Re: New DSC user

Richard Ware

On Thu, 14 Feb 2019 at 01:05, Chris Black <n1cp@...> wrote:

I am using an Icom 7300 RTTY mode with Wellbrook 1530LN antenna and have had no trouble with Navtex and DSC with SeaTTY but having trouble getting DSCDecoder to work.
Hello Chris and welcome to the group.

I'm the other side of The Pond to you but I do use DSC decoder and
SeaTTY. Both of them work perfectly, and I'd suggest SeaTTY has the
edge over DSC decoder on MF and HF DSC.

Let's assume you want to monitor 8414.5 Kc/s
My receiver is set to USB mode and 8413.25 Kc/s, giving an offset of
1250 c/s (we old-timers don't do Hertz!).
On DSC decoder, in the VIEW > SPECTRUM window you need to make sure
that the red horizontal line is centred on 1250 c/s. If it isn't,
you'll need to click on the red line, see what the reading on the
right-hand side of the window says, and use the cursor to adjust the
line so that it DOES show 1250 c/s. You can of course choose any
offset you like within reason. 1700 c/s is what the maritime world
uses so in that case your receiver would need to be in USB mode and
tuned to a frequency 1700 c/s below the assigned freq (e.g 2185.8 for
2187.5 Kc/s) and the red line on DSC decoder would need to be centred
on 1700 c/s
I tend not to use the auto-tune facility. As for the demodulator,
under OPTIONS > demodulator I've selected 'Alternate HF modem' but
left the other options unticked.

I'm taking a guess here and saying that you need to set the decoder to
work with inverted tones.
Click the MF/HF and select 'inverted tones'
In that window you should also see the value of your offset displayed

I can remember talking someone through the setting-up procedure for
DSC decoder (even though it's adequately described in the HELP file).
He was getting nothing on the screen but was convinced the decoder was
set up correctly. It was, but he'd accidentally hit the vertical
scroll bar and was looking halfway down the screen where there was no
text. All the text was at the tiop. He ran the scroll bar back to the
top and there were the messages.

Anyway, give it a go and see what happens. If it doesn't, sing out and
we'll see if we can see if Plan B works. I may have forgotten

Ah, one last point. Don't overcook the audio in. Keep it low enough so
that the signal doesn't show any distortion. Again, this is mentioned
in the HELP file

Dorset, UK

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