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Antenna design for 434 MHz RF reciever module

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a bazooka dipole is a bit different. a bazooka dipole uses a pair of tuned sections of transmission line to create a broadband dipole. this is a simple dipole, but the feedline is concentric with one of the elements, so you don't need to have the feedline entering the feedpoint perpendicularly.
 

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But I don't think he's in Europe. He's in the USA. Therefore, you're saying he'll have to modify his frequency to 315MHz.
He can either move to 315 or get a ham license. :p

(Just for reference, although 434MHz is in the middle of the 70cm ham band, its use is authorized in section 15.240 "to identify the contents of commercial shipping containers" in "commercial and industrial areas such as ports, rail terminals and warehouses." They might be using a fair amount of power. Of course this isn't the OP's application, but possibly another reason the OP might want to move to 315.)
 
he should get a module that's in one of the ISM bands....... or one of the "whitespace" bands.....
 
try this simple antenna made from coax cable (and you can use RG-174 cable which is the same diameter as 16Ga wire). make the dimension for each of the two elements (the exposed center wire and the folded-back braid) equal to 19cm. you can skip the part about copper tubing, and just fold back 19cm of the ground braid over the cable insulation. keep the braid intact so it acts like a metal sleeve over the outside of the cable. this will give you a good half-wave dipole (each element, the folded back braid and the center wire are each 1/4 wave) that doesn't need to be supported because it's the end of the cable. at the other end of the cable, the center wire connects to the transmitter antenna terminal, and the shield braid connects to the transmitter ground (either a metal shield or a ground trace on the pc board will do)

Hi Unclejed613,

I built an RF remote control using 434mhz TX & RX modules(ASK) which is giving me a poor range i.e., less than 12 feet with 12V at TX. As of now, I am just using 17 CM vertical wire as antenna on both TX and RX. If I use your design will it improve the range? Can you please describe clearly how much should be the total length of the antenna for 434 mhz and how much length should be covered by shield wire and how much inner wire should be expose? Do I need to use any capacitor between the antenna feeder point and ground? Thanks in advance!
 
try this simple antenna made from coax cable (and you can use RG-174 cable which is the same diameter as 16Ga wire). make the dimension for each of the two elements (the exposed center wire and the folded-back braid) equal to 19cm. you can skip the part about copper tubing, and just fold back 19cm of the ground braid over the cable insulation. keep the braid intact so it acts like a metal sleeve over the outside of the cable. this will give you a good half-wave dipole (each element, the folded back braid and the center wire are each 1/4 wave) that doesn't need to be supported because it's the end of the cable. at the other end of the cable, the center wire connects to the transmitter antenna terminal, and the shield braid connects to the transmitter ground (either a metal shield or a ground trace on the pc board will do)

While this type of design is pretty efficient there are a few other things to consider.
He is flying the balloon to say upto 100m and at this low altitude is likely to be underneath the balloon. If this antenna is dangling vertical underneath then you will have a problem. You are likely to be under the main horizontally polarised lobe and therefore getting a very reduced signal from the antenna.
He would be far better using a circular polarised patch with lobes extending down to the ground.

I will post a drawing when I can get Visio to behave.
 
I can see this is a fairly old post but with regards needing a license to operate at 434Mhz. No you do not need a license or have to sit any exams! There are plenty of low power radio modules available for data transmission just like in your balloon project, so just go ahead and enjoy yourself if you haven't already!

I'm currently building my own point to point half duplex link and will shortly be experimenting with dipoles or yagi. No license is required.
 
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