Removing/filtering/ignoring noise in a signal line

I am looking for ways to remove noise from a signal. As well as pinpointing the noise.

I have this oscilloscope here from EICO (model 460) that has a cameo performance as a signal tracker for a phone line in the 1970's Batman tv series, which means in the 70's this thing must've been old, as it was used for a prop already. although the one I have actually has more knobs and controls than batman could afford.

Anyhow, how can my oscilloscope help me get rid of or find my noise issues? I really haven't done much with oscilloscopes in school except to help visualize some IO lines and PWM control.

I have the large FP sign I'm sure some of you have seen, there are 16 distinctly different length ground lines, and it turns out, most of these are varying from 8ft to 13ft, which happens to be in the entire range of FM radio. Without testing help from you guys, I cannot say if this was my issue, or if I simply have a power supply issue changing my logic levels. How can I test this?

What is an FP sign?
I doubt it is FM radio unless you are really close. Maybe tou can post the circuit that is giving you trouble?

"FP Sign" refers to the actual LED display sign, because it is an F and a P, standing for "Fantastic Planet"

I'm not sure what kind of EMI it is, but this sign definately drops everyone's cell phone calls whenever they get near it when it is not turned on.

So you are the transmitter, not the receiver. It could be your leds are driven with pwm????? If so the long wires and high switch rate may be the problem. Move the led driver closer to the leds.
To see it (If your scope has enough bandwidth) you could just put it on a low scale and use a small loop of wire from the scope probe to scope probe ground and "sniff" around. I may have the whole vision wrong. Maybe a picture or two??