GPS/VHF Interference

Hanapa'a Time · 05-30-2003, 08:09 AM

Just got off the phone with Lowrance, seems as though I have a unique problem.
My X-15's plotter loses signal when I key the mic.(high power any channel) on my Icom M45A. All the wires are routed away from each other and power sources are separate.
Has any one else encountered this problem??
Might have to send unit back, sooo close to salmon and hali season :depressed:

Salty Dogs are a GREAT bunch, look forward to learning, meeting and contributing more

Thanks in advance, Kurt

Pilar · 05-30-2003, 08:21 AM

Kurt, are the grounds common at any point? All ground wires and especially common grounds ( Bus bar bonds to boat ground ) are vulnerable to sizing problems. A good size for the ground bond on a bus bar is #8 or #6 wire.

It sounds like a drop out due to power issues. Remember the often neglected return path from your electronics. Any corrosion inside a lug or between the lug and a bus bar can cause a high resistance path. It will work fine until the current flow gets high enough and then the voltage comes down.

When you key the mike the current draw goes way up and the plotter drops out on undervoltage because of the voltage drop on the corroded ground.

Just a theory, I've seen it before, hope it helps.

Hanapa'a Time · 05-30-2003, 09:08 AM

Thanks Pilar,

The grounds are clean.
I have even put the VHF on it's own battery to avoid voltage drop. The "status" screen shows constant voltage, but the satellite signals drop rapidly, sometimes not right away (5 sec.).

Thanks again, Kurt

DriftR · 05-30-2003, 10:48 AM

KCS,
Same problem my buddy has with his new Furuno unit and his CB. Every time he hits the mic switch lines comes across the Furuno. He added an additional zinc to the stern. Up to that point he moved his CB farther away, ran separate wiring back to the battery. Did about everything except aluminum foil on his head. When he put in that extra zinc it didn't work on Sunday when we were offshore. But yesterday he went out (choppy and windy a real bear he said) when he mic'ed his unit it worked with no visible lines on the Furuno. Go Figure. Just keep trying to isolate it or add a zinc to it as a ground. Good Luck

Hanapa'a Time · 05-30-2003, 12:01 PM

Miss B,

Thanks for the info. The GPS antenna is mounted on the upper part of my windshield across from the VHF antenna which is mounted to the gunnel. I'll try Rogers, have had good luck in the past with them. :smile:

Kurt

Miss B Haven · 05-30-2003, 11:49 PM

Do you have the GPS antenna mounted high by the business end of the VHF antenna? I've never heard of this being a problem. I have heard about mounting the GPS antenna to close to a transmitting radar.
My GPS (Raytheon w/Differential) is mounted real clost to one of my VHF anntennas but I believe it't still below the base extension.
Call Rogers Marine and discuss with them. I believe they carry Lawrance and since they do installs usually can help with issues like this. Marty Belafsky is who I usually talk to.
Good luck. :smile:

PS- Pete was having a drop out issue with his lawrance but I think it was just powering off, not losing the signal. :whazzup:

[ 05-30-2003, 12:51 PM: Message edited by: Miss B Haven ]

Hanapa'a Time · 05-31-2003, 09:41 AM

Well, after speaking with Rogers Marine, I ended up going home and moving the GPS antenna around.
With the help of a fiberglass boat brush handle I moved the antenna up and down until my signal was not disturbed.
Anything higher than 1' above the original mounting point was okay.
A two foot extension was ordered (just before closing yesterday) from Roger's. :grin:
Apparently the aluminum windshield frame is carrying enough RF to interfere with the GPS

I also checked the standing wave of the VHF antenna, which was perfect, full power on transmit and the needle didn't hardly budge on reflective test!!!
At least I won't be without my GPS for the next hali. season, :smile: now I just have to get work to cancel a meeting on Fri. the 20th

Thanks for the help, this group is GREAT

Kurt

Hanapa'a Time · 06-06-2003, 06:34 AM

Well the saga continues, even after installing the extension, the unit still loses the map screen when the VHF is keyed.

The satellite signal is NOT lost now!!!

Seems like after I fiddle with antenna, coax or power source the problem seem to go away, only to return at some point.
Sooo off to Lowrance goes the X-15, hopefully to return before hali. and salmon season.

Pete, I understand you have had some problems with your X-15.
What was the outcome and are you using VHF, if so what brand??

Thanks, I'll post the results (if any).

