This will show you how to add a RF power amplifier to your Proxim Symphony for under $50. The cost is reduced by using the existing components on the Symphony, such as the PIN diode switch, and just inserting a higher power final amplifier.
Adaptation to wireless network cards other than the Symphony should be trivial.
Most schematics are in their native Xcircuit PostScript format for ease of printing and modification. To use PostScript under Window$, you'll need to install the Ghostscript & Ghostview packages. Set Media to A2 for ease of viewing.
- 2.4 GHz 1 Watt Power Amplifier Schematic
Start by reading the data sheet for the RF Micro Devices RF2126, you'll find out quickly that it's a tiny little 8-pin PSOP 2.4 GHz amplifier IC. If you are up to working with this device, call RFMD up at 336-664-1233 and order a few (around $7 each), or ask if they will send you some free engineering samples.
You'll want to pick up some quality 1/32 inch, double-sided, one ounce copper clad FR-4 circuit board. The Injectorall circuit board from Digi-Key is perfect. Its part number is PC44-ND for 3 x 4.5 inches and costs $3.23. You should also pick up the Toner Transfer System design paper by DynaArt, part number TTS-5-ND for a 5-sheet pack. This will allow you to print the circuit board pattern, out on a laser printer and then iron it onto the copper clad board. This is probably the best, and cheapest, way to create your own printed circuit boards.
The next step is to make the circuit board for the amplifier. You should use the board pattern RF Micro Devices provides! This is because the delicate 50 ohm strip lines that are needed are a real pain to recreate on your own. Here are some links to help with the fabrication of your own printed circuit board:
You will need to modify the supplied circuit board pattern to allow for the two voltage divider resistors. Just cut into the trace leading to pin 3 of the RF2126 with a razor blade.
After your circuit board is etched, you should drill and solder all the ground vias. Those are what connects the top copper plane to the bottom plane on two sided copper clad boards. Do this by drilling a small hole where the marks are in the circuit pattern picture (the white dots in the above JPEG), then solder a piece of wire in the holes to connect the top and bottom planes. Cut off any excess length of wire flush to the copper plane. You can then start to solder in all the discrete components. Start with the small surface mount capacitors and inductors, then move to the larger components. The very last thing to solder in will be the RF2126 IC. This is done to protect the IC from any extended handling. You should then install PC board mount SMA jacks to quickly allow you to connect the amplifier up. Note that this is all easier said than done :)
If you are a wuss, RF Micro Devices sells completed evaluation boards for the RF2126 for around $150 each. All the parts are already installed and it even includes SMA jacks.
Pre-made PC boards are now available for this project through FAR Circuits.
You'll need to unsolder the large RF shield to get access to the insertion points.
Where to insert the new amplifier module
So now that you have about one watt RF power output into a high gain directional antenna, does this mean you can establish a wireless link fifty qazillion kilometers? Nope. Microwaves are line-of-sight, no matter what the power is. The higher power will overcome smaller obstructions, like trees and leaves, but it still won't cut through that hill in the middle of your link path.
So why bother?
Chicks dig RF burns.
Technically, the fact that frequency hopping systems don't spread their signal results in no processing gain. Processing gain comes from the increase in power density when the received signal is despread. This helps to improve the received signal's signal-to-noise ratio. In other words, frequency hopping systems will need to put out more power in order to have the same signal-to-noise radio as a direct sequence system.
View some of the construction pictures.
+5 & +12 VDC Tap Points
Open solder pads for +5 & +12 VDC
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