I live in a residential area and I want to test and design an antenna in my garage. I plan on using my signal generator as the power supply and a RTL - RDS dongle connected to my computer as the receiver. The signal generator spans from 0 to 60 MHz. The amplitude has a range of 5 to 20 volts. My question is will my em waves interfere with my neighbors? If so what can I do to test designs and not affect the neighborhood?
Consider buying an antenna analyzer. This is exactly their use case.
An antenna analyzer is a device that injects a low power signal into an antenna and measures complex impedance. This is done over a range of frequencies.
As an example, mine cost a few hundred US dollars and works up to 500MHz. There are many brands at different price points, each using different methods for accomplishing the task so it is worth reading reviews to understand what makes them special. Mine was a little more expensive, partially because of the extended frequency range and partially because it is capable of determining the sign of the complex frequency.
Regarding voltage level, asked in an above comment, that really depends on the antenna's radiation resistance. The parameter of interest is radiated power (v^2/R). I do not know what the FCC limit is, but it is likely below 0.05 watts, possibly far below. If R is 50 ohms (reasonable for a quarter wave dipole, but very low for a folded dipole) then max V is under 1 volt.
Aside from the being technically illegal to be radiating like that (unless you're below the CFR47 Part 15 unintentional radiators limit, at 5V highly unlikely unless your antenna is really inefficient at those frequencies):
Off the top of my head, most people would notice AM radio, CB some of the (really) old RC control stuff. You'll be hitting several Amateur Radio bands- they may find you before the FCC van does (if you're in the USA) as well as a bunch of international radio bands, amongst other (government) services for long-range communications and radiolocation services. FCC maintains a table for usage even if not detailed, you have to go to the CFR sections to pull those details out.
Priority 1 is to reduce your signal strength output- absolutely no reason to be transmitting high field strengths it's all linear.