[GreenKeys] 7.00 vs 7.42 unit code

Wed Aug 7 14:40:32 EDT 2019

Thanks to John (and Jerry in pm) pointing out the key element to my
misunderstanding. The printer receive shaft is actually running at 420 opm,
which at 45.45 baud is equivalent to a 6.49 unit code (70 wpm).

So the printer in a 7.42 machine can handle a 7.00 stream OK as long as the
baud rate is the same.

The key is that the transmitter (keyboard or TD) has to be geared correctly
for a 7.00 unit code or 390 opm for 45.45 baud.

Nick, typing at about 12 opm on his phone.

On Wed, Aug 7, 2019 at 2:02 PM John, W9DDD <w9ddd at tapr.org> wrote:

> OK, I did the calculations on the gear ratios.  The receive shaft speed
> for 7.42 nominal 60 wpm is 420 rpm.  The receive shaft speed for 7.00
> nominal 65 wpm is also 420 rpm.  And the selector cam for both 7.42 and
> 7.00 is the same, so it outta work both ways.  Now, that's theory, in
> practice YMMV, although I don't know why. Worn selector clutch?
>
> John, W9DDD
> Ich habe dreimal abgeschnitten uns jetzt zu kurtz. (I cut it off 3 times
> and it's still too short.)
>
> On 8/7/2019 10:46 AM, John, W9DDD wrote:
> > I checked the parts section and it only shows two choices for the
> > selector cam.  5 level and 8 level.
> >
> > John, W9DDD
> > Ich habe dreimal abgeschnitten uns jetzt zu kurtz. (I cut it off 3 times
> > and it's still too short.)
> >
> > On 8/7/2019 10:36 AM, John, W9DDD wrote:
> >> Everything you say sounds right.
> >>
> >> I've suspected that the RX shaft ends up going at the same rate for
> >> 7.00 and 7.42 and 7.50 as long as it's 45.45 baud, but I've never
> >> taken a set of gear specs to do the math.  What makes me suspect that
> >> is I think the selector cam is the same.  I read too many manuals and
> >> then hit information overload.
> >>
> >> I have a 7.00 keyboard that I can eventually use to send to a 7.42
> >> printer.  Wonder if the repeat key results in full speed?  Or I could
> >> buy that LXD31 on epay.
> >>
> >> John, W9DDD
> >> Ich habe dreimal abgeschnitten uns jetzt zu kurtz. (I cut it off 3
> >> times and it's still too short.)
> >>
> >> On 8/7/2019 9:41 AM, Nick England wrote:
> >>> Doing some machine shuffling this week made me think about this -
> >>> please steer me back on course if my thinking is off.....
> >>> Truth-
> >>> 7.42 unit code has a start bit and 5 data bits of equal length (1.00
> >>> unit each) and a stop bit 1.42 units long.
> >>> 7.00 unit code has a 1.00 unit stop bit.
> >>> 45.45 baud code can be either - each 1.00 unit data bit is 22ms.
> >>> So 7.42 unit at 45.45 baud is 60 wpm
> >>> and 7.00 unit code at 45.45 baud is 65 wpm
> >>> There's a chart at http://www.navy-radio.com/tty/speed-feed.gif
> >>>
> >>> Consequences-
> >>> These two do require different gear sets - you can't just put 60wpm
> >>> gears (368 opm) into a 7.00 unit machine (390 opm) - that would make
> >>> the baud rate wrong and your selector and keyboard transmitter timing
> >>> would be off.
> >>> A 7.00 printer can copy a 7.42 keyboard or 7.42 TD no problem.
> >>> A 7.42 printer can copy a 7.00 keyboard if you don't type at max rate
> >>> A 7.42 printer probably cannot copy a 7.00 TD
> >>>
> >>> What about sending RTTY with a 7.00 keyboard or TD? - will the
> >>> computer software RTTY folks copy it OK? I assume so, but don't know
> >>> for sure.
> >>>
> >>> Comments welcome.....
> >>>
> >>> best regards,
> >>> Nick England K4NYW
> >>> www.navy-radio.com <http://www.navy-radio.com>
> >>>
> >>>
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-- 
Nick England K4NYW
www.navy-radio.com
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