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Author Topic: RTTY shift 170Hz?  (Read 8034 times)
AA4N
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Posts: 110




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« on: July 19, 2010, 08:54:47 PM »

Hi all,  I just finished my first successful digital QSO.  It was good fun.  I was running FSK RTTY with some rather old gear.

Special thanks to Dan NI9Y for answering me even though I had my mark and space reversed Smiley  I think I may have some other problems to iron out as well, apparently some of my numbers weren't coming across as numbers.

Dan pointed out that I was running a rather narrow shift at 170Hz and suggested that 200Hz was more common...(it's entirely possible that I misunderstood, I was fighting with lots of gear/software/pilot-error at the time).     I was under the impression that 170Hz was the common shift and 850Hz was the rather old fashioned wide option.

So, do I need to dig into the rig and tweak that FSK shift?  Just checking...

73, mike AA4N
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VA7CPC
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Posts: 2387




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« Reply #1 on: July 19, 2010, 09:36:19 PM »

170 Hz shift is standard.  It's the default for MMTTY (and probably every other RTTY decoder).   And it's what most stations use on the air.

I suspect that you misunderstood.

               Charles
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G0RIF
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Posts: 129




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« Reply #2 on: July 20, 2010, 12:08:51 AM »

As Charles said, 170Hz is standard.

It's not often you'll see 200Hz shift on the bands.

Regards,
Dean
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AA4PB
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Posts: 12854




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« Reply #3 on: July 20, 2010, 05:25:57 AM »

The 200Hz shift thing came about in during the multi-mode hardware TNC days. HF packet, pactor, and amtor used 200Hz shift so they saved circuitry by adopting it for RTTY on those units as well. 200Hz was a Bell modem standard and inexpensive ICs were available at the time.

Now that we are working with software its a simple matter to use the original RTTY standard of 170Hz shift for RTTY and 200Hz shift for modes where 200Hz is standard.
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