Radar Question

K

k3nlind

New member
First, let me say that you can see my changed radar/GPS installation in the photo section for Topkick.

Here is the situation. The very first time I had occasion to use the JVC radar, I turned it on and waited the 90 second countdown for it to get to ready mode. Then, following the on-screen instruction, I pressed xmit. The radar immediately sprang into action and worked flawlessly. The problem I encountered is that the instant that I pressed xmit, the GPS lost signal and now does not work. I shut down the radar and the Lowrance fish/GPS scope. I then turned the GPS back on and nothing. It will not lock to any satellites and acts as if the GPS antenna is non-functional.

I am wondering if anything I did could have caused this malfunction. The two things I can think of are that the GPS antenna is now mounted above the radar instead of below it, and the wiring for both is now being run in tandem.

As the wiring for both is shielded, I can't see that this change would cause a problem. Also, the GPS antenna is still approximately the same distance from the radar, so this makes no real sense to me.

Any thoughts you may have would be greatly appreciated.

thanx,

ken
 
being you have worked on the system the first thing I would check is the wiring. is it still connected? is it getting a signal? . Most GPS/chart plotters have a test page or diagnostic test.

also see if there is a fuse , inline or otherwise, that may have blown when you powered up the radar??
 
Does the GPS have power? Sounds like a fuze to me. It's going dark when you began to transmit Radar may be the key. It was well below the Radar beam before and well above now so I don't think you fried anything.

Let us know.

Charlie
 
I have used the GPS/fish finder many times since the change was made, so I am sure that the wiring is not a problem. The only difference is that the very first time I used the radar, at the instant I selected xmit, the GPS stopped working... receiving no satellites. The fish finder continued to work as always. There are fuses, but they are for the entire Lowrance package (GPS and finder) so they are not blown because the finder still functions. Only the GPS has quit.
 
Lawrence GPS antennas are not well shielded. Mine (lcx
-20) would dump when the Furuno radar was turned on until I moved it inside to the electronics shelf. I read about cases where units got fried.
 
If the gps antenna is near the Radar antenna, or it it's beam path, it will stop functioning. When we had this happen on a Furuno unit, we moved the GPS antenna, and everything was fine.

The fact that after the radar is off your gps is not coming back on worries me. re initialize the gps antenna, and it should work again.

Restarting may be called "Cold Start" in the menu of the system.
 
Check with Lowrance to see if there is a way to reset your GPS. (I have done this with Furuno systems). There may be a way to do it from your MFD.
 
Agree with previous post, assuming this radar isn’t the new broadband, and the GPS antenna is in the beam path, you probable fried your GPS antenna. Get a new antenna, if that works move it up or down out of the beam path. The radar can also fry your radio antenna if it’s too close to the radome.
 
My Garmin manual states, "Mount the GPS antenna at least 3 ft. away from the path of any radar beam or a VHF antenna. For radar beam avoidance, they recommend preferably 3 ft. above the the path of the beam; or less acceptable, 3 ft. below the path of the beam. This is a minimum distance. My GPS antenna has electronics built in to the unit which could be fried by a radar beam. I believe it is a preamp.

For the VHF antenna, it is away from the antenna by 3 ft.

Hopefully, if something is fried, it is the antenna circuit.

Tim & Dave Kinghorn
 
I assume that this is a Lowarance Antenna. They have a history of frying from radar. I had one fry which was on the electronics shelf inside the boat, and no way in the beam of the Radar (furuno). The newer ones ($150 or so) seem to be better. I had to replace the unit. I have another Lowarance and have used it with my radar a number of times--and no problems. But you want it wall out of the beam.
 
k3nlind":2pdnodjf said:
First, let me say that you can see my changed radar/GPS installation in the photo section for Topkick.
Click to expand...

Ken, I'm confused about something. I looked at your pictures, and it looks like this is the same gear that was working fine before you raised the the radome and elevated the GPS above it, yes? And, isn't the GPS actually farther now from the radome than it was before?

Do I have that right?

I am not an expert like those who have answered before, but it doesn't look like the GPS antenna is in the path of the beam.

So with my limited knowledge, I too would check as see if the GPS has power.
---
mike
 
I'm confused. You don't say what kind of JVC radar this is, and the pictures don't show the display, so what model is it? Is this one of their standalone radars that doesn't use a GPS?

From what you say the GPS isn't connected to the radar. The reason for that statement is that I have a JVC radar/chartplotter which has it's own GPS. I mounted the GPS unit directly in line with the radar, on the radar arch. The GPS gets illuminated by the radar once each sweep and always has worked well.

Also, I have used a GPS puck with the computer. It lays on the shelf directly underneath the radar, also illuminated every sweep. It also has never faltered.

So, if the GPS blew it's unique to this unit. Certainly as soon as you start to transmit, that radar is going to transmit RF power and with the symptoms, the GPS may be gone. I think that only a trip to a repair shop would prove that its good or bad.

