Saturday, March 24, 2007

Updating PC-HFDL for New System Tables

We've had some confusion over how to copy the new pchfdl.dat file into PC-HFDL's configuration folder to update its frequency list (ARINC System Table #31 / 0x001F hex).

The file linked from this blog is identical to the one available on the PC-HFDL Yahoo! group. That's where I got it. I thank this group for making it available.

Not everyone can access the files sections of Yahoo! groups, since a Yahoo! login is needed, while a mailing list can simply be read in e-mail. Therefore I have been posting copies of these files to the Utility World web site.

Here is the procedure for installing pchfdl.dat as the new frequency file for this excellent program. This is how I have done it for several system table changes now, and it has worked every time:

How to update the PC-HFDL System Table with pchfdl.dat:


This file updates the internal system table used by Charles Brain's commercial version of PC-HFDL, a program for the Wintel PC which decodes ARINC's High Frequency Data Link signals.

The HFDL system stores its frequencies in a common list called the System Table, which is changed every few months as HF propagation conditions change with the seasons. The system table number, which is transmitted by the ground stations, is incremented by one.

Ground stations transmit the new list until everyone has it, and no aircraft has a table number mismatch. This usually takes only a few days. PC-HFDL cleverly grabs these transmissions to update itself, and stores them in a file called pchfdl.dat. When PC-HFDL detects a new version of the System Table, it automatically updates this file.

An issue exists where, if PC-HFDL is not running or there is no clear reception at the right times, it will not receive the transmissions needed to update this file. This causes the display of frequencies in the squitter screen to change back to numbers rather than kilohertz, making the program much harder to use. Therefore, the user is told how to update this file manually.


1. Get a copy of a pchfdl.dat file that someone else has made with the program since the new frequencies were transmitted. There is usually one on the Yahoo! HFDL group within a few days, which I change on my site at the same time. This file should be treated as a binary, whether or not it is. If it is read on the screen, it will look more or less like total nonsense, but the program knows what to do with it. Download the file to your disk by right-clicking on the link, then choosing "save target as," "save link as," etc. Make sure it downloads to the desktop or some other place where you can find it quickly.

2. IMPORTANT! Close PC-HFDL before going any farther!!! You won't break anything if you don't, but the frequencies won't update.

3. Find the directory that PC-HFDL runs from. This is usually C:\Program Files\PC-HFDL. Change to this as the active directory.

4. In this directory, there should be a subfolder named configs. Change to this as the active directory.

5. In configs, find a file named pchfdl.dat. It should be around 24K. Rename this file something like oldpchfdl.dat, or pchfdlnn.dat, where nn is the number of the former system table.

6. Copy the pchfdl.dat you have just downloaded to this subfolder. It should now contain your old data file, your new pchfdl.dat, and three other files. It's safe to open these others, but don't change them! One of these, systable.txt, is a human-readable version of the System Table that is written out once pchfdl.dat is processed. Another, pchfdl.txt, lists the ground stations. The third, pchfdl.ini, is the binary initialization file that stores the previously used configuration of the program.

7. Go back to the desktop or start menu, and run PC-HFDL. Find a nice loud ground station with the squitters and click the box. The numbers should once again be replaced by frequencies.

Good listening!