about nRF905

[Augustus]

I am currently working on a project using nRF905(a transceiver module). The thing confuses me is that I am not sure whether an antenna is necessary for the chip to function, or it is just an addition that can make the chip work better but not a necessity. Datasheet says ‘antenna can provide balanced RF output’, so I don't know for sure if it is strictly required.
Any help would be appreciated.

 

[(*steve*)]

I'm presuming this is the device you're talking about.

To me it looks like there is no on-board antenna at all.

There is no indication from the brief look at the datasheet that the unit will be damaged if operated without an antenna, but I would assume it would have very limited range without one.

edit: this paragraph means that you have to have *something*

The “ANT1 & ANT2” output pins provide a balanced RF output to the antenna. The
pins must have a DC path to VDD_PA, either via a RF choke or via the center point
in a dipole antenna.

 

[Augustus]

I'm presuming this is the device you're talking about.

To me it looks like there is no on-board antenna at all.

There is no indication from the brief look at the datasheet that the unit will be damaged if operated without an antenna, but I would assume it would have very limited range without one.

edit: this paragraph means that you have to have *something*

Thank you for your reply.
I think I will try it without an antenna and if it turns out ugly, I would add one.
Another problem is that on page 35 of the datasheet, it says C13 is not fitted. I don't know what that means. How should I choose the value of C13?

 

[NickS]

Thank you for your reply.
I think I will try it without an antenna and if it turns out ugly, I would add one.
Another problem is that on page 35 of the datasheet, it says C13 is not fitted. I don't know what that means. How should I choose the value of C13?

I don't think ugly is the right descriptor. It just flat out will not work. I can save you the time of trying and reinforce that your transceiver will neither transmit nor receive without an antenna. We don't use antennas just because they look cool.

Here is a low frequency analogy... I have an ipod connected to a 20W audio power amp and I am not sure if I will need speakers to hear the output. Perhaps I will just hook up the amp and see if it makes sound. Sure the amp will do its job of electrically amplifying the input signal but without the delivery mechanism(speakers) it may as well be a stapler because you will not hear anything.

Pages 32-34 of the datasheet give you some options for the antenna(either printed on board or connectorized 50ohm). If you are going through the effort of designing this chip into your project than do yourself a favor and don't neglect the critical link.

Best of luck
-Nick-