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The "Holy Grail" of wireless flash triggers are the Pocket Wizards - they are fast, reliable, and have an amazing range. This of course comes a quite a heafty price and many new photographers simply can't afford them. For this reason many people use the Cactus V2's from Gadget Infinity, otherwise known as the "Ebay" triggers.

There are many features that the PW have that the V2's don't have, but as far as cheap wireless triggers go, the V2's are quite good. The main problem of the V2's is in their range, but with a small modification this can be remedied fairly easily. Basically, by adding an external antenna the signal is "louder and clearer" for the receivers to pick up.

The original article where I found this modification can be found here:GI Cactus V2s Modification Tutorial

Here is my experience with this mod:

1. Tools
   The first thing you need is some tools. Here is a list of what I used and recommend you have before getting started:
   1. Soldering Iron and Solder
      You can get these from Radio Shack. I used a 25W iron and Rosin Core Solder for PC work.
   2. Helping Hands
      These are not required, but if you don't have someone helping you these are very useful, especially when you are trying to solder the wire to the connector and the board.
   3. Drill and Drill Bits
      Cutting the holes without these would be very difficult. I used a 5/64 bit for the starter hole and a 1/4 bit for the final hole.
      
   4. Screw driver
      I used a small philips head to remove the small screw on the bottom of the transmitter.
   5. Wire Cutter
      Pretty obvious here. Also a wire stripper is nice to have to strip the ends of the wire, but not necessary.
   6. Pliers and 5/16 Wrench
      I used these to tighten the antenna connector to the top cover.
2. Trigger/Receiver Combo
   I bought the wireless trigger/reciever kit from Gadget Infinity. I use Canon equipment, so I bought these: Wireless Flash Trigger V2s for Canon 580EX II 420EX
   I'm pretty sure they are all the same, but they have different titles to make it easier for people to find what they need. You can double check they will work with your equipment by looking at the list of compatible items in the description. Make sure they are the V2's and not the older models. ( I think the older models simply had "PT-04" on the front.)
3. Antenna & Connector
   I bought the antenna and connector. You can buy both of these from Digi-Key (part numbers below), but you don't have to. Many people used antennas from other devices such as old cell phones, while others used simply a wire. I really like how clean it looks with the bought antenna. Also buying the antenna I knew it was for the 433Mhz wave length. Note: There are calculators out there for figuring the length of wire for a specific wavelength.
   Digi-Key Part Numbers: Antenna: ANT-433-CW-RH Connector: CONREVSMA004
   
4. Opening the Transmitter
   I started by taking the transmitter apart and taking the battery out. To open the transmitter remove the screw on the bottom and lift the cover from the front.
   
5. Drill Starter Hole
   After opening the transmitter I needed to drill the hole for the antenna connector. I found the best way to figure out where to make the whole is to use the washer as a guide. I placed the guide up against the screw hole and the plastic piece next to it as shown below. (I've built two of these, and both had "the plastic piece") I drilled a small hole in the center of the washer to get started and insure the larger hole is in the proper place. If you don't have the plastic piece, use the close up image below to figure out where you need to place the washer.
   

   (Close up of the starter hole. I used a 5/64th drill bit here.)

   

6. Drill Actual Hole
   Next I drilled the actual hole. I used a drill bit that fit inside the washer. I used a 1/4th drill bit for this, which was slightly smaller than the washer, but it worked perfectly.
   
   
7. Inserting the Connector
   I attached the connector and used pliers and a 5/16th wrench to tighten it. I put the washer on the bottom because I liked the clean look on the outside.
   
   
8. Soldering the Wire
   I soldered the wire to the two parts. I chose a wire of about 6 inches. In the first one I moded, I used a slightly shorter wire and my tests between the two show that the longer wire works better. I also chose to put the wire on the right hole on the board, next to the TR2 label. Some poeple soldered the wire to the small hole near the 616 label. I think that if you use the TR2 hole then the length of the wire should be the full 1/4 wavelength of 433Mhz (6.82 inches), but if you use the 616 hole then you need to subtract the length from the TR2 hole to the 616 hole. I use a length in between and seems to work very well.
   
9. Reassemble
   The last part was to put the battery back in, close the enclosure, and screw on the antenna.
   
10. Conclusion & Test Shots
    The overall performance of the transmitter improved dramatically. Without the mod I was getting about 25 feet reliably with intermittent fires at 30 feet. After the mod I was getting much more...see images below.

    Click on the Thumbnail
    
    
    Maximum distance with Test Button Only
    (When I took the images from this distance the flash did not show up on the image. At 1/200th of a second I think the flash fired too late.)

    
    Maximum distance with max sync speed 1/200th sec
    (This is as far as I could go while retaining the flash in the shot.)