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Write down what the count lag and the symbol count measure

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The third probe run puts numbers on both. TxBufLen lags by 100 to 150 ms, about
one character at 45.45 baud: twenty-one characters pushed at 2496 ms read 0 at
2497, 2547 and 2597, then 26 at 2647. It moves once per symbol transmitted, so
readings 50 ms apart repeat.

It read 26 for 21 characters because it counts Baudot symbols, and the message
carried two digits: a shift to figures and a shift back each time, plus one at
the start. That is the case the cap was needed for and I had not seen. A contest
exchange is mostly digits, so the engine always has more to transmit than the
clock thinks, and the clock alone would run ahead of it on every QSO.

Slack of three characters covers both, so nothing changes in the pump. The
count reaching 0 does not cut the end of a message off either: it emptied 350 ms
before the last character was decoded back and the engine held the transmitter
up for another 900 ms.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RtspmWmS7f8kUvcyaHpRWZ
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ericek111
2026-09-01 23:20:11 +00:00
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@@ -65,9 +65,16 @@ a sound card:
|---|---|
| Does the control answer `TxBufLen`? | Yes, and a name it does not know fails with `DISP_E_UNKNOWNNAME`, so the two are distinguishable. |
| What does it count? | Characters left to transmit. Seventeen were pushed; a second later, with five decoded back off the air, it read 12, and it counted down to 0 as the message went out. |
| How current is that number? | Not current. Read a millisecond and again fifty milliseconds after twenty-one characters had been pushed — and were already going out, the first of them decoded back a moment later — it still said 0. So a pump that fed on the count alone would hand over a whole message in half a second and put all of it beyond reach. How far behind it runs has not been measured; the probe now writes down every reading for the two seconds after a push, which is where the number will come from. |
| How current is that number? | It lags by 100 to 150 ms, about one character at 45.45 baud. Twenty-one characters pushed at 2496 ms read 0 at 2497, 2547 and 2597, then 26 at 2647. That is why the count cannot be the pace: a pump that fed on a fresh 0 would hand over a whole message in half a second and put all of it beyond reach. |
| What is it counting? | Baudot symbols, not the characters handed over. Twenty-one characters read as 26, and the message was `CQ TEST DE OM5M OM5M `: two digits, each needing a shift to figures and a shift back, plus one shift at the start. It also only moves once per symbol transmitted, so four readings 50 ms apart are the same number. |
| Does a backspace take back a character the engine has not transmitted? | No. Pushed in as a character it made the count go **up** by four, and the text went out unchanged. MMTTY's help describes its backspace key doing this in its own window; through `PostMmttyMessage(4, 8)` it is just another character. So text in the engine cannot be retracted, only aborted. |
| Way to send | This engine is set to Character out: `ABCD` with no space after it went out at once, a character every 200 ms. MMTTY's help says Word out is the usual setting, which would hold that word, so the pump copes with both. |
| Way to send | This engine is set to Character out: `ABCD` with no space after it went out at once. MMTTY's help says Word out is the usual setting, which would hold that word, so the pump copes with both. |
| Does the count reaching 0 cut the end of a message off? | No. It reached 0 about 350 ms before the last character was decoded back, and the engine held the transmitter up for another 900 ms after that, so `{RX}` straight after the count empties does not truncate anything. |
Counting symbols rather than characters is what makes the cap earn its place. A
contest exchange is full of digits, so the engine has more to transmit than the
pump's clock thinks: `599 001` is seven characters and eleven symbols. The clock
would run ahead of the engine on every exchange; the cap is what stops it.
The report is worth reading for the receive side as well. With MMTTY's sound
loopback off, its help says the receive window is fed from the transmit window,