Antenna question

[zachtheterrible]

This is the artwork for a 900MHZ transmitter using a pre-built RF module. The pins lined up horizontally is where the circuit plugs in. The last pin on the right is the antenna pin. The antenna is a whip antenna. I have quick question:

Did I do it correctly? The datasheet said that there should be a groundplane horizontal to the vertical antenna, which is a piece of wire in this case.

 

[Nigel Goodwin]

This is the artwork for a 900MHZ transmitter using a pre-built RF module. The pins lined up horizontally is where the circuit plugs in. The last pin on the right is the antenna pin. The antenna is a whip antenna. I have quick question:

Did I do it correctly? The datasheet said that there should be a groundplane horizontal to the vertical antenna, which is a piece of wire in this case.

Perhaps you might have made the picture somewhat smaller?.

The groundplane refers to a solid sheet of copper on the upper surface of the board, connected through to the ground points on the bottom - so you require a double sided board. However, you don't need to etch the top surface, you can simple countersink the holes where the components pass through.

 

[zachtheterrible]

Sorry about the picture, I realized how large it was after i posted it :lol:

The large portion of copper on the bottom of my board is ground. Wouldn't this count as a groundplane to my antenna?

 

[Russlk]

Your groound plane should be at least 1/4 wavelength. But, Yageo makes a ceramic antenna that does not need a ground plane. Mouser sells it for $7.65. If it works as good as the 433 mHz antenna that I bought, it will be as good or better than a 1/4 wave whip (but I think it is directional).

 

[zachtheterrible]

I don't have room for 1/4 wavelength, that would be 3 inches @ 900 MHZ.

Oh yes, another question: I am using a 1/2 wavelength antenna. I assume there's nothing wrong with that.

 

[Russlk]

The transmitter is no doubt designed to drive 75 ohms, the 1/2 wave antenna, when end driven, is high impedance. You will not have any radiated power. The Yageo antenna will be much smaller than 3 inches, the 433 mHz antenna was no more than 2 1/2 inches long.

 

[zachtheterrible]

Thanks russ, I cut both the transmiter and receiver antennas to 3 inches and have about twice the range! :lol:

 

[Roff]

Sorry about the picture, I realized how large it was after i posted it :lol:

Zach, don't you use the preview button? It's particularly useful when you're adding an attachment.

 

[zachtheterrible]

Ron, I believe I've never used the preview button before, I'll have to start :lol: