Try it handheld first. It won't be perfect but you'll hear the APRS and get a feel for how (not) precise it has to be. You're going to need the antenna either way. It's impossible for me to convey how extremely janky my first DIY antenna was for this. It's not a super-precise operation: https://www.youtube.com/watch?v=2y6A6ur7yas&t=520s