The following procedure will allow you to transmit on an extended
range (1.6-54 MHz for JST-245).
Remember, however, that on the 245 the internal antenna tuner works only in
the range 0-30 MHz.
I don't assume any responsibility about the following procedure,
neither for any consequent damage nor problem.
However, I have experimented the following procedure on my personal JST-245DXG
and I had no problems at all.
I found this "mod" as a photocopy among the pages of my JST-245
user manual. I don't know the source, but the procedure works good.
For the JST-145 the procedure is the same, even if it hasn't the 50 MHz band.