I find your work and your informative descriptions of what you're doing always very interesting.
Thanks John. Steve. On 02/13/2012 03:56 PM, John Douyere wrote:
I just wanted to share some of the initial tests of PSK and PSKR multiple carriers and I have to say I am pretty happy so far. I tested 2 x PSK500R and 3 x PSK500R and it is still pretty robust.I had definitely multipath reception in the waterfall and despite that I had very few repeats. 2 x PSK500R gives us 10% more speed than PSK500 but it **looks** more robust from today's observations, in a 1200Hz bandwidth.3 x PSK500R gives 55% more speed than PSK500 BUT at almost 4 times the bandwidth!I also tested 2 x PSK500 and that really flies with a 17174 bytes email document (text only) downloaded in 2 minutes 25 seconds from the receive of the FM command to the TX of the FA command. That is 7,107 characters per minute, in a 1200Hz bandwidth...not bad at all.Another way to look at it: that is 5.92 characters per minute per Hertz of bandwidth, **in real life, with QRM and block repeats**, not theoretical best case!The theoretical best case of 2 x PSK500 with a 1 seconds TX delay on both sides is 8,078 characters per minute net speed or 6.7 CPM/Hertz with the current ARQ overheads.If we increase the number of blocks of data per transmission to 16 instead of 8, we get a net speed of almost 9,400CPM. Then reduce the delay on each side to 1/2 second and we get over the 10,000CPM in the same 1200Hz bandwidth.I will also test the 4 x PSK500 and 4 x PSK500R on FM too and report.The next development steps will be to switch the "Nitrous Oxide ON" with 4 PSK and maybe 8 PSK.....I'll keep you posted. 73, John (VK2ETA)
