VHF Radio Interference

[Dougal]

I use a small laptop as a very cheap chart plotter, powered by a 12 > 20v adapter via cigar lighter socket. Gives me a 10" screen for less that £50!

The downside is that I have to turn the VHF squelch to max, in order stop the frequent VHF interference.

Anyone know a way to remove or cut down this interference?

 

[chanelyacht]

Ferrule on the power leads of both (the radio should have one on) and move the plotter further from the VHF cable run.

 

[MM5AHO]

Likely to be the power supply, a switchmode type. Get a different one, probably more expensive type. I had same problem, got an expensive power supply and solved problem. Ferrites on power leads might help. If problem is heard on vhf, its very bad. I had problem on hf only.

 

[nemodreams]

I've just had the same ( constant squelch ) caused from a cheap usb 12v charging unit.(Wilkinsons ) Took it out no problem - on no vhf !
Yet others I have used have been ok ( even pounland ! - but that fell apart when I blinked in its direction )

I have run a cheap laptop as yours on a 12v - 20/24 v convertor ( maplins unit ) with no problems.

Geoff -

 

[vyv_cox]

You may have noticed my letter on this topic in the summer edition of YM. Quite by chance I found that the reason we were unable to receive any VHF channels other than 16 was because the iPad was charging on a USB socket. Since this was a fairly expensive item bought from Force Four I would have expected it to be suitable and tested for typical leisure marine use, but no. Now I make sure any USB plugs are out when trying to receive weather forecasts.

 

[MM5AHO]

Examination of the circuit board of some of these devices (power supplies for notebooks, phones etc) reveals that many components are left off. The original designs offer RF filtering to stop the hash emitted by the switch mode supply getting out. But economies on production find that leaving them out altogether (from just after the CE mark is approved), generates few complaints. That's because not so many users are trying to use radio alongside. The broadband hash generated can block receiver front ends at worst, but at least generate annoying noise that makes clear reception difficult.
There are some supplies that have good filtering in them, but there's no easy way to tell other than to try them out. (or if having a good knowledge of the circuit and examination of the componentry gives an indication)

 

[Leighb]

I have read this thread with interest as I had noticed that when trying to test my H/H VHF on the boat I was getting severe noise which no adjustment of squelch would suppress. I was thinking faulty radio, but I have a 12V USB charger plugged in by the chart table to charge iPhones. I am now thinking this may be the culprit. Will check next time I am on the boat.

 

[AntarcticPilot]

Examination of the circuit board of some of these devices (power supplies for notebooks, phones etc) reveals that many components are left off. The original designs offer RF filtering to stop the hash emitted by the switch mode supply getting out. But economies on production find that leaving them out altogether (from just after the CE mark is approved), generates few complaints. That's because not so many users are trying to use radio alongside. The broadband hash generated can block receiver front ends at worst, but at least generate annoying noise that makes clear reception difficult.
There are some supplies that have good filtering in them, but there's no easy way to tell other than to try them out. (or if having a good knowledge of the circuit and examination of the componentry gives an indication)

Not a new idea: see Muntzing (https://en.wikipedia.org/wiki/Muntzing). Apparently the guy would take a pair of wire-cutters to a circuit and snip away at bits he thought unnecessary until it stopped working!

 

[Alpha22]

I have read this thread with interest as I had noticed that when trying to test my H/H VHF on the boat I was getting severe noise which no adjustment of squelch would suppress. I was thinking faulty radio, but I have a 12V USB charger plugged in by the chart table to charge iPhones. I am now thinking this may be the culprit. Will check next time I am on the boat.

I was at sea for a day last year before I noticed I was not getting the shipping forecast announcements on Ch 16. Turned out it was an iPhone Cig-lighter - USB adaptor that was totally wiping out the front end of the VHF. Others I had on the boat were fine, but this one was terrible.
Beware, a lot of these very cheap electronics could be life threatening!!!

 

[Strolls]

In another thread previously, someone recommended, I think, the Omaker phone chargers:

http://www.amazon.co.uk/dp/B00NN43EYY

Although I'm not sure if the whole of this charger's body is aluminium, some of it is - this is supposed to act as a heatsink and prevent overheating.

Might the aluminium body also act as an RF shield, too?

