Could you tape a metal rod to a walkie talkies antenna to increase talking distance?

It can if you get it right but it may be illegal where you live.Distance impossible to know, depends on aerial type, weather, terrain etc.

For max range cheap aerial get a ball of rough hairy garden string and soak it in strong salt solution.

Fix a stable kite to it and fly the kite. Twist the lower end of the string round the antenna till tuning coupling is achieved.

Send message.

Code 3 Code 3.

Charlie Foxtrot Under attack area 14 Zone 6 Need escape route.. out

Code 4 Code 4

November Delta move north 2 miles. Bert's Lonesome Chicken Bar

Taxi ETA 1305 Zulu...out

Phew.......saved! Pesky mossies. Should have brought a spray can

as a communication engineer for 30 years i would say that would be of no benefit and more likely to detract from the proper operation of the radio, especially if it is a FRS unit. there is only one case where you would get a benefit, that is if this is a 2 meter Ham radio where the external factory antenna can be removed and replaced by an 20 inch rod. in that case performance of a 300 mw radio will become comparable to a 2 watt unit. it is unlikely to increase range as much as reduce battery consumption because of the low power setting.

No.

1: It would probably de-tune the radio.

2: It would violate the type approval, and regulations governing its use.