FanCausing TV Signal Interference

[GorillaToast]

I had a 12v fan connected to my Accessories breaker, and when it was on it would cause digital interference and loss of signal. I have the tv and an amplified antenna connected to the same circuit. Last night I move the fan to a different circuit, but it still causes the interference.

Anyone have a fix?

Btw, I already have a small o2 Cool fan for not so hot nights.

 

[Don S/V ILLusion]

There is a fix by adding toroids to the leads but the cost and effort will likely exceed the cost of a new fan which will meet radiation standards and not cause this in the first place. If you are set on trying to mitigate the noise generated from the fan, a search of RF interference and toriod coils should give you plenty of help. Keep in mind the fan motor will still create noise and the toroids will only decrease it, not eliminate it completely.

 

[Bill Roosa]

Is your antenna amplifier grounded to the boat ground or through the DC negative wire?
The amp is just doing what it was designed to do.
Try unplugging it from the TV with the fan running and see if the interference decreases.

 

[GorillaToast]

Is your antenna amplifier grounded to the boat ground or through the DC negative wire?
The amp is just doing what it was designed to do.
Try unplugging it from the TV with the fan running and see if the interference decreases.

It is grounded thru the DC negative wire. If I unplug the amp, I lose the signals for most OTA stations.

 

[GorillaToast]

There is a fix by adding toroids to the leads but the cost and effort will likely exceed the cost of a new fan which will meet radiation standards and not cause this in the first place. If you are set on trying to mitigate the noise generated from the fan, a search of RF interference and toriod coils should give you plenty of help. Keep in mind the fan motor will still create noise and the toroids will only decrease it, not eliminate it completely.

Don, it's a cheap truck stop fan. No coils. Do you know offhand if the expensive boat fans at WM will not cause this RF interference?

 

[Ross]

You could turn off the TV.

 

[Don12364]

In the days when car ignition used a contact breaker it was common for this to spark and cause interference on the radio. The cure was a 'suppressor' connected across the contacts. i.e. a capacitor. I suspect you have a fan with a brush motor and it is sparking just like the car contact breaker.
If auto shops still sell such items I suggest connecting it across the fan.
I have one I fitted to my panel that I put there to eliminate a similar source of hash.

 

[Don S/V ILLusion]

Don, it's a cheap truck stop fan. No coils. Do you know offhand if the expensive boat fans at WM will not cause this RF interference?

It depends on the bandpass of the amplifier you have. Some amps are too broad and will amplify everything; others just amplify a limited freq range so I can't answer your question about a different fan without knowing the specs of the amp. Rather than make this as complicated as possible, what I'd do is just go buy another fan anywhere and return it if the problem persists at which point you can try adding toroids on both power leads.

 

[Mark Maulden]

Take the fan power and gnd and twist it (maybe ~18 turns/ft) and connect directly to battery and see if it works. Radiated emissions are mainly from wiring. I would also use separate routing for the fan separated from TV amp (and other) by several ft if possible. If not, try for maximum separation as even inches can make a difference. Ships batteries are the best capacitors, however, any sources have to be direct to batteries. Other wiring (ie panel wiring in series) introduces series inductance which can render batteries/filters useless.

 

[weinie]

try a ferrite bead on the wire from radio shack.

http://www.radioshack.com/product/index.jsp?productId=2103222

 

[philwsailz]

GT-

In the powerboat world where we often see multiple audio amplifiers, noise from fans, as well as trim solenoids, ballast valves, etc. is a common problem. A non-polar electrolytic capacitor wired in parallel with the offending load, (in your case the fan) will take care of the noise issues. I typically recommend a 50V 100 uF non-polar cap. wire from your +12v wire to your ground wire, RIGHT AT THE FAN.

In the audio world these will be known as crossover capacitors. In the CAR AUDIO world you will find these sold at your local car sterel shop as BASS BLOCKERS.


I have implemented this solution for countles DIY stereo guys on other audio forums to eliminate pops and whines from their amplified audio systems. While I have not implemented it on a TV installation, I have a hunch the capacitor might just do the trick for ya.

It is a cheap fix, so slide by your local car audio retailler and ask about a set of bass blockers. They are sold in pairs, so you will get more than you need, but we are talking 3-4 bucks tops. Otherwise, go to Parts Express or MCM or a local electronics shop and see if you can get a non-polar cap of the value listed above.

