Hello,

I have a RF module (cc1120) which is transmitting on a frequency of 434Mhz. The signal received in another RF module, 1 km far away. The problem is that the dbm of the received signal is sometimes too low (-108dbm). I am wondering what can I do to extend the signal range & strength. Note that the mcu on the board is a low power mcu and saving the battery is very important for me.
I would be glad to hear different idies in order to solve this problem.

Thanks

 

If the transmitter and receiver are in fixed locations then you could use directional aerials to direct more of the available power in the required direction.
Put the aerials outside so the building materials do not get in the way.
Make sure you have 'line of sight' between the aerials so the signals can travel unhindered between them - for instance by raising them higher.
These measures will make best use of the available power.

 

If the transmitter and receiver are in fixed locations then you could use directional aerials to direct more of the available power in the required direction.
Put the aerials outside so the building materials do not get in the way.
Make sure you have 'line of sight' between the aerials so the signals can travel unhindered between them - for instance by raising them higher.
These measures will make best use of the available power.

By "aerial", do you mean something like :
https://goo.gl/images/13uSWT
? Can you guide me which type of aerial to buy ?
What about putting a repeater in the middle of the distance ?

 

You can google 433MHz directional aerials. For instance, I found this one: http://fpvlab.com/forums/showthread.php?10584-Beer-CanTenna-A-ground-antenna-for-433MHz-TX

 

You can google 433MHz directional aerials. For instance, I found this one: http://fpvlab.com/forums/showthread.php?10584-Beer-CanTenna-A-ground-antenna-for-433MHz-TX

I need for a 434Mhz. Will a 433Mhz direcrional aerial also suit ?

 

Yes. It would be a very special aerial which had such a low bandwidth that this would be a problem.

 

Yes. It would be a very special aerial which had such a low bandwidth that this would be a problem.

What would be a problem ? The low bandwidth ? Can you please reccomend me on such aerial ?

 

What would be a problem ? The low bandwidth ? Can you please reccomend me on such aerial ?

To be clearer, any aerial intended for 433MHz will work perfectly well at 434MHz.
I do not feel qualified to recommend an aerial. I do not have experience of comparing aerials.

 

Here are a few home made 70 cm antennas:
http://users.belgacom.net/hamradio/schemas/yagi_uhf_antenna.htm

Beneath each design is a diagram of the projected directional signal strength.

 

The problem with buying antennas is that the data given is not real and that their testing is done poorly so the data given is bad. Most antennas are usually made for a wide range of frequencies unless is a very specialized expensive antenna from a reputable company, so I suggest you to make your own or tune modify one cheap one and test its gain, freq. and return loss with a network analyzer in the far field but then you are getting into a very complex subject that will take years to master.
Networks Analyzers and calibration kits used to be extremely expensive and most professional ones still are but there are companies that make decent ones for lower freq. at a cheap price like the DG8SAQ from SDR kits.

 

http://uk.farnell.com/lprs/yagi-434a/antenna-yagi-7-element-434mhz/dp/2096215