Changing the clock speed

I have an Arduino mega 2560, which has a default clock speed of 16MHz. I am using it with a serial baud rate of 9600.
I tried using the command:

void setup() {
CLKPR = 0x80;
CLKPR = 0x08;
Serial.begin(9600);
}

This works to reset the clock speed to 1MHz, however, it resulted in the serial output to be strange symbols at every baud rate option.

How else would I change this to 1 MHz? And how would this affect the serial baud rate/ input/ output?

Thanks!

larryg6464:
This works to reset the clock speed to 1MHz, however, it resulted in the serial output to be strange symbols at every baud rate option.

How else would I change this to 1 MHz? And how would this affect the serial baud rate/ input/ output?

Thanks!

But why do you want a clock speed that's soooo slow?

Power_Broker:
But why do you want a clock speed that’s soooo slow?

I just need the arduino to turn on an LED and leave it on while other tests are being run. The high clock speed constantly running gives off too much noise and interferes with my results. I’m trying to get the clock so low that once the LED is turned on, the effect of the arduino is negligible.

Do you know what code would help do this?

larryg6464:
I just need the arduino to turn on an LED and leave it on while other tests are being run. The high clock speed constantly running gives off too much noise and interferes with my results. I'm trying to get the clock so low that once the LED is turned on, the effect of the arduino is negligible.

Do you know what code would help do this?

No offense, but that sounds ridiculous. What other tests are so sensitive that the 16MHz clock signal causes EMI? How did you even identify that the EMI was from the clock signal?