AM RF antenna question

hi all, im using AM 433mhz transmitters and recivers in something im working on. I found a formula to calculate wire size for aerials and came up with the length of 17.5cm.

at the moment ive got them soldered straight into the circuit boards ive etched for testing, but to extend the range I would like to have them mounted outside the house.

in doing this it would mean that the aerials would be about 2-3 metres away from the pcb's, so the length of them would be way over whats recommended.

whats the best thing to do in this situation? I really want to get the maximum possible range from them

You use a coax cable from the pcb to the antenna. Connect the coax shield to the pcb's ground plane. That will allow the coax to act as a transmission line and not an antenna.

Read this thread about dipole antennas. This dealt with 100Mhz, but the feedline discussion applies to 433Mhz, too.

of course yes that makes perfect sense.

does it make any difference having a coiled antenna over a straight one?