HAM Radio 1/HamRadio.cdr/packet/thenet08/r95.doc

Text File | 1991-12-29 | 3.6 KB | 75 lines

RADIX 95
--------

Is a binary to text conversion program written by Greg Jones, WD5IVD and
Dhanapong Saengrussamee for packet radio.  Transfer of 8-bit data on packet
can be accomplished with appropriate parameter settings on the TNC.  However
problems arise when sending 8-bit data through the current Bulletin Board
store and forward network.  The reason for this is because the BBS codes use
certain 8-bit characters for control purposes.  Binary data can fail due to
some 8-bit data characters being interpreted by the BBS code as a BBS control
function.

A need arises then for a way to convert binary data to a 7-bit format which
can be transmitted through the BBS network, and then be converted back to
the original 8-bit data.  Existing conversion schemes can accomplish this,
but they all increase the original file size.  For instance the HEX encoding
process can increase the original file size by as much as 100 percent.
Character Prefixing conversion methods typically increase the original file
overhead by 84 percent.  The RADIX 64 conversion method reduces the overhead
amount to typically 33 percent.

With RADIX 95, overhead is further reduced, varying between 17 and 24 percent,
depending upon file content.  Other 8-bit to 7-bit conversion schemes may
reduce the overhead even further, but suffer from increased processing time
in accomplishing the conversion.

A convenient procedure to process binary files is to first use one of the
compression programs, such as PKZIP on the binary format.  PKZIP typically
reduces the file size by 40 percent.  The ZIPPED file is then converted to
the RADIX 95 format.  Using this procedure, the processed file size is then
nominally 25 percent smaller than the orignal.

One feature of the RADIX 95 utility is it allows a file to be "Split" into
smaller segments.  These segments can be transmitted over a period of time
and can be "Combined" by application of the RADIX 95 program at the receiving
end following receipt of all segments.  Large files can then be reduced
into a series of sizes capable of being accepted by the transmission medium.
Over a number of VHF nodes or on HF, 2K segments can usually be accomodated
without serious network disruption.

Upon recombination of the R95ed segments, the user "Decodes" the RADIX 95
file and then PKUNZIPS, to restore the file to original format.

RADIX 95 format
---------------

The top line of a RADIX 95 file will read:

(RADIX 95 - [filename:date])
Filename is the first 8 characters of file name.
Date is - MM/DD/YY.

Each line of RADIX 95 produced will be 70 characters long.  No other
information should appear after the 70th character.

The file ends with:
 (RADIX 95 - END FILENAME)
Where filename is the first 8 characters of the file name.

RADIX 95 will search a file's first 10 lines (one that is to be converted
back to 8-bit data) for "(RADIX 95" before attempting a file conversion.
If "(RADIX 95" is not found within the first 10 lines, then the program will
provide an error response and abort.

Overall commands and operational information are available within the
RADIX 95 program at "F1".  For more information see the article on RADIX 95
in the ARRL 7th Computer Networking Conference manual, page 107.

An added benefit of RADIX 95 is in the way binary control functions are
encoded, users along the circuit with their TNC MONITOR function "ON" will
not experience disruptions to their screen!  Screen disruptions are agrevat-
ingly common when monitoring the transmissions of standard binary content.

73 de Jack, [e-mail]