Hi Andy, well, I don't agree... as soon as you talk efficiency, you have to define what that means.
For me bandwidth efficiency is 3-dimensional, it defines how much information can be transferred within a certain time span, within a certain bandwidth. JT65A works with 65 frequencies, which are 2.7 Hz apart. So its bandwidth is 175, add to that 2 guard bands if you want to put a different mode close to it on both sides... You can put 2 JT65A signals very close together, because it uses a pseudo-random algorithm to make sure 2 JT65A signals (almost) never use the same concrete frequency at a certain point in time. As such it is quite bandwidth efficient. That changes completely when you would put a PSK signal that close, it would not work anymore. BTW, the comparison I showed was real... PSK500 has a raw speed of 48 CPS, and the net ARQ speed, including arq repeats is 23 CPS. Of course I cannot do it with 100 mW / 1000 Miles all the time, I need 5 Watts for an average connection. On 80m I have a stable connection to DA5UWG during daylight time using PSK500(down)/PSK500R(up). During the night I need MFSK32(down)/THOR8(up) for the same path... Nice thing abt PSkmail 1.0 is that you can start the connect in MFSK16, the system will decide to upgrade the speed/mode when possible, so you work in the most efficient mode most of the time. And BTW, it helps to use modes close to 500Hz bandwidth (PSK500, MFSK32, THOR22) when you use a 500 Hz (matched) filter :) Just wanted to express that looking at problems 1-dimensionally hardly ever reveals the full truth... 73, Rein PA0R Good point. What you have defined , Rein,is the occupancy efficiency in terms of time.. I was measuring efficiency in terms of bandwidth used. Obviously the othe r measure is wether the message was deleivered. Using 5 watts for a 300-400 miles trasmission on 80M at night , PSK250 may have needed sveral repeats to send 13 chracters . So even in term so time PSK250 may have been close to 0.001547619 . I'll do a test tonight. Andy K3UK
