Marine Safety alert, LED lights and VHF

[Cpt Pat]

Originally Posted by KP44

I will consult with other HAMs on this. It is interesting and antenna filters for specific frequencies or harmonics could be helpful. ...

Nope, antenna filters won't work well enough to be of any value. An antenna filter would need to have a very broad pass band to accommodate the entire marine VHF band - making the filter essentially worthless.

If the LED is radiating broadband noise into the operational radio frequencies, you can't reduce the noise with an antenna filter without also reducing the desired signals. You will de-sense your radio to prevent it from being de-sensed. The effort is futile.

The "filter" needs to be connected to the noise source (LED) - not the antenna. i.e., the LED needs to be properly designed. Modern VHF radios already have good "selectivity" (rejection of signals not on the operating frequency). If you are receiving noise, that noise is being radiated on or very near the operating frequency.

There are very quiet LEDs on the market, but until consumers become aware of the problem, and demand quiet LEDs, the manufactures will only be motivated by pride in engineering quality - which eliminates all the cheap imports and a few of the well-known brands. If it makes noise -- send it back! I've sent 5 back so far from well-know U.S. brands, ending up by process of elimination with only European brands. That's how I discovered the relationship between quiet LEDs and CE certification.

[conachair]

Originally Posted by hzcruiser

And fridges and freezers.

Not bad at VHF frequencies , this is with a danfoss getting turned on and off, no noise visible but you can see the AIS blips >


And at wfax frequencies ..

Turned off half way down the display, the noise modulates up and down on different frequencies. >

[Paul Elliott]

Originally Posted by Cpt Pat

True, but the FCC lets manufacturers "self-certify" RFI in the VHF range whereas CE requires lab tests for certification.

I used to self-certify equipment, and as I recall, even though we used our own test site and equipment, we had to submit test reports to the FCC. It's been more than a few years now, so perhaps this has changed. I suppose an unscrupulous manufacturer could submit falsified or gimmicked test data, but we certainly did our best to do it correctly.

Other gear I designed had to be sent to the FCC, along with our own test report for FCC verification, but these were Part-15 radio transmitters and not consumer product unintentional radiators.

[Paul Elliott]

Originally Posted by conachair

And at wfax frequencies ..

Turned off half way down the display, the noise modulates up and down on different frequencies. >

This is the kind of testing you can do with an uncalibrated SDR such as the SDRplay. The great thing about this technique is that it shows the interference (pretty bad, too) even if it doesn't happen to land on the radio channel you might be listening to. It may not hit that channel today, but it might tomorrow when your battery voltage or air temperature is higher or lower.

[conachair]

Another possible option to detect LED degradation of AIS might be the Opencpn VDR plugin.
Turn on the plugin, leave for 20 minutes then open the log in a spreadsheet to filter !AIVDM messages and count them. Turn on the LED and repeat, if you do this a few times and the numbers are consistently different it might flag up a problem which could be difficult to detect just looking at the signal.
Also slightly related, marinetraffic station details can be helpful to show any tropospheric effects going on >