I would back away from all the "function generator" type devices.
They are OK for EEs & the like to use to produce complex waves & to play with digital stuff,but you need a real signal generator for radio work.
This pretty much means three things:
(1) Old & big & fairly cheap
(2) Modern & worth as much as a small car
(3)Atten or similar Spectrum Analysers with a Tracking Generator.
They are reasonably cheap.I've used a similar SA,but can't vouch for the Tracking Generators.
As you, like most Electronics enthusiasts,are probably quite poor,it probably ends up being (1).
Brands for (1):
HP,Marconi,Boonton,Philips,maybe Heathkit--all stuff you might find at a Hamfest!