[RTTY] AFSK to FSK converter

[Rex Maner]

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 at mac.com>
To: "RTTY Reflector" <rtty at contesting.com>
Cc: "Doug Faunt" <faunt at 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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