[RTTY] uh, what about spectrum?

[Michael Keane K1MK]

> At 14:15:22 EST 16, Jan 16 2006 Kok Chen wrote:

> >> Section 2.202 of the FCC rules specifies that the 
> >> necessary bandwidth of an FSK signal is equal to 
> >> 1.2 x Shift + BaudRate.
> 
> Neccessary bandwidth is that is required for you to
> transmit and   receive an RTTY signal.

In this case what's important is that necessary bandwith (as this term is defined elsewhere in the FCC rules) is the bandwidth that appears in the table of authorized modes under the proposed rules.

2.202 (c) of the FCC rules specifies how necessary bandwidth is to be determined.

For an extising mode like FSK the FCC rules allow for the necessary bandwidth to be determined using the formula given in a table in 2.202(g). This table is a repeat of a table from ITU-R. 

This is a purly regulatory concept for how to assign a necessary bandwidth label to an emission mode, not necessarily something that corresponds to a measurable property of any real signal.

> How much must a signal be down at the bandwidth limits
> under the new  proposed rules?

Necessary bandwidth is defined as an integral quantity.
There's no definition of necessary bandwidth in terms of the points at which the signal is X dB down from its peak or average. 

If you want to compute necessary bandwidth by an alternative method then its 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.

> Does anyone have the precise rules of what baud rate 
> and what shifts are allowed under current regulations?

Below 10m: symbol rate <= 300 bauds; shift <= 1 kHz.

73,
Mike K1MK
--
Michael Keane, K1MK
k1mk at alum.mit.edu