While this information does not seem to support the SCS claim of working way down to the minus teens of db S/N, it is interesting that in the "old days" Pactor 1 users claimed that they could get throughput when they could not even hear any suggestion of modulation.
I never found this to be true, but then I never had any SCS products either. Having an SCS Pactor 1 modem on each end of a connection was supposed to work much better than with mixed or other brands of modems. Particularly because of the ability to do memory ARQ. One thing that seems to escape Pactor 3 users, is that even though it might work 3 to 5 times faster than Pactor 2, the bandwidth is about 4 or 5 times wider so there is no real benefit if you are comparing occupied space to bandwidth. Sharing a finite and non-channelized service such as we radio amateurs use, having many small bandwidth users means more throughput for more users than one large bandwidth user at a time. 73, Rick, KV9U DuBose Walt Civ AETC CONS/LGCA wrote: >If you looked at the PDF document of KN6KB's measurements, that is what is >showes. > >The only difference between Pactor I, II and III is the throughput >(NetByte/minute) at various SNRs. > >I can only assume that the BER or percent of errors ( zero errors?) was also >the same. > >PIII +10 dB SNR +5 dB SNR 0 dB SNR > -5 dB SNR >Throughput 11,500 NB/min 9,000 NB/min 4,000 NB/min 200-300 NB/min >PII >Throughput 3,200 NB/min 2,500 NB/min 1,800 NB/min 200-300 NB/min >PI >Throughput 900 NB/min 900 NB/min 600 NB/min > 100 NB/min > >All these are what I see on KN6KB's chart. > >At each of the above SNRs the Pactor mode has a shown throughput. > >If need 9,000 NB/min at a +5 dB SNR, then you need Pactor III. But if you >only need a maximum throughput of 800 NB/min at +5 dB SNR, then you only need >Pactor I. > >Walt/K5YFW > > >
