direction except the rear where they are lost in the ghosts. I haven't tried adjusting much yet, the settings are on auto but it seems to be working perfectly except to the rear so I figured there must be something that direction that is causing the problem. The GPS antenna top is about level with the top of the radar.
By the way, this is a Simrad BR24 broadband radar.

Thanks for the help.
 
A regular radar won't pick up those supports for the light and Antenna, but the broadband is a different breed, and it may be able to "see" the mounts, and not know what to do with the data it's getting back.
 
Hmmm...well the GPS receiver should never be in the radar line of sight for max effectiveness of the GPS receiver.

I would check with Simrad to see if they can suggest some tuning/configuration. The number is 800-628-4487
 
Good idea to call Simrad. Talked to Brian there and he was very helpful. He suggested I first update the software for the chart plotter and the radar.

I also asked about a randomly intermittent sounder which he suggested might be an air bubble in the transducer liquid chamber.
 
Are those patches always in the same place? Even with the boat out of the slip and away from the pilings? The patches look like piling posts lined up, or like something close, tall and moving across the signal.

Harvey
SleepyC :moon
 
hardee":2yjcfthc said:
Are those patches always in the same place? Even with the boat out of the slip and away from the pilings? The patches look like piling posts lined up, or like something close, tall and moving across the signal.

Harvey
SleepyC :moon
Click to expand...

The patches are always in the same place, even in the garage.
 
I wonder if that could be coupler noise since it stays in the same relationship with the rotation. My first impression was that of a beacon, but the garage thing has me with a bunch of ?????s.

What is the relationship with a change of range? Does the display change positioning?

Art
 
Looks like waves to me as well. Our 16 has it's tipsy days on the water and shows waves blinking in and out with the Garmin.
 
Unbolt the radar antenna, rotate it 90 degrees, and reattach. Then turn on the radar, and see if the pattern is still shown to the aft on the display screen (namely, at 180 degrees), or if it now shows at 90 or 270 degrees. Then put the antenna back to it's original position, and rebolt.

If the pattern still showed to the aft, you've eliminated the gps/anchor masts and antennae as a source of the problem. If not, try turning the anchor lights and gps on and off (kill all power to each, which might require pulling the fuse for the gps), and see if that makes any difference in the patterns. If so, you've identified the source. If turning them on and off doesn't matter, I have one more idea.

Since the pattern shows while the boat is out of the water, it doesn't seem like there's much point in considering wakes, or other water effects, as a possible source.

Let us know what happens.
 
Following the above advice, I unbolted the radar dome and rotated it a few degrees. The ghosts seemed to turn as I rotated the thing so I concluded that the mast for the GPS and anchor light was causing the problem.
I removed the mast and built a base for the antenna and mounted the anchor light on top of the dome. No more ghosts! I don't know if this issue is exclusive to the broadband radar, but it seems to work beautifully now.

New_mount.jpg
 
Glad the ghost problem is solved. I like the new anchor light location on top of the radar dome. I'm in the process of doing the same thing, although my dome is a little too flexible for the heavier light fixture that I'm using, so the attachment will be on the "semi" vertical face, rather than the top. Looks like you're using the lighter weight plastic light, which is my next step if the vertical mounting doesn't work out.
 
Yeah, me too. I've got the GPS above the Radar on a pedestal with an aluminum mast about 6" from the radome. Have not seen the problem. It's a 4KW Raymarine.

Closeup_of_new_Radar.sized.jpg

Charlie
 
I would say Lowrance/SimRad/et al needs to look at that closely. If a mast that close to the antenna generates that type of target, then there is a high probabilty that a real target to the left or right of the mast would me missed. There has to be some way to blank a one or two degree area of the radar equating to the width of the mast to eliminate that echo. Some installations may not have the ability to move the mast.
 
tpbrady":1cmdrgqt said:
I would say Lowrance/SimRad/et al needs to look at that closely. If a mast that close to the antenna generates that type of target, then there is a high probabilty that a real target to the left or right of the mast would me missed. There has to be some way to blank a one or two degree area of the radar equating to the width of the mast to eliminate that echo. Some installations may not have the ability to move the mast.
Click to expand...

Hi Tom,

I did not try to adjust any settings at all to eliminate the ghosts. My logic in this was that I didn't want to inhibit the definition or sensitivity or limit visibility to any area even aft, if the ghosts were caused by an external mast or other target. I know that some masts, etc cannot be moved and that other solutions would have to be found. I assume there would be alternatives in this case.
 
Interesting--since conventional wave guide radar would not have caused that interference--even aluminum masts don't on sailboats.

What I am concerned about in your set up, is that it looks as if the GPS antenna is both in the beam of the radar--and is being shadowed by the radar dome--the dome itself is not an issue, but the metal part of the rotating bar is. Lowrance (Navico?) products are very susceptable to radar waves, and many of them have burned out the antennas. I am not sure if Simrad is using the same antenna--but it is very possible. If the antenna is within several feet of the radar, or within a 30 degree beam of the radar, I would move it.
 
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