[GreenKeys] FSK converter madness

[Nick England]

That's exactly what military low-level signaling is. Hubbing repeaters and
+/- signaling everywhere.
Info here -
https://www.navy-radio.com/manuals/tty/tty_ctl-391-6010.pdf


Nick England K4NYW
www.navy-radio.com


On Sat, Jul 6, 2024 at 12:35 AM Jim Haynes <jhhaynes at earthlink.net> wrote:

> On Fri, 5 Jul 2024, Harold Hallikainen via GreenKeys wrote:
>
> > Following up, issues like this is why I really like having a terminal
> unit
> > act like a Teletype. It should be able to key a floating loop and sense
> > the current in a floating loop. An external loop supply with all
> equipment
> > (KSR printer, TD, Reperf, and TU) have the same interface to the loop.
> >
> > Harold
> > https://w6iwi.org/rtty/DspTU2/
> >
> And this has been one of the intellectual challenges of the last 2/3
> of my life.
>
> On the one hand, we would like to have things run on 60 ma loops so we
> can just plug in standard TTY gear and have it work like it did in
> history.
>
> On the other hand, putting things in loops makes simple things more
> complicated, like you have to use closed-circuit jacks for all the loops,
> and you have to have dummy loops to keep machines from running open
> when they aren't being used.
>
> So if I were designing a set from the ground up I would have every
> selector magnet use a solid-state driver, input voltages something
> like RS-232 or MIL-STD-188, and selector magnet drivers biased so
> that with the input not connected to anything the selector magnet
> is held marking.  Every keyboard or tape reader would likewise be
> hooked up to generate the low-voltage signals.  You have one or more
> signal hubs, and everything can send into a hub and everything can
> receive from a hub.  (Using gates so with multiple senders any one
> of them can drive the hub to spacing.)  The low voltages can easily
> be interfaced to electronic gear, so if you want to stick in a solid
> state speed converter or a regenerative repeater it is duck soup.
>
> I would insist on bipolar voltages like RS-232 or MIL-STD-188 because
> in a radio setup there is RF floating around and it will be rectified
> by all kinds of devices such that you don't get zero volts when nothing
> is happening but the transmitter is running.
>
> Many years ago I built my station along these lines, at first using
> tubes since we didn't have any good high voltage transistors at the
> time to use for selector magnet drivers.  Later I moved to a modified
> RS-232 scheme when we got good transistors for the purpose.  But I
> never got very far with it because I'm lazy and it was too much work
> to build all those selector magnet drivers and I was constantly needing
> more of them.  And I was somewhat more interested in having a historical
> kind of installation where the 60m loops were part of the scheme.
>
> Things were complicated by irv Hoff's insistence that you should always
> be able to plug in a keyboard and printer in series into a loop and
> have everything work.  I did some work on a "leg combiner" which could
> take a keyboard and printer in series and tell the difference between
> signals generated by the keyboard and signals coming from outside.
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