[RTTY] GRITTY 1.2 Filter Width

[Alex, VE3NEA]

Hi Hank,

GRITTY has a built-in pair of DSP filters with a bandwidth of about 25 Hz, and a carefully designed response. If you change the 
bandwidth in your radio from 3 kHz to, say, 300 Hz, you do not really improve overall filtering, but you make estimation of the 
noise floor more difficult. Selecting a narrow filter in the receiver in order to reduce interference does not make any sense, 
however, other effects, such as AGC pumping and audio clipping in the radio, may also play an important role, and narrowing the 
filter may help mitigate them. This is, of course, radio-specific. RTTY Skimmer Server that uses the same decoder as GRITTY 
works happily in the 96 kHz bandwidth.

One of the most important things that need to be tested is how GRITTY, and other decoders, perform in the major contests using a 
3 kHz filter with different transceivers. Maybe it's time to go wideband, at least with some radios.

73 Alex VE3NEA






On 2015-04-15 11:49, Hank Garretson wrote:
>
> Good Morning Alex,
>
> Thanks for advancing the state of the art.
>
> Help please.
>
> Let's say I use a 3 kHZ filter in a contest. Stations are packed together like sardines. I properly tune and center my station
> of interest. Will GRITTY pull my station out and ignore the adjacent stations?
>
> 73,
>
> Hank, W6SX
>