[Elecraft] K3 Filters for digital work

[Joe Subich, W4TV]

> IMHO, RTTY is like AM -- a classic mode which uses more bandwidth
> than necessary, but is nice to keep around for nostalgia and to
> relive history.

RTTY is not like AM in using more bandwidth than necessary.  *ANY*
FSK signal will have a minimum bandwidth (as defined by ITU) of
(1.2 * shift + baud rate).  For 45.45 baud, 170 Hz shift (traditional
RTTY) that works out to about 250 Hz

73,

    ... Joe, W4TV


On 11/27/2013 2:00 PM, Bill Frantz wrote:
> I have a 250 Hz filter I use for PSK and RTTY. It helps when there is a
> strong nearby station that overloads the AtoD converter between the K3
> and my computer. During a RTTY contest, I found it helped, but the dual
> frequency DSP RTTY filter was more than enough for most contacts.
>
> When I use the filter with PSK, I lose the computer waterfall and the
> computer noise reduction because of the narrow bandwidth. I use full
> bandwidth to scan for signals and the 250 filter after establishing
> contact. Usually a narrow filter works better than the computer noise
> reduction.
>
> I would worry about 200 Hz for RTTY. While the deviation is nominally
> 170 Hz, there is energy out wider than that which may be affected by the
> skirts of the 200 Hz filter.
>
> IMHO, RTTY is like AM -- a classic mode which uses more bandwidth than
> necessary, but is nice to keep around for nostalgia and to relive history.
>
> Cheers - Bill, AE6JV
>
> On 11/27/13 at 9:58 AM, recordupe at verizon.net (Dave Barr) wrote:
>
>> Which two of the 200/250/400 and 500 hz filters are best for digital
>> use, primarily RTTY, both contests and dx.  I understand that for
>> JT-65 and PSK the standard ssb filter, or even the AM filter is
>> useable.  I am concerned that the 200 hz might be too narrow for
>> RTTY.  I work some CW but almost no ssb.
>
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