Question: For a normal 5 watt handy working in VHF or UHF freq with 50 ohm antenna , is it possible to use a same length coax cable instead of a stub antenna, so as to work like a crude antenna. Will this only result in extra capacitance/ VSWR damaging the system ?

Answer: 
If you want an antenna at the end of a length of coax, in my experience, simply stripping the last 1/4 wave of coax and leaving the inner exposed, does not work. The VSWR is high and unstable, as the other half of the dipole is completely undefined.

What works a lot better is to carefully extract the inner from the braid, or re-attach the braid, and fold it back down against the coax. So now you have a 1/2 wave dipole, with the coax running down against the lower, grounded half. You could even put some heat shrink over it, but it's better to keep the braid slightly away from the coax.

If you have access to a VSWR meter, try building these and running your hand down the coax. In the first case the VSWR changes dramatically as your hand moves, in the second it will be more stable.

If you want an antenna directly on the HT without any coax, then stripping off the sheath is fine, and a quick and easy way to get a 1/4 wave monopole without soldering. Your tuning will almost certainly be wrong on your first try - either cut it while attached to an MFJ style antenna tester, or try a range of lengths and see which ones work best for getting in to distant repeaters.
youtube has a video of a piece of coax with the last 19" being separated between the center, pulling it out of the sheath. poor mans dipole. seemed to work
<http://bit.ly/2scIYD7>