How do you do that? Find that distance apart at which you can communicate -- but with difficulty. Shorten the antennas slightly -- test for improvement -- if you see improvement shorten some more.
If it gets worse -- you need longer antennas -- start over. Sorry about that -- try 18cm -- then shorten as per above instructions.
No this is not quite right.
The antenna needs to resonate. The 17cm length is approximately 1/4 of the wave length of the frequency in use. The antenna should be cut for the frequency being used. If a 1/4 wave whip is not sufficient, then you can add a ground plane. The ground plane would be a few wires at right angles to the whip and 20% longer. Someone mentioned a dipole. That's two legs, each 1/4 wave long, one fed from the center fo the feed line and the other connected to the braid. These are directional, with signal radiated off their sides.
If this is not adequate, you can build more complex directional antennas.
One could say that anything is not quite right.
Amirra is an engineering student. She rarely asks a second question in any area. She can read and figure things out for herself. Never ever give an engineering student too much information -- they take great pride in their ability to figure out things that don't yet know.
I pointed her to places that would fill in all the details I left out and that everyone else left out.
So... Those radios are never quite on the the freq. you expect. One would think if shortening the antenna does not work -- lengthening might work. However un-cutting the wire is not that easy -- starting over again with a piece "too long" seemed simpler to me.
I do think I got it right -- but I did get a chuckle.
You made my day.