I have an arduino that controls a quadcopter that receives radio comunication using 433 MHZ. I know I must use a 1/4 wavelenght to get optimal results. But I would like to put my 17 cm not entirely vertically in the top of my arduino, and not entirely vertically on the bottom of it (point below). I would like to keep half of my antenna pointing above my quad and the other half pointing bellow my quad. Can I get this 17 cm and connect the middle of it to my transmitter?
Usually people connect one end of the wire to the transmittr and the other end is left alone. Can I leave the 2 ends alone and connect my RF module (sold its antenna hole) to the middle of my antenna?
You just want 17cm sticking up, the rest of the circuit and quadcopter
wiring acts as a ground plane.
If you had nothing else in the way you could have a centre-fed dipole which would be
34cm long, but you'll also need a 50 ohm coax feeder to its centre and insulating rod to
support it....
[ A 1/4 wave aerial over a flat ground plane is exactly equivalent to a dipole BTW ]
I suspect the best would be downwards, in practice there might not be space.
Have the antenna at 90 degrees to the basic metalwork/structure/wiring and
avoid detuning it. In particular the end of the wire needs to be well away from any conductor.
Do you want range, or not?! In your other thread you've beat us to death trying to find some way to get slightly better performance, now you want to make it smaller at the expense of range.
Put the radials in the arms of your quadcopter and point the antenna straight up or straight down. Don't coil it. It is typical to put it into a light plastic tube to keep it straight. Stranded wire is often used just because it can take the continued vibrations and flexing without breaking.
gilperon:
17cm is not easy to put in the quadcopter, harder is keep it in vertical. I will use a plastic tube to keep the antenna straight
Perhaps easier to make the antenna from flexible (stranded) wire and attach a small weight to the end. It can then collapse on landing but will hang straight down in flight.
As others have said, plastic coating will have no measurable effect on the range.
gilperon:
Just got me wondering: instead of keep the antenna straight down (using some weight to keep it straight down [very good idea, I admit!]) can I make a "bow" or a "rainbow" with it? I mean, using the rainbow shape with my 17 cm wire? Instead of keep the wire straight down, can I keep the wire in the upper surface and bend it fo make a rainbow shape? Will it keep its performance?
How often have we specified keeping it straight - or near enough?
Were you not answered in #17 that making a pendulum out of it would be a very bad idea?