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433 mhz RF antenna design

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wanchope

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Hi, all.
I am now doing a project on 433 mhz RF. What i am building is two seperate modules. One as a transmitter and the other as receiver. For transmitter i am using maxim's max1472 ask transmitter. Receiver side i am using a comparator circuit.
The projected communication range between these two modules is 1 to 1.5 meters. I already achieved it by using a quarter wave length whip (17.2cm) on both transmitter side and receiver side. But the ultimate product should be a handheld box with small antenna. It could be pcb antennas (loop, semiloop, modified dipole) or microstrip antenna. However when i tested other forms of antennas, the communication range drops to about 0.3-0.6 meters.
Did any one have any ideas of building tiny antenna for 433 mhz applications? Any ideas is favorable.

Wanchope
 
They do sell antennas etched on PC boards for this purpose - they are said to perform quite well. You might try Newark Electronics, Digikey or a place like that to see what they have - just for ideas.
 
Actually i did. I tried Linx's microstrip antenna, but seems not so satisfactory. And i also make my antenna using some copper fold. Also not that good. The best is the modified dipole, but the size is quite big.
I think this is quite a common problem in antenna design for handheld device. Did anyone else have some thought? Thanks.
 
wanchope said:
Actually i did. I tried Linx's microstrip antenna, but seems not so satisfactory. And i also make my antenna using some copper fold. Also not that good. The best is the modified dipole, but the size is quite big.
I think this is quite a common problem in antenna design for handheld device. Did anyone else have some thought? Thanks.

There's nothing 'magic' about aerial design, basically the bigger the better! (assuming correct design of course).

The reference for all aerial system is the dipole, and gains are normally given as referenced to that.

Anything smaller than a dipole is going to have a poorer performance than a dipole. A quarterwave whip is basically a dipole, the other half being 'reflected' in the ground plane.
 
Linx Splatch

The SPLATCH antenna from LINX works very well for this type of application. If possible send all of your digital grounds directly back to the source via slightly larger traces, Your analog grounds should go directly to the ground plane. The SPLATCH is optimized for a ground plane that is 1.5" by 3". Using this size or having a similiar surface area will dramatically effect your range. Also, be sure that there is not a ground plane under the SPLATCH antenna. Lastly, make sure you have some filter capacitors in close proximity to your transmitter and receiver power pins (0.1u in parallel with 22u should work).
 
Don't forget that orientation becomes more important
as you move away from isotropic. Make sure that your
polarization is correct (i.e., that elements of the receive
antenna are in alignment; both vertical or horizontal or
at least at the same angle), and that you are in the
pattern on both ends. A quarter-wave or half-wave
will probably be the most forgiving of misalignment,
so anything else becomes more sensitive.
Also, be aware that other designs may, and probably
will, have a different feed impedance, requiring some
sort of matching circuit to the transmitter and receiver.

<als>
 
I have an electric garage door opener. The transmitter is about the same size as a keyfob, yet the range is about 30meters down the road.

You are talking of a range of 1 to 1.5 meters. If you cannot get that range with an etched PCB antenna then perhaps you have a problem with the modules?

.
 
I purchased a 433 mHz antenna from Mouser, it was only 5 cm long and has only one terminal. I connected it directly to the transmitter output and was able to receive at 1000 feet using a parabolic reflector. It is cheap, $2.75, part number 240-4311-121-20043 (www.mouser.com).
 
when you design 433mhz rf module antenna, when it is a external one like whip, then the best antenna height will be 17.28 cm / 6.80 inch, and you can use short whip or helical antenna to have a shorter designed antenna.
 
You might post your receiver circuit. It might benifit from some gain.
 
Very old thread.
 
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