Here is my home-built, cloth iron soldered, range extender for CC1101 (included onboard) RF transceiver chip from Texas Instruments. You could say that it is a CC1101+CC2591, but for 868/920MHz band. I used MAX2233 RF amplifier from Maxim-IC. It can deliver up to +24dBm (250mW) of RF amplification with +10dBm of input.
You can download the project files at the bottom of this page by clicking on red "download" button.
A few basics of CC1101 chip:
After adding RF amplifier, original power of 10mW is boosted to almost 250mW or 1/4W. MAX2233 RF amp can deliver up to 250mW when powered by 3.6V, and since I used 3.3V LDO on my board, the output RF power is little less than that.
Even though all electronics on this modem work on 3.3V, everything is still compatible with 5V TTL levels which is done with a help of MAX3377 or MAX3378. The power is lowered from 5V to 3.3V by MAX8888 LDO and it can provide enough mA to supply CC1101, MAX3377/8 and the PA.
For testing I used two modems and two antennas (it figures). At the transmitting side I used monopole antenna for GSM - 900MHz, and for the receiving side I used directional yagi also for GSM - 900MHz. Details of these antennas can be found here: monopole and yagi.
In this quick test I easily achieved over 1000 meters (or 3300 feet) of range and the test-location/terrain configuration can be seen on the map: Transmitter location, and receiver location. This was achieved even without the antenna on the receiver's side! Then it started to rain and I had to go back. Oh and, I used 1.2 kbps data transfer for maximum receiver sensitivity. The data package transfered was 1 byte address and 4 bytes of payload long.
For testing I used ATmega16 and the source-code can be found in the RAR archive for download.
All capacitors = eBay shop
Soldering of components
You would probably think that this board is impossible to solder at home. Well, I will just say that I didn't even touch my board with soldering iron or hot-air reflow iron. It was all soldered by using a solder paste and a home cloth iron. It seems that cloth iron can get hot enough (200 degrees of Celsius) to perfectly solder everything down! It sure was exhausting to place a solder-paste on every pad with a syringe needle. Instead of cloth iron you can use a hot-plate, so check this out and see how it's done.
Exported from cc1101.brd at 02.04.2009 15:55:31