is the 5 watts of power not enouph to either talk over the drive thru person or do i have to talk when the actual person is not talking
Short answer, it depends.
There are many factors at play. Probably the most important is how close the drive thru person is standing to the repeater. If they're right underneath it, that drastically reduces your chances of getting overtop of them with only 5 watts. If they're a few dozen feet away, you stand a much better chance. Your distance away from the repeater is equally as important. Obstructions between you and the repeater, likewise obstructions between the drive thru person and the repeater are also factors. Antenna gain is something they can't change on their end but you can on your end. If you can manage to muster up an extra 10dB in antenna gain, that'd be the same as increasing your power from 5 watts to 50 watts.
Check out the Field Strength Calculator at
http://www.daycounter.com/Calculators/Maximum-Field-Strength-Calculator.phtmlCourtesy of the FCC, the drive thru person is probably transmitting 120mW (FCC ID search grantee code BYM). You're transmitting 5000mW. Due to the FM capture effect, the stronger signal at the repeater receiver (strongest field strength at the receiving antenna) is the signal which will get through/repeated. Here's some examples:
If the drive thru person is 3 meters away from the repeater, at 5W you need to be 19.36 meters away or closer to have a stronger field strength. In reality, this figure is probably going to be smaller assuming that you have the body of a vehicle and a brick wall or two between you and the receiver where the drive thru person does not.
If the drive thru person is 10 meters away from the repater, at 5W you only need to be within 64.55 meters of the repeater. As you can see, it's proportional. The further the drive thru person is away, the further you can be away and still be successful.
What effect does extra power have? Let's use our 3m example again. Your 5W is good at <19.36m. You bump up the power to 50W and you can be as far as 61.24m. Extra power not an option? Use a better antenna. An antenna with 10dB more gain is the same thing as increasing the power by a factor of 10. 3dB gain is the same as doubling your output power.
HTH
