[HTC EVO 3D] Whosdaman:
Before I go into the full details of the project, let's go over what a PRL is, what it does, and why it matters to you.

What Really is a PRL?

"The Preferred Roaming List (PRL) is a database residing in a wireless (primarily CDMA) device, such as a cellphone, that contains information used during the system selection and acquisition process. In the case of R-UIM-based CDMA devices, the PRL resides on the R-UIM. The PRL indicates which bands, sub bands and service provider identifiers will be scanned and in what priority order. Without a PRL, the device may not be able to roam, i.e. obtain service outside of the home area. There may be cases where missing or corrupt PRL's can lead to a customer not having service at all.

On many networks, regularly updating the PRL is advised if the subscriber uses the device outside the home area frequently, particularly if they do so in multiple different areas. This allows the phone to choose the best roaming carriers, particularly "roaming partners" with whom the home carrier has a cost-saving roaming agreement, rather than using non-affiliated carriers. PRL files can also be used to identify home networks along with roaming partners, thus making the PRL an actual list that determines the total coverage of the subscriber, both home and roaming coverage."

Source: Wikipedia

TLDR

: The PRL tells a device what towers to connect to, which frequency to search on, and in what order to connect to them. This includes "on" and "off" network towers. PRLs do not effect 4G WiMax performance.

Why Should I Care?

The PRL directly effects the coverage you receive and the data speed performance of your device. Ensuring you have the latest PRL is critical to maintaining the best signal your device will get. However, there are a few "special" PRLs we can use in order to gain access to hidden features, such as 3G data roaming.

So What is This About?

I'm glad you asked. I've been working on this for a few months now and I'm now ready to go public in order to gain more statistical data from my fellow peers. I have a collection of PRLs that I have rigorously tested to see which ones give me the best performance. This isn't enough. I need real world testing for as many members as I can get.

While I can't give the full details of my project away yet, let me assure you it will benefit everyone on Sprint. Phase 1 of my project has already started and here is how you can contribute:

https://docs.google.com/spreadsheet/ccc?key=0ArqBGjrbNosddGR3OURoNnJLdTlTaEo1RmVEYjdVNlE

The above document is open to everyone and can be edited by everyone. This spreadsheet will be used to compile data from everyone's usage of the PRLs available to us. Check the bottom of the file for sheet of each individual PRL. Each one has it's own sheet. Just add your data for which ever PRL you are testing.

The tool accepted for measuring data speed is Speedtest.net. They are the industries leader in speed testing, and it is a very reliable application.

If the PRL you are testing isn't there, I have included a template sheet so you can make your own sheet. Please stick to the format and be honest. This project is for everyone to benefit from, so don't ruin it for anyone. Also be sure you are adding your raw data to the correct PRL sheet. Little mistake like that can skew the data. Please test "Home" and "Roam" equally, I am trying to obtain the best performing PRL overall. I want to repeat that 4G WiMax is not effected by PRL, so do not include 4G in your testing.

Be impartial, be true, be consistent, and most of all be precise. If you notice something is wrong, fix it. You can chat inside the document. Just check the top right hand side for the people viewing the document. I will check this document often and update it regularly.

I have included the primary PRLs for testing in the 2nd post, and instructions how to manually update your PRL from a PC in the 3rd post. If you have any questions, please feel free to ask away.

[UPDATE: 3/4/12]

- Closed private testing

- Added ##3432# to 3rd post

[UPDATE: 3/6/12]

- Revised 3rd Post

- Added Nexus S 4G support

- Added Disclaimer to 2nd Post about Network Vision PRLs

[UPDATE: 4/2/12]

- Phase 1 of private testing is through. Haven't posted results yet

- Added new updated version of PRLs in 2nd post

- Updated guides in 3rd post