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Time for some help. I have a Northstar 951 xd that interferes with my Icom M120 VHF. In particular, whenever the 951 XD is powerred on, the display on the VHF acts as though it is transmitting (ie the bars ). After several telephone calls to Northstar, they suggest it is RF noise being picked up by the VHF from the DISPLAY of the Northstar (not any of the wires). Short of sending the Northstar back to Northstar, (done that been there no relief), does anyone have any ideas other than putting more space between the two units (not feasible sine they are both flush mounted). Here is what I have done to try to fix the problem--none has worked:
1. VHF wired directly to battery
2.Ferrite beads on Northstar and Icom
3.Ground Northstar and VHF chassis
4.separate antenna leads for Northstar and VHF
Any help would be greatly appreciated.
It looks like the radiation originates directly from the 951 screen. You may try the following just to see if it works;
1) Get a piece of copper screen about one foot square. Get a clip lead and clip it on to the copper, then clip the other end of the clip lead onto a good ground or the metal chassis of the 951, which you said is already grounded.
2) Pull the radio out of it's flush mounting but leave all of the wires intact so you can turn it on.
3) With both the 951 and VHF on, kinda wrap the copper screen around the the VHF, especially the VHF screen.
4) Then try covering the 951 display with the copper screen. Then wrap the copper screen totally around the 951.
The point of all of the above is to find out if a metal grounded barrier between the two units and properly placed will block the screen radiation from the 951. Does the 951 have a CRT display?? If so, you may never be able to block the radiation. I had an old CRT Depth Sounder that radiated into everything. Finally had to junk it.
Gil thanks. I do not think that the 951 has a crt display but I am not sure. Assuming I do all you say and it works, how would I adapt that solution to my actual usage?
Damned if I know. Dink around with the screen, maybe 2 of them, one for each unit and see what seems to work. With my old noisey depth sounder, wrapping the screen around the body of the unit seemed to work the best, but it still did not block all of the noise. Also, it was bracket mounted on the top of the console and the screen wrapped around it was not a pretty picture.
Since both of your units are flush mounted, grounded screens around both units and held with ty-wraps is not near as ugly. See what works before making decisions.
Gil - I simply pulled the GPS and sent it off to Northstar. I did not get to check with the screening primarily because the wires to the GPS were too short to permit much playing. Northstar says that it is 50-50 that they can cure a sheilding problem --if that is it. At least I'll get them to replace the memory battery. Frankly, if that does not work, I have been told that the color units (952's) should not put out RF noise. I may have to bite the bullet and get rid of the 951 XD and spring for the 952. Hate to do it just for noise but it knocks the heck out of both of my VHF's. Even f I went with a remote mounted VHF, the antenna feed for the remote VHF still comes down in the same proximity to the GPS antennae. I'm surprised that I am the only one with this issue since there are a lot of Northstar's out there as well as Icom VHF's. Any one else run into RF noise from a Northstar?
Northstar GPS Interferes with VHF 
