If you are like many recently licensed Amateur Radio operators your first purchase may well be a good Icom, Kenwood, Yaesu or other brand Handy-Talkie or HT two way radio. These are most frequently for the 2 meter and 70 centi-meter bands (144 and 440 MHz).
The antenna that comes with your radio is probably about 8 inches long and is a compromise between convenient length and performance.
After market antennas are available and just a quick turn away from installation to your radio’s BNC or SMA antenna jack. Some are very short and provide the worst performance. Some are quite long and provide some amount of gain.
Problems may arise if you use a long antenna on a radio that is mechanically design to handle the stock and antenna.
I have an Icom Z1A HT that is broken at the moment because I used one of those 18 inch or so antennas on it. The strain of that extra length loosened the antenna jack’s grip on the case and eventually caused the conductor between the antenna center pin and the HT circuit board to break.
I still have the radio in pieces, but cannot quite find an easy way to access the point where re-soldering is needed.
If I had it to do all over again, I would not put that long whip on a consumer grade radio like we have for our ham radio hobby. To be honest, I think the performance of the stock antenna was just as good or better on 2 meters.
The moral of the story is to think through the mechanical realities of putting an after market accessory on your expensive radio gear. If you do, you may well decide that what you have is good enough.