[Elecraft] K3 DATA A vs AFSK A

[Joe Subich, W4TV]

Note: in my comment below Mark-85 Hz should be MARK+85 Hz as AFSK A
(LSB) reverses the sense of the tones - Mark is the lower of the two
audio tones but the higher of the RF frequencies.

73,

    ... Joe, W4TV


On 2015-03-17 6:48 PM, Fred Jensen wrote:
> Hmmm ... this may be the first time Fred Cady's book has failed me.  I
> understand now "what" each mode does.  What's still not clear is "why
> would I choose one over the other?"  Operator/User manuals tend not to
> answer that question, they are understandably focused on exactly how to
> operate the equipment.
>
> I'm very sure that, when I first set up RTTY, I went to AFSK A because I
> knew what audio frequency shift keying was and I didn't know what DATA A
> was.  It all worked, so I never changed it or tried out the other
> choice.  I guess if AFSK A is LSB and works with MMTTY in its default
> configuration, then DATA A is USB and I'd have to reverse the tones in
> MMTTY.
>
> I'll leave it as I've been using it, it works so it obviously doesn't
> need fixing.  I was just curious.  I have my "pitch" set at 915 Hz, I
> can't hear 2,125 Hz.  Thanks Joe and Mike.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
> - www.cqp.org
>
> On 3/17/2015 10:07 AM, Joe Subich, W4TV wrote:
>>
>> On 2015-03-17 12:41 PM, Fred Jensen wrote:
>>  > Can you 'splain the difference between AFSK and DATA A?
>>
>> AFSK A and DATA A are both audio modes.  AFSK A uses LSB
>> and FC is set to MARK - 85 Hz (the center of the two RTTY
>> Tones).  DATA A is USB and FC is set to 1500 Hz (the center
>> of the transmit audio passband [200 - 2800 Hz]).
>>
>> AFSK A also allows use of the AFSK transmit filter (a tight
>> filter around the Mark/Space tones to eliminate hum/pops/etc.)
>> and the use of the Dual Tone filter on receive.
>
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