Boris
 
Wow... lot's of stuff to catch up on... Sorry for the delay, but I have been ill and unable to respond until now.

Several things have occurred. Let me try to answer some of the questions. Yes the equipment (all of it) is the same as what was previously attached to the roof deck. No new equipment, just different mounting arrangement.

The radar is a JRC Radar 1500 MKII. The GPS is a Lowrance LGC 2000 GPS Receiver which displays a map on my fish/depth finder.

That should bring everything up to date as far as the various questions are concerned unless I missed something.

Now for a new piece to the puzzle. I hunted for fuses and all that I could find were good. I did this while the GPS was turned off and not functioning.

Yesterday we took another trip to the lake. I turned on the Lowrance, but not the Radar. There was the proverbial question mark on the map display indicating that the GPS was not functioning. About 30 minutes later, my wife asked if she should make our heading toward one of the fishing marks that I had entered months before. I responded that she wouldn't be able to do that because the GPS was not working. But because of the way she said it, my ears perked up and I decided to take a look. Viola, the GPS was tracking perfectly! I have no idea why, as it wasn't working just a few minutes before.

Now I am afraid to use the radar because the GPS might go out again and we use the GPS a lot more than the radar. In fact I only use the radar to keep from hitting rocks when I dock during no moon situations. Right now I have decided that if I ever need to use the radar, I will turn the GPS off first. Too bad, because I really like being able to use both as the same time in those conditions.
 
Others may correct me on this but I believe if you have a radar, some obscure regulation or another, requires you to have it on when underway. If you have an accident, may come into play with insurance.

Any one know what the "truth" is?

Charlie
 
ok Its wiring. fried parts don't unfry.. you have a loose connection somewhere. My c-80 unit is going on and off all weekend with out me touching it. A wire can be tight and not tight enough. take off and clean all connections then re-connect. its a pain but it will most likely be the problem.

I also think that you may have the power for the gps and the radar on the same connector some where. when the radar comes on it turns the gps off because of the power draw and a loose connection.
 
A couple of thoughts...

Ken, I suspect that you want to move your GPS puck either well above or well below the radar. I have both of my antennas on a 24" extension above the radome, with no problems.

Tom - I had a problem with my C80 intermittently shutting down (screaming alarms, etc.), and finally failing completely. It was usually happening after hitting a wake or chop and getting a little bounce to the boat. The problem turned out to be the Raymarine GPS antenna as the cause of the issue. I had over torqued the mount screws and cracked the antenna housing. That allowed water intrusion and who knows what else.

Hope that helps....

Steve
 
All this information is great and I sincerely appreciate the input. However, I know that there are no loose or corroded connections or wiring. The GPS does not work intermittently. It simply shuts down and stops working when the radar is activated. Actually, I can turn the radar on and the GPS continues to function. It is only when I press the transmit button of the radar that the GPS shuts down. Further, the JRC radar and the Lowrance GPS/Fish/Depth finder are separate units and are not connected to each other in any way.

I took measurements of the equipment. The radar dome is 18 inches in diameter. Before I moved it the radar dome was on a 4 inch mast and the GPS antenna was mounted about 4 inches below and 3 inches outside the radar dome circumference... approximately 5 inches apart, point-to-point. After the move, the GPS antenna is about 7 inches above and 2 inches outside the radar dome circumference... approximately 9 inches apart, point-to-point.

The only major difference that I can come up with is the lie of the wiring. Before the wiring was completely separate and now the wires use a common channel run through the radar mount to enter the cabin.

I uses the GPS today for five hours continuously displaying the water map and not a single glitch... I did not use the radar. If it were a fuse or bad connection I would have noticed it during that time.

BTW, we caught four large wipers... woo-hoo <;-)
 
Ken,

This is virtually identical to the problem I had with an LGC-2000 GPS module on an LCX 20. When it was mounted anywhere on the radar arch when I turned the radar on to transmit, the GPS would go offline. I had it beyond the distance recommended by Lowrance and it didn't matter. I moved the LGC-2000 to the equipment shelf inside the cabin and the problem went away. It worked just fine inside.
 
Thanx, Tom. That sounds like the same situation. Can you tell me did this occur many times and the GPS came back later? In other words did it happen to you more than once? I have still not attempted to run the radar again.

thanx,
 
Yes fried does not unfry, but a scrambled data set on the GPS will cause it to take from ten minutes to an hour download a fresh ephemeris to finally figure out what day and time it is and then find the position... Likely, the radar energy is being picked up the GPS antenna and the resulting voltage overload got into the GPS unit and scrambled the ephemeris data in RAM...

Move the GPS antenna off the top and put it in the cabin or down on the deck temporarily, then turn the radar on and see if it loses data... Very likely it will be fine and you will need to find a permanent mount away from the near field of the radar antenna...

denny-o
 
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