RF Signal Generator or RF & AF

I am new to A.M. radio repair. I would like to buy a signal generator. I have noticed that some generators are RF (only) and other generators (like an old Heathkit T-3) have RF & AF functions. Is the AF function necessary for the later stages in the radio? How does one know if a generator is a "sweep" generator (other than the fact that is says "sweep" in the model #)? Any recommendations on a good signal generator to look for on the Bay for under $100? Thanks to all! Steve

Usually the reference to "audio," is that the RF signal generator can be modulated by a tone of some frequency. Usually the lesser expensive generators use a 1,000 KHZ audio tone. This will allow you to modulate the RF signal and then follow the detected tone through the detected audio section. I've found old, cheap, signal generators do all I need to do, trouble shooting, IF alignment, etc. A frequency counter is a good think to have also.

Sweep generators are used in television.
They are used for checking thevertical, and, horizontal sweep circuits when having problems.
Billl Cahill

I have one of the sencore am fm signal generators and love it. I have had good luck with it and the time it was broke it was easy to fix. It has a setting for the stages such as the 455 khz IIRC and its easy to use. I can inject a audio signal an a rf as well with it. I can input on the antenna and then a signal in the audio area as well. I see them pop up from time to time. I have a few sencore items and they have been great with the exception of the scope I have. I think the scope was just worn out or a dud. I am thinking of replacing the scope.