HEY GUYS
When you guys get this 2Tone thing all figured out so it works with FSK
and N1MM then I'll try it again, All I get now is a continious tone.
I don't understand any of this ""OOK"" or such stuff.
Rex
----- Original Message -----
From: "Kok Chen" <chen@mac.com>
To: "RTTY Reflector" <rtty@contesting.com>
Cc: "Doug Faunt" <faunt@panix.com>
Sent: Monday, September 17, 2012 8:43 PM
Subject: Re: [RTTY] AFSK to FSK converter
On Sep 17, 2012, at 1:06 PM, Doug Faunt wrote:
And he may have been unaware of the OOK to FSK hack (which would work
with AFC on) and should be trivial to implement, just set one of the AFSK
output frequencies to zero.
Hah! I never thought of that -- turning AFSK into OOK by turning one
frequency of the tone pair to 0 Hz.
There could be just a small side effect: if the transmit AFSK tones are
generated in a phase continuous manner, the digital output to the sound
card will not be zero, but instead some constant DC level, until the OOK
tone resumes.
Sound cards don't put out DC (thus the "DC hump" problem with SDRs) and
who knows what they do with the DC during those OOK transitions. The OOK
decoder may end up with a small random jitter that varies from bit to bit.
There is another potential problem. If the tones are being generated
digitally by some DDA (digital differential analyzer) fashion, the delta-T
value for 0 Hz would cause an overflow. I guess this can be mitigated
with the use of 1 Hz instead of 0 Hz, and let the sound card suppress the
1 Hz signal.
73
Chen, W7AY
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