Not to ignore the regulatory aspect, but on a technical note:
Correct me if I am wrong but wouldn't sending a CW ID simultaneously with message tones require linear amplification to produce an acceptable signal? Many use nonlinear class D and E amplifiers on LF and MF. Actually I suspect the vast majority do.
73, Paul N1BUG On 9/28/20 9:41 AM, David Tiller wrote:
Thanks, Joe, K1JT, Steve, K9AN, and Bill, G4WJS for all your hard work and these new modes. I don't want to be a stick in the mud and I am not trying to stir the pot, but is there any issue with modes that transmit for >= 10 minutes and the US requirement to ID at least every 10 minutes? I don't think part 97.119 addresses IDs that take longer than 10 minutes. I admit I don't fully understand all of the details of the transmitted data in FT4/FST4, so if I'm off-base, please forgive me (and kindly correct me!). If the FEC employed spreads the callsign bits out over the message, then my analysis is incorrect from the git-go. For FST4, if the message bits are symbol-encoded and transmitted in the order as shown in the QEX Article on FT4 [See QEX 2020 Jul/Aug, page 7] and assuming the sender's callsign is sent as the second c28 call, it looks like in most cases the sending callsign is within the first 57 bits of the 77 bit raw message. That means that 57/77 = 74% of the raw message has to be transmitted before the sender's callsign is transmitted. That means the longest transmission that gets the sender's call in at/under 10 minutes is about 13.5 minutes or 810 seconds. If I have the callsigns backwards, then the sender's call is sent first in most cases. That makes the longest transmission more like 27.5 minutes, but then the last 17.5 minutes of the transmission are unidentified (barring FEC repetition of the callsign bits). That means the longest tx in this case would be 20 minutes - The first 10 are identified in the message and the last 10 would be identified by an explicit ID by the operator. I know this won't be a popular idea, but adding a low power CW ident at a standard (low, perhaps sub 100 Hz) frequency in addition to the transmitted signal every 10 minutes would unquestionably address this. Remember that the requirement is for each station to ID, not to ensure that the ID doesn't clash with other ID transmissions. If every FST4 signal over 10 minutes id'ed via CW on VFO + 50 Hz, say, that would be sufficient to satisfy 97.119. Ideas/comments? Again, I'm just asking the question, please don't shoot the messenger.
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