The question is..

Will 75Ω resistor be fine for my experiment?

My radio's specifications are 3.0V, 0.14 A (based on my multimeter's reading) I guess it was 148 milliamps.

I used the formula given by SgtWookie. And found out that the resistor I need is 77.428571428 . I chose 75Ω because it is the closest among 68 and 82Ω.

Anyway, I am not about of wasting the power. I just want to see if it will work or not.

P.S. My power source will be 13.8 V .

Formula

Rlimit = Vsupply - (LED*numbers in series) / Ampere

13.8V 3.0V * 1 0.14

13.8V 3.0V 0.14

10.8V/0.14A

=77.428571428 OR 75Ω

Final question: Will radio work with 13.8 V battery with 75 ohms connected?

thanks and pls. answer if it will work.

any help will be appreciated.