[RTTY] ARRL Bandwidth Proposal

[Peter Laws]

On 4/14/05, Kok Chen <chen at mac.com> wrote:
> On Apr 14, 2005, at 8:41 AM, Peter Laws wrote:
> 
> > I did read it - thanks for the link.  I should know this, but since
> > I'm at work, apparently I've forgotten: What is the bandwidth of a 170
> > Hz-shift RTTY signal?  It's more than 170 Hz, but by how much!?
> 
> With AFSK, you can experiment with different transmit bandwidth
> rather nicely.  I have found that a moderate brick wall output filter
> with about 350 Hz bandwidth to not interfere with the performance of
> RTTY.

... 

> If you include the third harmonic, that makes the half-width of the
> mark and space "lines" to be about 70 Hz.  Quick back-of-the-envelope
> therefore gives 170 + 2*(70) = 310 Hz.

OK, so we can safely say, then, that the BW of RTTY is "about" 310-350 Hz.  

Looking at the EC's proposed bandplan
(http://www.arrl.org/news/stories/2005/04/13/1/?nc=1), it appears that
the 500-Hz threshold is at about the same place as the traditional
bottom of the RTTY sub-bands, i.e. about 65-80 kHz above the bottom
(10/12/17/160, being excepted for various reasons).

I could have sworn the numbers were different when I looked this
morning, but it appears that RTTY ops only lose the new Pactor robot
email sub-bands, if I'm reading this right.  And it *appears* that we
gain all spectrum above the 500-kHz threshold, tho' I can't believe
that will actually happen.


-- 
Peter Laws | N5UWY/9 | plaws0 gmail