[Elecraft] K3 RTTY spectrum

[Joe Subich, W4TV]

 > Essentially AFSK will need to be used the same as FSK, tuning not
 > mousing.

As it should be ...

> With AFSK TX = FIL OFF you can wander around the waterfall if you
> wish. Not necessarily the best idea for the reasons given by Joe.

Among other reasons for *not* using wideband transmit and mousing
around the waterfall, take a listen to some of the signals on JT65
or JT9 ... many of them have high levels of broadband noise from
their sound cards that may be only 15 or 20 dB below the tone.
That noise is also attenuated significantly by the AFSK TX filter
resulting is a much cleaner signal (and significantly less QRM).

73,

    ... Joe, W4TV


On 2014-06-09 10:52 AM, Mike Harris wrote:
> Not a universal truth.
>
> The AFSK TX filter is centred around your selected tone (pitch)
> frequency pair.  You will have to tune each RTTY signal you wish to call
> with the VFO.  Meaning you cannot leave to K3 tuned to one frequency and
> wander around the waterfall picking off stations by using for example
> the MMTTY NET function.  It only takes around +/- 300Hz offset from the
> normal tone pair and your TX output has gone, evidenced by loss of RF
> output and a vanished ALC reading.  The K3 knows nothing about the
> actual tone pair being passed to it other than what we tell it.
>
> Essentially AFSK will need to be used the same as FSK, tuning not mousing.
>
> With AFSK TX = FIL OFF you can wander around the waterfall if you wish.
>   Not necessarily the best idea for the reasons given by Joe.
>
> If I remember correctly the NCJ article showed that at the the time of
> writing the K3 AFSK TX spectrum was cleaner than that of FSK.  I believe
> it also mentioned that Elecraft was tweaking the waveform to improve the
> FSK spectrum.  I no longer have the article so cannot confirm this and
> apologise if this statement is incorrect.
>
> Regards,
>
> Mike VP8NO
>
>
>
> On 09/06/2014 10:01, Joe Subich, W4TV wrote:
>>
>> On 2014-06-09 6:40 AM, Ken Chandler wrote:
>>  >
>>> I think I'm right in saying, you cannot use this filter if your
>>> running AFSK and 2tone !!
>>
>> Not true!  If one is running AFSK *always use AFSK A* and set
>> CONFIG:AFSK TX = FIL On.
>>
>> The AFSK TX Filter cleans up any hum on your sound card from bad
>> connections, grounding issues, or distortion from over drive.  However,
>> with the K3 one can get the same narrow transmit spectrum by using FSK
>> without the issues of AFSK.
>>
>> 73,
>>
>>     ... Joe, W4TV
>>
>>
>> On 2014-06-09 6:40 AM, Ken Chandler wrote:
>>> Kjeld et al
>>> I think I'm right in saying, you cannot use this filter if your
>>> running AFSK and 2tone !!
>>>
>>> Ken.. G0ORH
>>>
>>> Sent from my iPad
>>>
>>>
>>>> On 9 Jun 2014, at 11:01, "Kjeld Holm" <kh at kh-translation.dk> wrote:
>>>>
>>>> For the RTTY people,
>>>> You may all know already but I did not - therefore this info.
>>>> In ARRL National Contest Journal September/October 2013 issue on page
>>>> 3 to 7
>>>> the article RTTY Spectrum Measurement is discussing bandwidth issues
>>>> and
>>>> other issues regarding transmission of RTTY. For the ones of you who
>>>> have
>>>> access to this publication: Read it. For others the conclusion is as
>>>> I read
>>>> it: Switch on the AFSK TX filter in the Config menu (page 53 in the K3
>>>> manual).
>>>> Vy 73 de OZ1CCM Kel
>>>> Kjeld Holm
>