[RTTY] MMTTY Tx Tab settings

[Joe Subich, W4TV]

 > What do each of these do and what are the optimum settings?
 > Tx BPF check  box               [default  = Selected?]

Enables a bandpass filter in the AFSK output.  The bandpass filter
removes distortion products and harmonics.

 > Tx LPF check  box                [default  = not Selected]

Enables a lowpass filter in the AFSK output.  The lowpass filter
removes harmonics, it does not impact distortion or switching
transients.

Note: these filters only act on the audio generated by the sound
card.  They do not remove distortion/harmonics generated by
running the sound card at maximum output level (clipping in the
analog output) or over driving the input of the transceiver. Nor
do they remove hum caused by improper grounding/bonding of the
computer soundcard, interface, and transceiver.

 > Tap (range 24-512)           [default = 48]

Controls the steepness of the filter skirts.  Full details is an
in depth topic on the mathematics of digital signal processing.

 > Freq in hz (range 40-600)    [default = 100]

Controls the width of the bandpass filter.  Note: with high tap
numbers (steep sided filters) the bandwidth should be *greater than*
400Hz to prevent loss of "sharpness" in the mark/space transitions.

73,

    ... Joe, W4TV


On 4/26/2017 9:00 AM, Kermit (aka Ken) via RTTY wrote:
> I'd like some info on setting parameters in the TxBPF/TxLPF box in  the
> MMTTY TX Tab section .
>
> I can't find good documentation in the MMTTY help file.  There has  been
> some discussion here recently.
>
> The parameters and their apparent default settings (from  most Profiles)
> are:
>
> Tx BPF check  box               [default  = Selected?]
> Tap (range 24-512)           [default = 48]
> Tx LPF check  box                [default  = not Selected]
> Freq in hz (range 40-600)    [default = 100]
>
> What do each of these do and what are the optimum settings?
>
> Thanks & 73,
> Ken, AB1J
>
>
>
> In a message dated 2017-04-25 2:18:13 P.M. Coordinated Universal Tim,
> lists at subich.com writes:
>
> On  4/25/2017 10:04 AM, Ed Muns wrote:
>>  Set MMTTY taps to 512  too.
>
> AND *check* TxBPF (TX tab) it is not checked by default.
> TxBPF  is not needed for FSK and increases the processor
> load (for marginal  systems) on AFSK.
>
> You will also want to set Freq (bandwidth) to 600 Hz  (or
> enter 400 Hz manually).  300 Hz is too narrow with  512
> taps.
>
> 73,
>
> ... Joe, W4TV
>
>
> On  4/25/2017 10:04 AM, Ed Muns wrote:
>> AFSK on the K3/K3S is fine with low  tones if the radio AFSK TX filter
>> is enabled. Set MMTTY taps to 512  too. Make sure to set the same
>> audio  tone pair in both the radio  and MMTTY.
>>
>> 73,
>> Ed  W0YK
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