If I took One of my Lower-Power 2.4 GHZ xBees and built a MOSFET (or other powerful semiconductor) based amplifier and boosted it to say… 5000mw 
, what would happen? would that work? I’m talking legality aside, I’m aware the FCC would be knocking on my door at some point…
But is it possible? Would an OP-AMP have a place in this system? How would you do it? seen any Tutorials around about this? Any advice or technical experience would be nice.
No, it would not work for a number of reasons.
1- An XBee is both a receiver and a transmitter so you need a way to switch from TX to RX (think of a walky-talky and when you press the button to talk).
2- The frequency is 2.4 GHz (2,400,000,000 Hz) and needs a device that will operate (have gain) at that frequency.
3- Due to the frequency the PCB layout is very, very critical and not easy to design.
In theory if you wanted to do something like this look for IC’s Amplifiers that are designed to work at 2.4Ghz. The PCB layout is still critical and you’ll need a tx/rx switch but the makers of these parts usually have design guides and App Notes with examples.
What if I used a 900 MHz xbee?
This design is for 433mhz radios (SparkFun sells the same model)
http://www.flytron.com/pdf/7w_booster_schematic.pdf
That design is fairly simple and do able, does lower frequency require less critical pcb layout? If I bought this would I be able to boost 700mhz radios? Do I need a switch, Or are the radios only one way? Could 2 radios be set at similar frequency and operate without a switch. :? I’ll stop the parade of questions and give u time to catch your breath.
Thx from tim
The drawing in your link does not show much but it looks to be an RF amplifier module on a PCB. Note all the additional components and the layout.
Lower frequencies are easier but 900MHz and even 433MHz still requires a proper PCB layout and component selection. Not for beginners in electronics.
The simple 433MHz SparkFun units are a transmitter and a receiver which is a ‘one way’ transmission and therefore an RF amp on the TX output would work (however, this would NOT be Legal as this is in the Ham Radio 70cm Band which is protected by the FCC).
Any of the XBee type RF modules are Transceivers and are ‘two way’. They typical send data to another module which then sends an ACK back to the sender. These would require a TX/RX switch.
Adding an Amplifier sounds like a good way to increase the range but this is not really a good idea since it will cause interference to other radios. A much better way to increase range is to use a directional antenna. This way the increased RF power is in a smaller area and not omni-directional. This is less likely to cause interference (note: interference of a licensed radio service is illegal and the FCC will do do something).
If you really like RF and radios I suggest you look into obtaining a Ham Radio license. This allows you to build and experiment with all sorts of radios ‘on the air’. I have a license and this allows me to use many of these circuits legally.
Even if you don’t go for a Ham radio license get a copy the the Ham Radio Handbook from the ARRL. It has lots of info about radio circuits and how they work.
Do you already use the XBee PROs? they are 50mW or so, rather than 2mW in the non-PRO.tim.vrakas:
If I took One of my Lower-Power 2.4 GHZ xBees and built a MOSFET (or other powerful semiconductor) based amplifier and boosted it to say… 5000mwBut is it possible? Would an OP-AMP have a place in this system? How would you do it? seen any Tutorials around about this? Any advice or technical experience would be nice.
Does one end or both have an XBee with a U.fl antenna connector, and you have a gain antenna?
With the Pro, and the immobile end of the link being a 6dBi omni antenna, the other end being a PRO with a PC board antenna, I’ve obtained a half mile range with good error rates.
Not practical or necessary to build amplifiers. You can use antenna gain. In addition to the above, you can use a directional yagi antenna to get the gain up to about 14dBi. There are 12dBi omni antennas availalbe- about 5 ft. long. (Don’t buy the marketing crud about gain with 10 inch antennas.
Also… be sure to use XBee Pro Series 1. THe XBee Series 2 are ZigBee only and struggles with the ZigBee protocols will appear to be RF signal conditions problems. Series 1 can be run in simple peer to peer, one to many, without ZigBee and even without need for a PAN Coordinator.