High the cheapest starting option is
HF Radio JOVE project which is the simplest and cheapest of all of them.
As a matter of fact I was going to sell my JOVE stuff to make way for
Molecular Hydrogen Hydrogen detection which is a bit more complicated.
I still need to place my stuff in a metal box.
The above are the 2 most common projects, they get a bit more complicated and expensive after the above two.