WICEN Vic: Using the Yaesu SCU-17 Interface Unit with Winlink Express / VARA-HF

[John & Bronwyn]

This note applies mainly to those operators who wish to use an older 
radio with the Yaesu SCU-17 Interface Unit to run Winlink Express using 
VARA-HF.

Some brief explanations:

.  The SCU-17 connects to a computer via USB and provides a sound card 
for digital mode Tx and Rx audio, plus a RS-232 radio control port to 
set frequency, mode, etc, plus another RS-232 port for PTT or FSK 
keying.  The RS-232 control port may require a further adapter for use 
with your radio, to adapt to CAT, CI-V or whatever radio control system 
your radio uses.  The SCU-17  can be used with a wide variety of 
programs for "soundcard" digital modes.

.  Winlink Express / VARA-HF provides messaging, email and file transfer 
over HF radio and is one of the two preferred WICEN digital systems for 
HF.  The other is EmcomWin and Pactor.

.  VARA-HF is a good "soundcard" data mode which plugs into the Winlink 
Express software.  Although not quite as robust as Pactor, it is far 
less costly, and performs much better than earlier "soundcard" modes 
such as Winmor and ARDOP.

The problem is, that Winlink Express / VARA-HF will not work with the 
SCU-17 "PTT" RS-232 port.  When it attempts to open the port, it returns 
an error message that "the port may be in use by another program".   It 
isn't.  The problem is due to an incompatibility between Winlink Express 
and the "PTT" RS-232 port in the  SCU-17.  The Winlink organisation is 
aware of the issue but other issues have higher priority for attention.

With most newer radios, the "PTT" port in the SCU-17 is not required 
because Rx/Tx switching is actually controlled using the radio control 
port (CAT, CI-V, or similar).

For older radios which require PTT, there are two possible workarounds.  
The first is to use the VOX function in the radio, provided this will 
operate from the radio's DATA port.  However some radios use the PTT via 
the DATA port to switch the TX audio from the microphone to the data 
input.  VOX won't work with these radios.

The other workaround is to use a separate RS-232 port for the PTT 
control, via a USB / RS-232 dongle and an optocoupler for isolation, and 
just ignore the second RS-232 port in the SCU-17. This is a bit 
inconvenient but works well.

I hope this helps anyone who wants to use the SCU-17.  Apart from the 
issue outlined above, which only applies to Winlink Express / VARA-HF, 
it works very well.


Cheers,   John VK3ZRX