Originally Posted by nakman
And yes, you could technically blast any frequency through any antenna with some reduced capacity
The relationship of 145MHz to 445MHz is such that they do not share a 1/4λ multiple fundamental. If you key on 70cm into a 2m antenna it's probably going to see a high reflection.
There are ways to make this work, a gamma match or making the antenna into a sleeved dipole, etc. But typically mobile monopole whips use a trap to make a long antenna electrically correct for 70cm, say a 1/4λ 2m into a 3/4λ 70cm or 1/2λ 2m into a co-linear 70cm.
All solid state radios made now necessarily (tube radios tolerate high SWR much, much better) shut down on high SWR, which is why you could probably key up and not ruin your radio. It might even leak a little RF onto the antenna, but it won't be much (like milliwatts).
If you do it long enough with high enough power, you'll fry the protection shunt. It's all about heat, any power not doing work exciting electrons (which requires antenna resonance or apparent resonance with caps and inductors helping) is converted to heat, which is the sworn enemy of transistors.