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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