Andy, **However, if ALE-400 ARQ is getting through with error free throughput, what are the chances that Olivia or Thor or some faster mode is getting through with much faster throughput and a only a few errors ? Other than a wider bandwidth, the other mode may turn out more efficient.**
That's a good question. If you first start by configuring Olivia and Thor to match ALE-400s 60 wpm speed, you wind up with three modes that have similar minimum signal-to-noise figures and more or less the same robust HF channel characteristics. Running faster versions of Olivia or Thor to surpass ALE-400's speed would decrease the robust quality of those modes even further causing an even greater number of throughput errors. At that point it comes down to whether the print is still readable with the non-ARQ modes under the conditions you mentioned. It's probably a bit simplistic, but I believe the ARQ in ALE-400 can have an advantage over other modes in an apples-to-apples comparison because it constantly checks for throughput errors every few seconds and corrects them as it 'rides' the band changes. When you compare this to non-ARQ modes with similar HF channel characteristics, you realize that a lot of print can be sent by a long-winded operator who is unaware that a large percentage of his message is not making it through; until he turns it over. By that time it's too late and the message needs to be repeated. With ALE-400, checks and balances are made in a matter of seconds for error-free print. Another unique aspect of ALE-400 is it's bilateral operation. Since both stations can type at the same time, text from each station passes back-and-forth ever few seconds allowing the conversation to change directions quickly if need be. The bilateral wpm rate is 85 wpm or 42wpm each way; the standard is 60 wpm unilateral. *I'm waiting for a development where some sort of hand shake or RS-ID initiation at the beginning of a QSO establishes the current SNR. Then on your screen up pops a messages that says... "based on the SNR of -11dB THOR11 is recommended, do you want to switch " ? That would be something Andy. Tony -K2MO