 

[Leighb]

Update to my last post. I did some checking while on the boat today.
At first when I switched on the H/H VHF it was fine with no interference, squelch set to minimum.
I then pugged in alternately the 2 different iPhone chagers we have, and neither had any ill effect.

So what is the cause, after some thought I realised that the fridge was switched off, I turned that on and immediately severe interference, so that is the culprit. Question now is how to suppress the fridge?
I will post a separate question so as not to hijack.

 

[Dougal]

Update to my last post. I did some checking while on the boat today.
At first when I switched on the H/H VHF it was fine with no interference, squelch set to minimum.
I then pugged in alternately the 2 different iPhone chagers we have, and neither had any ill effect.

So what is the cause, after some thought I realised that the fridge was switched off, I turned that on and immediately severe interference, so that is the culprit. Question now is how to suppress the fridge?
I will post a separate question so as not to hijack.

Interesting. I assume the fridge is of the compressor type, and not an absorption fridge?

I still haven't got to the bottom of my VHF interference:-( I have got a number of (new) USB adapters, some permanently wired in, but they don't 'appear' to be the culprit. The only other new kit on board is a 120 watt solar panel and charge controller. I've tried setting the controller to 25, 50 and 100Htz, but nothing changes. Nor does the interference stop when I cover the panel. Still happens at night too. Maybe I need to actually DISCONNECT the controller from the batteries? Short of replacing my antenna and coax, I'm out of ideas:-(

The only coax test I know of, is a continuity test between inner and shield. Anything else i can do?

 

[Seven Spades]

Does anyone know what brand of USB charger VV Cox was using?

 

[vyv_cox]

Does anyone know what brand of USB charger VV Cox was using?

This one http://www.force4.co.uk/blue-sea-dual-usb-charger-socket.html?sqr=Usb charging&#.VqEZH6_fWrU

 

[Seven Spades]

Thanks, I have ordered one from a different manufacturer and the chap was very interested in this thread. He said I could take it on a sale or return basis. I am going to collect it tomorrow and fit it on Saturday.

What would you say is the easiest way to test it?

It will be interesting to see if all USB sockets are similarly affected or if it is a brand specific problem.

 

[Spyro]

I was at sea for a day last year before I noticed I was not getting the shipping forecast announcements on Ch 16. Turned out it was an iPhone Cig-lighter - USB adaptor that was totally wiping out the front end of the VHF. Others I had on the boat were fine, but this one was terrible.
Beware, a lot of these very cheap electronics could be life threatening!!!

Be wary of these cheapos. I have 2 of these. One came with a Sony phone and works fine the other came from ebay and works fine as a charger but causes terrible interference on my VHF and on the boat stereo. It does the same if I use it in the car.

 

[Seven Spades]

I wonder if it is the socket or the device that is causing the interference?

 

[Girona]

I too, have a fridge interference problem, that I am sure is specifically coming from the thermostat. It starts with a fast crackle, slowing almost to a stop, until the fridge switches on. Squelch will not take it out, I've tried a clean supply, direct from a battery to the VHF, I've checked the screening on the VHF cable. I would think a capacitor across the thermostat connections is the answer, but have no idea of what size, type etc to choose. Anyone help?

 

[Bru]

This one http://www.force4.co.uk/blue-sea-dual-usb-charger-socket.html?sqr=Usb charging&#.VqEZH6_fWrU

Did you actually get a Blue Seas socket?

Cos the last order I placed with Force 4 for that item, I didn't. What arrived was another make altogether. It was an urgent job and it seemed OK so I had to use it but words will be had!

(I use Force 4 a lot and don't normally have problems like this to be fair)

I've fitted a fair few of the genuine Blue Seas USB sockets with no issues so far

 

[William_H]

I too, have a fridge interference problem, that I am sure is specifically coming from the thermostat. It starts with a fast crackle, slowing almost to a stop, until the fridge switches on. Squelch will not take it out, I've tried a clean supply, direct from a battery to the VHF, I've checked the screening on the VHF cable. I would think a capacitor across the thermostat connections is the answer, but have no idea of what size, type etc to choose. Anyone help?

Try a capacitor of .1 microfarrad rated at 200v. Or even .01ufd olewill