[GreenKeys] HAL RVD-1002

[Harold Hallikainen]

Those are RS232 levels. I designed a loop to TTL interface (
https://w6iwi.org/rtty/tu300/Tu300LoopDriverSchematic.pdf ) that fits in a
USB dongle case to plug into the back of a Flesher TU-170A or TU-300. TTL
to RS232 conversion could be done with an MC1488 (transmit) and MC1489
(receive) or a MAX232 (
https://www.analog.com/en/products/max232.html#part-details ) which
includes charge pumps to generate the higher positive and negative
voltages.

Is the RVD-1002 transmit and receive, or, perhaps, receive only? If
receive only, U1 in the above linked schematic could pull the RS232 line
towards -12V when in mark, and a pull-up resistor could pull it towards
+12V when in space. That would be a minimum parts count (the ideal design
has zero parts) design, I think. In the above linked schematic, Q1 acts as
an inverter taking the mark low output of U1 and converting it to mark
high going into the TU-170. For RS232, you would not need this inversion.

To key the loop from RS232, K1 could be used with pin 1 grounded, and the
RS232 transmit line driving U1 through a current limit resistor.

Good luck!

Harold
https://w6iwi.org


On Sat, December 7, 2024 11:23 am, Eric Moore wrote:
> Hello! I am trying to set up a HAL RVD-102 with my TD.
>
> The RVD-102 takes a mark bit of -5 to -15V and a space bit of +5 to +15V
>
> I do not have the optional loop interface. I suppose to use this with my
> model 14 TD I would need to build a circuit to take 100V/0V and convert to
> 10V/-10V or similar, correct? (AKA low voltage serial)
>
> Also, I have a Xitex UDT-170, but no manual. Anyone seen one before?
>
> Thank you,
>
> -Eric
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