Greetings All:
The following is presented as an alternative and supplement to the use of a
BPSK schema for having a QSO across the North Atlantic. The following
proposal is presented as a way to make maximum use of existing skills with
Visual CW and very slow bit rates that have been successful in getting
amateur signals across the North Atlantic on a regular basis. The BPSK
schema being proposed is more elegant and make vastly better use of the
available propagation time in any one day.
This email proposes a 7 level FSK coding schema for use over the North
Atlantic. The schema requires a DDS level of frequency control device that
can be driven from a computer serial port and is stepable in discrete steps
permitting FSK levels in the order of 30 to 50 milliHz. A demonstration of
this capability will be presented by va3lk in the coming weeks.
The schema is based on a center frequency, called "space" which is 1/2 unit
long and is the main carrier frequency of the transmission. In steps
increasing in frequency, step size to be determined to fit the observing
program being used, the first step represents 1 "dit", the second step
represents 2 "dits", the third step represents 3 "dits". In steps of
decreasing brequency, step size to be determined to fit the observing
program being used, the first step represents 1 "dash", the second step
represents 2 "dashes", and the third step represents 3 "dashes".
really so very simple isn't it.
_ < three dits
_ < two dits
_ < one dit
- <center frequency
_ <one dash
_ <two dashes
_ <three dashes
Thus my call appears as follows
_ _
_
_ _ _
- - - - -
_ _ _ _ _
_
V A 3 L K
The less prevelant characters have the most coding but that is ok they do
not happen that often.
The transmitter runs continuously during the transmission period since there
are no unkeyed spaces between characters.
My goal was to find a schema that permits a full QSO to occur in under two
hours of time using a technology that capitalizes on the experience gained
with Visual CW with bit times of 60 seconds. The results of a QSO completed
using this process will I am very sure meet the demands of our community for
the elements of a valid contact having occured upon completion of the
process. I did not say the demands of all members of our community, just a
very significant number of our peers will agree that a contact has occured.
The members of this group will be those who have a vested interest in the
success of the attempt.
I have prepared simple programming routines in Basic to allow any PC to send
this type of FSK when the PC is connected via an RS-232 line to either a
G4JNT DDS board or a Qualcomm Q2334 DDS evaluation board.
The visualization above may be difficult for some, this is reasonable with
all the different fonts etc, I will provide a .JPG file of an actual
transmission as soon as possible. Comments and what ever to myself please.
Larry
VA3LK
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