[GreenKeys] Changing speeds on a Lorenz Lo-15b

[Duncan Brown]

Jeff,

I'm sure you want the "challenge" doing this electronic speed control, 
but have you ever tried running your Lorenz on 45 baud? Or a 45 baud 
machine on 50 baud?  I have copied DDK off the air on a 60WPM TT-98 and 
copied 60WPM tapes on a 50 baud RFT T-63.

These machines were designed long ago to work on long (many miles) 
current loops with lots of inductance and capacitance distorting the 
waveform.  Knowing that there would be lots of distortion on the 
received signal, the selector mechanisms were designed to only use a few 
milliseconds of the data pulse to make the mark/space decision. They 
designed in the Range Finder adjustment to pick the best spot to make 
the mark/space decision. The Range Finder determines the delay after the 
start pulse to start reading the data pulses.

When receiving a good RTTY signal (and especially when receiving from 
ITTY, i-Telex, or Heavy Metal), you are starting with an almost perfect 
digital waveform and then traveling over only a few feet of wire to the 
TTY, so there is very little distortion. If you check your Range, it 
will typically be 80-100 points. that is a lot to play with.  If you set 
the Range low, the machine will start reading data sooner and a 45 baud 
machine will be able to copy (slightly) faster speeds like 50 baud. (The 
1st bit is read early, the 3rd bit is read in the middle and the 5th bit 
is read late.) Conversely, on a 50 baud machine, set the range higher, 
and you will be able to copy the slower 45 baud signal.

You will not have as much range copying this "wrong" speed, but 
generally you don't need much range with today's RTTY & Internet signals.

Have fun,

Duncan
K2OEQ


On 12-Dec-15 13:43, Jeffrey D Angus wrote:
> I've been discussing various methods of dealing with setting the speed
> on a Lorenz Lo-15b with Henning and Heinz.
> It's a governed motor and will it's simple to just fiddle with the two
> levers on the governor, it's not exactly a quick back and forth change.
>
> Now, Henning's pretty well got me sold on getting the i-Telex stuff and
> connecting the Lorenz to that. No problem. That runs at 50 Baud.
> But I also want to play with my HAL ST-8000A terminal unit and RTTY
> via Amateur radio. Yuppers, _they_ all run 45.45 Baud.
>
> Now one truly novel approach, Henning sent me a picture of where
> some clever person added a SECOND centrifugal governor switch to
> the back of the motor. Just flip a switch to select either one.
>
> I've decided on something a little more "electronic" method. A phase
> locked loop. Also, it's basically a going to be a "drop in" modification.
> Something anyone with a Lorenz machine can just wire in, in place of
> the centrifugal switch on the motor.
> I've ordered a bunch of bits and pieces to play with.
> Should have something up and running by the end of January.
> "Film at eleven" as they say.
>
> Jeff
>


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