Kurt

Stryker · 06-06-2003, 08:24 AM

I just sent my LCX-15 MT in for repair and got it back very quickly. They just exchanged it for a new unit rather then spending time trying to repair the old one. In fact they sent a card with the unit explaining their policy of exchanging the unit with a new one to speed up repairs.

On your VHF problem I have a suggestion. Try creating a choke in the antenna coax. Wrap the coax into a circle 8� � 10�, 5 � 10 wraps and tape together. This will help bleed off reflected RF from the antenna. This reflected RF needs a place to go and sometimes it finds strange places to go. Should bleed off to the grounded side of the coax but if there is a lesser point of resistance it will take it. The choke traps the RF and helps it make the trip to the ground. Assuming the RF ground it good. Create the choke as close to the antenna as you can. Add and take away wraps to see if it helps. I have used this technique several times when installing antennas on RV�s and boats where grounds are difficult to predict.

FYI: I�m a HAM (amateur radio operator) I have built many homemade antennas and installed all type of radios and antennas.

Stryker · 06-06-2003, 08:25 AM

I just sent my LCX-15 MT in for repair and got it back very quickly. They just exchanged it for a new unit rather then spending time trying to repair the old one. In fact they sent a card with the unit explaining their policy of exchanging the unit with a new one to speed up repairs.

On your VHF problem I have a suggestion. Try creating a choke in the antenna coax. Wrap the coax into a circle 8� � 10�, 5 � 10 wraps and tape together. This will help bleed off reflected RF from the antenna. This reflected RF needs a place to go and sometimes it finds strange places to go. Should bleed off to the grounded side of the coax but if there is a lesser point of resistance it will take it. The choke traps the RF and helps it make the trip to the ground. Assuming the RF ground it good. Create the choke as close to the antenna as you can. Add and take away wraps to see if it helps. I have used this technique several times when installing antennas on RV�s and boats where grounds are difficult to predict.

FYI: I�m a HAM (amateur radio operator) I have built many homemade antennas and installed all type of radios and antennas.

Hanapa'a Time · 06-06-2003, 08:48 AM

Thanks Stryker,

Some encouraging info., on the speedy return.
My unit is more than a year old, hope repair or replacement isn't too spendy??
As for the coax, I do have the excess coiled up under the gunnel on the antenna side, my coils are tighter, 4", might have to try larger coils when my unit is returned.

Kurt

Stryker · 06-06-2003, 12:23 PM

There are several other things to try if you get the unit back and the problem comes back with it. If you want I can give you some things to do to troubleshoot the problem.
Just E-Mail me at timt@norpac.com
Good luck!!!

Hanapa'a Time · 06-25-2003, 09:18 AM

Yeah, got the X-15 back Monday, after two weeks at Lowrance. :shocked:
New unit was sent and is up and running, without a problem :grin:
Thanks for the info Stryker, I ended up using a 2' extension(no extra coax now) on the VHF antenna and a 1' on the GPS antenna(to get them away from the windshield frame).
Look out silvers, nooks and hopefully 'buts in August!!!

Kurt

Stryker · 06-26-2003, 09:27 AM

You can download an emulators to help you practice using your 15MT on your home computer. This will allow you to spend a lot of time learning the unit off the water in the comfort of your home warm and dry. I have used it and it made all the difference in my learning curve.
http://www.lowrance.com/software/PCSoftware/demos.asp

Make sure you have the latest version of the units� software (version 2.90)

Also consider the Navionics map card (retail $199.99). They are NOAA maps on one card that will make the GPS part of your unit look and feel like a real chart.
The latest version of the units� software (version 2.90) will allow the Navionics maps to display tide flow and height on the GPS among other upgrades over older versions. I am on the third version in my unit. Loading new version to the unit is simple.
http://www.navionics.com/Usa/Index.asp

Salmonator · 06-26-2003, 09:40 AM

I've been having problems on and off with my X15mt. The transducer loses signal real easy and my GPS cursor doesn't seem to track smoothly, even when zoomed in all the way. I have a feeling mine will have to go in after the summer season.

Hanapa'a Time · 06-26-2003, 10:18 AM

Stryker,

The emulator is a great feature!!!
The new unit came with the 2.9 software, as did my old one(I updated several times as they came available).
Navionics WILL be the next investment :grin: Map Create is okay, making maps is a pain and no depth contours :depressed: Just gotta convince the wife

Thanks again

Salmonator,

Lowrance was somewhat helpful and a little slow(had unit two weeks). They could not duplicate my problem, but in the end I got my unit(out of warranty) replaced , no charge.

Hope this helps, good luck,

Kurt