[RTTY] UPDATE Re: FSK Keying

[Kok Chen]

> On Feb 26, 2018, at 10:45 AM, Ed Muns <ed at w0yk.com> wrote:
> 
> Most users are unaware and don't change
> the default.  And, why should they change it?  By leaving it wide, they keep
> their neighbors away from their operating frequency!

Psst.... don't tell them that a narrower transmitted signal is easier for the other end to copy too, Ed.  I.e., you will be asked for fewer repeats.

Practically all (well perhaps not MMTTY) RTTY demodulators today use very narrow tone filters, of the order of 50 Hz FWHM.  The extra keying sidebands are just wasted power that is thrown away by the demodulator anyway.  If you transmit 1 kW, some of it is simply wasted because the receiver is not even looking at the keying sidebands (unless the other end is using RITTY, which uses FSK Matched Filters).

We are lucky today that many, if not the majority, of hams have a panadapter whose resolution is better than 30 Hz.  Virtually everyone can see the wide signals for themselves.  Back in the beginning of the century, it was almost impossible to convince anyone that FSK is unnecessarily broad.  The following was written in 2005 a month before I retired (!):

http://www.w7ay.net/site/Technical/RTTY%20Sidebands/sidebands.html

73
Chen, W7AY