A quick Google Shopping search provided the following quick exaqmple of what we are looking to use. http://david-levy-company-inc.amazo...src=froogle&utm_medium=CSE&utm_source=froogle

Good luck and post up whatever solution you find that works!

 

[zeehag]

i dont have a tv but my fan interferes with wifi signals--lol--i just turn off the fan......

 

[kenn]

A non-polar electrolytic capacitor wired in parallel with the offending load, (in your case the fan) will take care of the noise issues. I typically recommend a 50V 100 uF non-polar cap. wire from your +12v wire to your ground wire, RIGHT AT THE FAN.

This is my first suggestion too... except that since the capacitor is going across a 12v DC line, there's no need for a non-polarized cap, and GT can simply use a cheaper 'polarized' cap, such as a 100uf/25v electrolytic cap - just observe the polarity marks and besure to connect the + lead to +12v, the negative lead to the other. If in doubt, check the voltage at the fan and mark the + lead.

(Electrolytic capacitors hooked up backwards tend to, um, explode. More startling than dangerous, but then you have to vacuum up lots of little paper bits. Don't ask...)

These are available at just about any electronics parts store.

More elaborate measures, such as adding a series inductor, are possible, but the cost of more elaborate protection might exceed the price of a better, less-noisy fan.

 

[Steve Dion]

Have you considered getting another fan and see if you have the same issue?

 

[philwsailz]

This is my first suggestion too... except that since the capacitor is going across a 12v DC line, there's no need for a non-polarized cap, and GT can simply use a cheaper 'polarized' cap, such as a 100uf/25v electrolytic cap - just observe the polarity marks and besure to connect the + lead to +12v, the negative lead to the other. If in doubt, check the voltage at the fan and mark the + lead.

(Electrolytic capacitors hooked up backwards tend to, um, explode. More startling than dangerous, but then you have to vacuum up lots of little paper bits. Don't ask...)

These are available at just about any electronics parts store.

More elaborate measures, such as adding a series inductor, are possible, but the cost of more elaborate protection might exceed the price of a better, less-noisy fan.

I usually will recommend a non-polar due to the fact that the noise often emulates an AC signal, modulated on a DC line.

FYI

 

[Don12364]

FWIW: My Raymarine Autopilot was biting great chunks out of my +12v supply every time the motor started up. This interfered with VHF radio and everything else. Who says the boat's battery would take care of this?
My only solution was to connect a 2,200 µF 24v computer grade capacitor directly across the radio supply at the main panel.
This, in addition to the car contact breaker suppressor - which is only a 0.1 µF capacitor suitable for hi frequencies anyway - cleared up all the sources of interference.

 

[Don S/V ILLusion]

FWIW: My Raymarine Autopilot was biting great chunks out of my +12v supply every time the motor started up.

That should not occur. You might want to beef up the size power cables to eliminate that v drop.

 

[Don12364]

No Don, I would need to increase the resistance in my autopilot supply cables to reduce this effect! Of course this would be counterproductive for the pilot.
The VHF radio is as near straight across the house battery as I can get. i.e. on the panel connected directly to the house master switch. The battery cables are as Hunter installed probably about 0AWG.
What I believe was happening was that the startup current for the Raymarine's very small motor was affecting my VHF but only when I was transmitting. All my friends complained of the loud click every few seconds which, of course, I couldn't hear as I had the pressel switch down.
The 2000 μF just quenched this click a treat.
I concluded that the batteries are not a really low impedance at low radio frequencies.

 

[Forrest15112]

No Don, I would need to increase the resistance in my autopilot supply cables to reduce this effect! Of course this would be counterproductive for the pilot.
The VHF radio is as near straight across the house battery as I can get. i.e. on the panel connected directly to the house master switch. The battery cables are as Hunter installed probably about 0AWG.
What I believe was happening was that the startup current for the Raymarine's very small motor was affecting my VHF but only when I was transmitting. All my friends complained of the loud click every few seconds which, of course, I couldn't hear as I had the pressel switch down.
The 2000 ?F just quenched this click a treat.
I concluded that the batteries are not a really low impedance at low radio frequencies.

Sounds to me like your batteries are unable to supply the full load you put on them. They could be old and weakening, or just too small. I don't understand how more resistance would improve it.

The capacitor would have been better suited near the autopilot motor instead of the radio, but hey, if it works...

 

[zeehag]

the boatyard interferes with my wifi reception--when they haul or splash a boat, wifi interrupted....oh well.....