So, to expand slightly on this....
In the USA most radios require FCC Type Certification to be sold. This is basically the manufacturer and an "independent" test lab filing test results and promising that the radio meets the FCC rules for the particular radio service it's intended for. This is an attempt by the FCC to make sure the radios sold in the USA meet the technical requirements.
Your Motorola TalkAbout radio has type certification under two distinct sections of Part 95. Part 95 is for the "personal radio services".
The two parts for your radio are FRS and GMRS. They are two distinctly different radio services, even though some of the channels are shared.
Under the FCC rules for FRS:
§95.194 (FRS Rule 4) FRS units.
(b) You must not make, or have made, any internal modification to an FRS unit. Any internal modification cancels the FCC certification and voids your authority to operate the unit in the FRS.
(c) You may not attach any antenna, power amplifier, or other apparatus to an FRS unit that has not been FCC certified as part of that FRS unit. There are no exceptions to this rule and attaching any such apparatus to a FRS unit cancels the FCC certification and voids everyone's authority to operate the unit in the FRS.
Since your radio will work on FRS channels, this rule prevents the manufacturer from making the antenna removable. FRS was always designed to be a short range radio service, so the 500 milliwatts limitation on the FRS channels is an attempt to keep coverage fairly short and allow the limited number of FRS channels to be reused in close proximity.
Removing, modifying or replacing the stock antenna would violate the rule, void the type certification and, if you want to follow the letter of the law, make it illegal to use the radio in the USA.
Yeah, I know, no one is going to catch you, no one out there would be able to tell the difference unless they were actually looking at your radio, but I'm just passing on what the letter of the law says. Please don't shoot the messenger.
So, since your radio covers the FRS channels, this is the limitation, according to the FCC.
It's kind of a shame, since there isn't anything in the FCC rules limiting the Effective Radiated Power of FRS, only the transmitter power (500 milliwatts). Manufacturers could build FRS radios with more efficient antennas, however the end user/consumers really like compact, cool looking radios, and long antennas don't meet this. Many years ago Icom sold and FRS only radio, there were two sub-models, one with a short stubby antenna and one with a longer more efficient antenna. Not sure how the longer antenna models sold, but it was sort of rare to see them anywhere but "special order".
Now, here's what you CAN do:
1. Get your GMRS license. It's $70 bucks or so, last time I checked, for 5 years. You should technically have one for the radios you have if you are using the GMRS channels, but again, no one really checks.
2. Ditch the consumer grade radios and get something designed for the job. There is no shortage of suitable radios out there.
The nice thing about getting away from FRS is that the FRS limitations go away. Once you are -just- GMRS, you can have removable antennas, run up to 50 watts, repeaters, etc. With a good radio and a well placed repeater, coverage of 50 miles are more is possible. Many years ago I had access to a GMRS repeater on a mountain range near me. I used to talk in excess of 100 miles with either my mobile radio or a portable radio, through the repeater.
But, back to your original question:
The antennas are not removable on purpose. There isn't a secret antenna jack hiding inside your radio. You could crack open the radio and wire up an external antenna jack, but it would require some light fabrication and some soldering to do correctly. Then you would be able to add whatever you wanted. But, as I mentioned above, the legality issues come into play. You'd need to decide how comfortable you were doing this.
The big limitations on these radios is lack of efficient antenna. You are on the right track. The other limitations is usually receivers that are lacking in the sensitivity department. Usually these consumer grade radios are not adjusted very well as the roll down the assembly line.
