Interferance Issues NASA Navtex/Icom M505 VHF

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I am experiencing some annoying interference on my VHF channels 80 84 and 71.

This disappears when I disconnect the NASA Navtex.

Tha Navtex is functioning ok.

Any suggestions?
 
Had the same problem a few years ago - interference with a Raymarine radio on CH80.

Sent the NASA unit back - and got it repaired OK with no more interference. It was still under warranty at the time, and NASA did not seem to think the fault was theirs!
 
Have exactly the same issue, with the same VHF and Navtex, despite various attemts at getting rid of it it persists, Antenna seperation and the whole install is to NMEA0400 standard for electronics, neither coax come close at any point and I have even used ferrites and tried a seperate 12v supply. I am on the verge of returning it as Dipper too did as it also interferes with the handheld so clearly radiating from the display.
 
Interference issues is a difficult area for which to write a definitive reply.

First you must understand the problem and then you can effect a cure.

Just 'fitting ferrite rings' or 'screening a local oscillator' might help but you really need to look to the problem with a spectrum analyser or oscilloscope, either or both. First you need to ascertain whether it is conducted, radiated or Intermodulation, or all three? :confused:

[TONGUEINCHEEKMODE] It could quite possibly be an Intermodulation Product (as you all seem to be from the east coast, Bardsey??) [/TONGUEINCHEEKMODE]

Some years ago, I helped a forum member from the Channel Isles with an interference problem which was traced to RF radiating from the front screen of a chart plotter.

If you are in the Portsmouth area, I might be able to assist as this specific type of challenge was the bread and butter work that we conducted daily in the government research laboratories where I worked for 25 years. :p


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Faraday cage

Try putting the Nasa box into a metal biscuit tin to see if the signal is being radiated from the base unit. The biscuit tin should be earthed and it will prevent any radiated signals reaching your VHF. If the interferance stops then you can be assured that it is the Nasa base unit that is the problem.
 
Icom/NASA Radio Interference

Many thanks for all responses.

I think I will try the biscuit tin test next time I visit the boat.

Alternatively I wiil return the NASA Navtex back to NASA for their view on the problem.
 
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