This QRA Locator program was inspired by the PC EZ-QRA locator program by ON7VZ,
Daniel Vandewalle, as well as a much older MS-DOS program BD2000 by Michael Owen,
W9IP, and Paul Wade, W1GHZ/N1BVT.

When working from portable locations, it became something of a chore to have to
take a laptop with me simply to calculate my QRA. True, this is fairly easily
calculated by hand with a calculator and pencil and paper from GPS derived
Latitude/Longitude, but nevertheless what I really wanted was an implementation
that would run on my faithful HP-calculator, hence this program.

The file QRA.txt contains the source code with extensive explanations and comments,
the file QRA.hp is the calculator binary file. Simply transfer either version to
the calculator using the HP 48g, 49g 50g series calculator connectivity kit.

Note that if you use the QRA.txt file the calculator will strip off the comments
as well as re-formatting the source and losing all the pretty formatting.

For a complete explanation of the Maidenhead Locator System, please read the
accompanying PDF files, as well as the worked example.

The results from this program agree with those from EZ-QRA as well as BD2000. In
the latter program, for some reason the authors chose to invert the usual longitude
convention and consider east longitudes as negative, but otherwise the returned
QRAs, latitudes, longitudes, distances and bearings are the same.

After loading this program, you will see a folder QRA on your calculator. Press the
softkey to open this folder, and the left-hand softkey will be labelled 'Start'.
To the right you will see a number of cities, these variables contain the QRA text
strings which may be used in the program as example data. Otherwise simply press Start
to continue.

Although a certain amount of error checking is performed, the user is expected to
enter the latitude and longitude data in DD.MMSS format, north and east being positive,
south and west negative. Similarly, QRA text strings must be delimited with the " "
symbols and must be exactly 6 upper case characters and the digits 0-9 in the format
"AB12CD". The first pair of characters must be in the range A-R, whilst the last pair
must be in the range A-X. Failure to observe these constraints will simply result in
either an invalid result, or a RPL error message.

Since the code is in User-RPL, this should work on all HP-48/49/50 series machines.
The source file QRA48.txt contains the necessary modifications, whilst the file QRA48.hp
is the binary executable for the HP-48 series. It has been tested on both an HP-48GX and
a HP-48G, and worked correctly.

To locate the changes, use the file QRA.txt, and set your text editor to search for the
string: HP48

The file QRA.txt and its associated QRA.hp file are intended for the HP 49/50 series of
calculators. It has been tested on both a HP 40G+ and a HP 50G.

Adrian Ryan 5B4AIY / G3VJN / EI9KD
24 February 2011
