A Question for the sciencey lot amongst us

[Banshee]

Alex get out :lol ........ I joke, I joke :nenau

So, I use a Belkin FM Transmitter in my Terrano because in an aim to keep the truck as OEM as possible, I've opted to keep the original Nissan Headunit. This then allows me to play anything I want providing it has a 3.5mm audio jack on it on an FM frequency of my choice, tune in on the radio and, voila, I have my own radio station :kissy

So here's the question, what is it that I hear coming over the speakers when I accelerate, it sounds like my engine on helium, but I can only hazard a guess at it either being noise from the alternator or gearbox?

 

[solarman216]

got to be alternator, why gearbox? there is nothing on it bar switches for reverse light and 4 wheel drive but there is a little gizmo on the speedo that sends speed data to the ECU, Rick

 

[Banshee]

got to be alternator, why gearbox? there is nothing on it bar switches for reverse light and 4 wheel drive but there is a little gizmo on the speedo that sends speed data to the ECU, Rick

OK Rick, so what causes the Alternator to cause the speakers to cause that noise though?

 

[solarman216]

OK car alternators are three phase ac devices that via the diodes come down to dc battery voltage all this produces noise on the whole system, so on the output close to the alternator you need to put a capacitor which smooths the output,, cannot tell you the microfarad value off hand but will be readily available from any motor factors, Rick

 

[Lazy-Ferret]

As Rick says, most likely the alternator, as the suppressors do wear out over time. The other less likely places are the speedo as that is electronic on some (well mine) or maybe the Tacho.

The problem is with the later 2, trying to suppress them is much harder as they need the voltage spikes to work.

The first job is to work out where the noise is getting in.

First see if it is the head unit, does it do it on other inputs. Often you need to have the volume a lot higher than normal on those units like the Belkin, so the noise may be always there, but the volume of the music from the other inputs masks it better.

Next try moving the Belkin and the device plugged into it, to different locations in the car, does it affect the noise.

Also the cable that goes between the Belkin and device, is that built in, or do you supply that to suit the device, in which case try a shorter lead, or one with better screening.

Sent from my GT-I8160 using Tapatalk 2

 

[bry]

Also you should be able to get a suppressor for the lead. (Clips on).

 

[supergnome]

Have you tried ferrite rings on the leads? Not sure how many coils but woth a try.

 

[Lazy-Ferret]

Have you tried ferrite rings on the leads? Not sure how many coils but woth a try.

Did someone say FERRET RINGS??

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[firebobby]

Did someone say FERRET RINGS??

Sent from my GT-I8160 using Tapatalk 2

:lol Trust you :lol

 

[Sweety]

Engine whine is common on the FM transmitters:doh as said a suppressor will prob be needed but i'm sure your truck has a normal single din stereo so simply changing the stereo for something better would be far easier sound wise & suppressors don't always work

 

[Blocky10]

I use one of these. Cheap as chips and works great, assuming your cassette player works ok.

 

[jims-terrano]

Another connection method is. Does the head unit have a socket to support a multichanger? If so do a google for a company called "connects2", they male simple devices that plug in to the multichanger sockets and gives you a 3.5mm input without the need for the radio transmitter. Cost me about £20 for one for my Renault but seen them for other models too.
As for the noise probably alternator but could be say the cps sensor creating a pulse that changes frequency with engine speed.

 

[Barrbeast]

I use one of these. Cheap as chips and works great, assuming your cassette player works ok.

That's what I use too :thumbs

 

[rustic]

If you have a seperate 12 volt battery, totally isolated from the car, then fit a cigar socket to that, then the FM transmitter, then observe any improvements.

You can also try other FM frequencies.
Try moving the Belkin to other locations around the dash too..

The electrical noise might be wire borne, and not transmitted, so some supression is required.

Capacitors are used as close as possible to the source of the interference, but a choke or inductor ( ferites have also been suggested, but they tend to be used for very high frequencies ) in the supply line to the Belkin can reduce the whining. You might also need a choke in the ground supply too.

Hope it helps,
Rustic

 

[Thomas-the-Terrano2]

is belkin powered by cigar lighter?

my fm unit is powered by own micro usb charged battery and not had noises.

is noise from power wire, thinking nack in day cb radios suffered from ignition
noise on petrol cars. a supressor was needed.

 

[Banshee]

Some nice ideas floating about there, cheers for the info guys

is belkin powered by cigar lighter?

my fm unit is powered by own micro usb charged battery and not had noises.

is noise from power wire, thinking nack in day cb radios suffered from ignition
noise on petrol cars. a supressor was needed.

The transmitter is powered by a 12v cigarette socket and usually sits on the passengers seat, I transmit on 89.9 as that is the clearest frequency round by me