Batboard

At work we regularly use battery operated golf carts with our ht1000 pac-sets and we get an incredible amount of feed back. Is any one else experiencing the same thing and how did you fix it? We are using the AAR freqs. And the feed back only happens on two thirds of the carts. Thank you for any help.

Precisely what kind of "feedback" are you getting? Do you mean you're getting audio feedback or that you're getting EMI on the recieved (or transmitted) signal?

Probably what he is referring to is the noise from the pulse-width-modulated motor controllers on the carts. They chop the DC from the batteries at some frequency (usually in the kHz to MHz range) to control the motor speed. If the radios in question are directly connected to the batteries they will, in all likelihood, get an ENORMOUS amount of noise from that.f

If that is the case, the first thing to do is to try using the radios without any electrical connection to the cart (e.g. from a completely separate battery). If the noise is still present, then it is being transmitted by the cart - there will be little you can do about it save putting ferrite cores on every wire in the cart and hoping for the best.

If it DOES NOT happen with an isolated radio, the put the best RF noise filters on the power leads to the radios that you can find, and see if that will reduce the problem to manageable levels.

Thanks for the replies. First, it is not an isolated radio.We use motorola ht 1000 and kenwood handheld radios and it happens to them all . Second, are the ferrite cores expensive or should I just give up and live with it. BTW when we push the "gas" pedal down that is when we get the noise thru the radio. Thanks again for your input, artman.

artman wrote:Thanks for the replies. First, it is not an isolated radio.We use motorola ht 1000 and kenwood handheld radios and it happens to them all . Second, are the ferrite cores expensive or should I just give up and live with it. BTW when we push the "gas" pedal down that is when we get the noise thru the radio. Thanks again for your input, artman.

Have you contacted the manufacture of the carts? They may have the info you need, and if you push them they may supply you with the parts to fix it. If they don't want to help, just tell them you will buy another manufactures products next time. I know most of the RR's around here use gas powered 4 wheelers in the yard.


Jim

I wonder if the noise is coming from the speed controller or the brushes on the motor. I dont know if the switching frequency of the controller is high enough to create spurs at 160 MHz, but if the motor brushes are sparking, that would make lots of wideband noise.

I know on smaller motors, they use a network of two or three low value capacitors from the terminals to the case, and that blocks a lot of RF noise. I'm not sure if that would work on motors this large, though.

If you have access to a Spectrum Analyzer dial up the freq(s) and put the golf cart by the anaylzer. It will tell you if its RF generation from the cart or internal noise on the dc circuit. You can start from there for a solution.

Fowler