[RTTY] uh, what about spectrum?

[Michael Keane K1MK]

At 03:34 PM 1/16/06, you wrote:

>On Jan 16, 2006, at 12:03 PM, Michael Keane K1MK wrote:
>
> > the bandwidth that contains 99% of the energy i.e, the bandwidth
> > such that, below its lower and above its upper frequency limits,
> > the mean powers radiated are each equal to 0.5 percent of the total
> > mean power radiated by a given emission.
>
> >>> Section 2.202 of the FCC rules specifies that the
> >>> necessary bandwidth of an FSK signal is equal to
> >>> 1.2 x Shift + BaudRate.
>
>The problem is that the latter definition does not necessarily mean
>that the 1% power is maintained.  A poor keying waveshape in an FSK
>transmitter can lead to a much wider (as defined by 1% power) signal
>than specified under Section 2.202.

Maintaining it is covered by a different rule. 
:-) Cicks, splatter, poor pulse shaping, etc. 
that would cause one's signal to exceed the 
necessary bandwidth are not presently allowed and 
nothing being proposed would change that.

§97.307(a) states that no amateur station 
transmission shall occupy more bandwidth than 
necessary for the information rate and emission 
type being transmitted. The petition for rule 
making leaves §97.307(a) unaltered.

The(occupied) bandwidth of a signal is defined in 
§97.3(a)(8) to be the width of a frequency band 
outside of which the mean power of the 
transmitted signal is attenuated at least 26 dB 
below the mean power of the transmitted signal within the band.

What has been proposed is to remove the 26 dB 
below the mean power definition for bandwidth 
from Part 97 which would result in the definition 
of occupied bandwidth defaulting to the 1% 
definition that is provided in Part 2 of the FCC rules.

In both cases the determination of necessary 
bandwidth is as specified in §2.202.

Bottom line is that a 45.45 baud, 170 Hz shift 
RTTY signal must currently occupy a bandwidth as 
defined in §97.3(a)(8) of less than 250 Hz in 
order to comply with the letter of the exiting rules.

73,
Mike K1MK

Michael Keane K1MK
k1mk at alum.mit.edu